jdk/src/share/classes/java/net/URLConnection.java
changeset 2 90ce3da70b43
child 83 34040312032d
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/net/URLConnection.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1767 @@
+/*
+ * Copyright 1995-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.net;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.Hashtable;
+import java.util.Date;
+import java.util.StringTokenizer;
+import java.util.Collections;
+import java.util.Map;
+import java.util.List;
+import java.security.Permission;
+import java.security.AccessController;
+import sun.security.util.SecurityConstants;
+import sun.net.www.MessageHeader;
+
+/**
+ * The abstract class <code>URLConnection</code> is the superclass
+ * of all classes that represent a communications link between the
+ * application and a URL. Instances of this class can be used both to
+ * read from and to write to the resource referenced by the URL. In
+ * general, creating a connection to a URL is a multistep process:
+ * <p>
+ * <center><table border=2 summary="Describes the process of creating a connection to a URL: openConnection() and connect() over time.">
+ * <tr><th><code>openConnection()</code></th>
+ *     <th><code>connect()</code></th></tr>
+ * <tr><td>Manipulate parameters that affect the connection to the remote
+ *         resource.</td>
+ *     <td>Interact with the resource; query header fields and
+ *         contents.</td></tr>
+ * </table>
+ * ----------------------------&gt;
+ * <br>time</center>
+ *
+ * <ol>
+ * <li>The connection object is created by invoking the
+ *     <code>openConnection</code> method on a URL.
+ * <li>The setup parameters and general request properties are manipulated.
+ * <li>The actual connection to the remote object is made, using the
+ *    <code>connect</code> method.
+ * <li>The remote object becomes available. The header fields and the contents
+ *     of the remote object can be accessed.
+ * </ol>
+ * <p>
+ * The setup parameters are modified using the following methods:
+ * <ul>
+ *   <li><code>setAllowUserInteraction</code>
+ *   <li><code>setDoInput</code>
+ *   <li><code>setDoOutput</code>
+ *   <li><code>setIfModifiedSince</code>
+ *   <li><code>setUseCaches</code>
+ * </ul>
+ * <p>
+ * and the general request properties are modified using the method:
+ * <ul>
+ *   <li><code>setRequestProperty</code>
+ * </ul>
+ * <p>
+ * Default values for the <code>AllowUserInteraction</code> and
+ * <code>UseCaches</code> parameters can be set using the methods
+ * <code>setDefaultAllowUserInteraction</code> and
+ * <code>setDefaultUseCaches</code>.
+ * <p>
+ * Each of the above <code>set</code> methods has a corresponding
+ * <code>get</code> method to retrieve the value of the parameter or
+ * general request property. The specific parameters and general
+ * request properties that are applicable are protocol specific.
+ * <p>
+ * The following methods are used to access the header fields and
+ * the contents after the connection is made to the remote object:
+ * <ul>
+ *   <li><code>getContent</code>
+ *   <li><code>getHeaderField</code>
+ *   <li><code>getInputStream</code>
+ *   <li><code>getOutputStream</code>
+ * </ul>
+ * <p>
+ * Certain header fields are accessed frequently. The methods:
+ * <ul>
+ *   <li><code>getContentEncoding</code>
+ *   <li><code>getContentLength</code>
+ *   <li><code>getContentType</code>
+ *   <li><code>getDate</code>
+ *   <li><code>getExpiration</code>
+ *   <li><code>getLastModifed</code>
+ * </ul>
+ * <p>
+ * provide convenient access to these fields. The
+ * <code>getContentType</code> method is used by the
+ * <code>getContent</code> method to determine the type of the remote
+ * object; subclasses may find it convenient to override the
+ * <code>getContentType</code> method.
+ * <p>
+ * In the common case, all of the pre-connection parameters and
+ * general request properties can be ignored: the pre-connection
+ * parameters and request properties default to sensible values. For
+ * most clients of this interface, there are only two interesting
+ * methods: <code>getInputStream</code> and <code>getContent</code>,
+ * which are mirrored in the <code>URL</code> class by convenience methods.
+ * <p>
+ * More information on the request properties and header fields of
+ * an <code>http</code> connection can be found at:
+ * <blockquote><pre>
+ * <a href="http://www.ietf.org/rfc/rfc2616.txt">http://www.ietf.org/rfc/rfc2616.txt</a>
+ * </pre></blockquote>
+ *
+ * Note about <code>fileNameMap</code>: In versions prior to JDK 1.1.6,
+ * field <code>fileNameMap</code> of <code>URLConnection</code> was public.
+ * In JDK 1.1.6 and later, <code>fileNameMap</code> is private; accessor
+ * and mutator methods {@link #getFileNameMap() getFileNameMap} and
+ * {@link #setFileNameMap(java.net.FileNameMap) setFileNameMap} are added
+ * to access it.  This change is also described on the <a href=
+ * "http://java.sun.com/products/jdk/1.2/compatibility.html">
+ * Compatibility</a> page.
+ *
+ * Invoking the <tt>close()</tt> methods on the <tt>InputStream</tt> or <tt>OutputStream</tt> of an
+ * <tt>URLConnection</tt> after a request may free network resources associated with this
+ * instance, unless particular protocol specifications specify different behaviours
+ * for it.
+ *
+ * @author  James Gosling
+ * @see     java.net.URL#openConnection()
+ * @see     java.net.URLConnection#connect()
+ * @see     java.net.URLConnection#getContent()
+ * @see     java.net.URLConnection#getContentEncoding()
+ * @see     java.net.URLConnection#getContentLength()
+ * @see     java.net.URLConnection#getContentType()
+ * @see     java.net.URLConnection#getDate()
+ * @see     java.net.URLConnection#getExpiration()
+ * @see     java.net.URLConnection#getHeaderField(int)
+ * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+ * @see     java.net.URLConnection#getInputStream()
+ * @see     java.net.URLConnection#getLastModified()
+ * @see     java.net.URLConnection#getOutputStream()
+ * @see     java.net.URLConnection#setAllowUserInteraction(boolean)
+ * @see     java.net.URLConnection#setDefaultUseCaches(boolean)
+ * @see     java.net.URLConnection#setDoInput(boolean)
+ * @see     java.net.URLConnection#setDoOutput(boolean)
+ * @see     java.net.URLConnection#setIfModifiedSince(long)
+ * @see     java.net.URLConnection#setRequestProperty(java.lang.String, java.lang.String)
+ * @see     java.net.URLConnection#setUseCaches(boolean)
+ * @since   JDK1.0
+ */
+public abstract class URLConnection {
+
+   /**
+     * The URL represents the remote object on the World Wide Web to
+     * which this connection is opened.
+     * <p>
+     * The value of this field can be accessed by the
+     * <code>getURL</code> method.
+     * <p>
+     * The default value of this variable is the value of the URL
+     * argument in the <code>URLConnection</code> constructor.
+     *
+     * @see     java.net.URLConnection#getURL()
+     * @see     java.net.URLConnection#url
+     */
+    protected URL url;
+
+   /**
+     * This variable is set by the <code>setDoInput</code> method. Its
+     * value is returned by the <code>getDoInput</code> method.
+     * <p>
+     * A URL connection can be used for input and/or output. Setting the
+     * <code>doInput</code> flag to <code>true</code> indicates that
+     * the application intends to read data from the URL connection.
+     * <p>
+     * The default value of this field is <code>true</code>.
+     *
+     * @see     java.net.URLConnection#getDoInput()
+     * @see     java.net.URLConnection#setDoInput(boolean)
+     */
+    protected boolean doInput = true;
+
+   /**
+     * This variable is set by the <code>setDoOutput</code> method. Its
+     * value is returned by the <code>getDoOutput</code> method.
+     * <p>
+     * A URL connection can be used for input and/or output. Setting the
+     * <code>doOutput</code> flag to <code>true</code> indicates
+     * that the application intends to write data to the URL connection.
+     * <p>
+     * The default value of this field is <code>false</code>.
+     *
+     * @see     java.net.URLConnection#getDoOutput()
+     * @see     java.net.URLConnection#setDoOutput(boolean)
+     */
+    protected boolean doOutput = false;
+
+    private static boolean defaultAllowUserInteraction = false;
+
+   /**
+     * If <code>true</code>, this <code>URL</code> is being examined in
+     * a context in which it makes sense to allow user interactions such
+     * as popping up an authentication dialog. If <code>false</code>,
+     * then no user interaction is allowed.
+     * <p>
+     * The value of this field can be set by the
+     * <code>setAllowUserInteraction</code> method.
+     * Its value is returned by the
+     * <code>getAllowUserInteraction</code> method.
+     * Its default value is the value of the argument in the last invocation
+     * of the <code>setDefaultAllowUserInteraction</code> method.
+     *
+     * @see     java.net.URLConnection#getAllowUserInteraction()
+     * @see     java.net.URLConnection#setAllowUserInteraction(boolean)
+     * @see     java.net.URLConnection#setDefaultAllowUserInteraction(boolean)
+     */
+    protected boolean allowUserInteraction = defaultAllowUserInteraction;
+
+    private static boolean defaultUseCaches = true;
+
+   /**
+     * If <code>true</code>, the protocol is allowed to use caching
+     * whenever it can. If <code>false</code>, the protocol must always
+     * try to get a fresh copy of the object.
+     * <p>
+     * This field is set by the <code>setUseCaches</code> method. Its
+     * value is returned by the <code>getUseCaches</code> method.
+     * <p>
+     * Its default value is the value given in the last invocation of the
+     * <code>setDefaultUseCaches</code> method.
+     *
+     * @see     java.net.URLConnection#setUseCaches(boolean)
+     * @see     java.net.URLConnection#getUseCaches()
+     * @see     java.net.URLConnection#setDefaultUseCaches(boolean)
+     */
+    protected boolean useCaches = defaultUseCaches;
+
+   /**
+     * Some protocols support skipping the fetching of the object unless
+     * the object has been modified more recently than a certain time.
+     * <p>
+     * A nonzero value gives a time as the number of milliseconds since
+     * January 1, 1970, GMT. The object is fetched only if it has been
+     * modified more recently than that time.
+     * <p>
+     * This variable is set by the <code>setIfModifiedSince</code>
+     * method. Its value is returned by the
+     * <code>getIfModifiedSince</code> method.
+     * <p>
+     * The default value of this field is <code>0</code>, indicating
+     * that the fetching must always occur.
+     *
+     * @see     java.net.URLConnection#getIfModifiedSince()
+     * @see     java.net.URLConnection#setIfModifiedSince(long)
+     */
+    protected long ifModifiedSince = 0;
+
+   /**
+     * If <code>false</code>, this connection object has not created a
+     * communications link to the specified URL. If <code>true</code>,
+     * the communications link has been established.
+     */
+    protected boolean connected = false;
+
+    /**
+     * @since 1.5
+     */
+    private int connectTimeout;
+    private int readTimeout;
+
+    /**
+     * @since 1.6
+     */
+    private MessageHeader requests;
+
+   /**
+    * @since   JDK1.1
+    */
+    private static FileNameMap fileNameMap;
+
+    /**
+     * @since 1.2.2
+     */
+    private static boolean fileNameMapLoaded = false;
+
+    /**
+     * Loads filename map (a mimetable) from a data file. It will
+     * first try to load the user-specific table, defined
+     * by &quot;content.types.user.table&quot; property. If that fails,
+     * it tries to load the default built-in table at
+     * lib/content-types.properties under java home.
+     *
+     * @return the FileNameMap
+     * @since 1.2
+     * @see #setFileNameMap(java.net.FileNameMap)
+     */
+    public static synchronized FileNameMap getFileNameMap() {
+        if ((fileNameMap == null) && !fileNameMapLoaded) {
+            fileNameMap = sun.net.www.MimeTable.loadTable();
+            fileNameMapLoaded = true;
+        }
+
+        return new FileNameMap() {
+            private FileNameMap map = fileNameMap;
+            public String getContentTypeFor(String fileName) {
+                return map.getContentTypeFor(fileName);
+            }
+        };
+    }
+
+    /**
+     * Sets the FileNameMap.
+     * <p>
+     * If there is a security manager, this method first calls
+     * the security manager's <code>checkSetFactory</code> method
+     * to ensure the operation is allowed.
+     * This could result in a SecurityException.
+     *
+     * @param map the FileNameMap to be set
+     * @exception  SecurityException  if a security manager exists and its
+     *             <code>checkSetFactory</code> method doesn't allow the operation.
+     * @see        SecurityManager#checkSetFactory
+     * @see #getFileNameMap()
+     * @since 1.2
+     */
+    public static void setFileNameMap(FileNameMap map) {
+        SecurityManager sm = System.getSecurityManager();
+        if (sm != null) sm.checkSetFactory();
+        fileNameMap = map;
+    }
+
+    /**
+     * Opens a communications link to the resource referenced by this
+     * URL, if such a connection has not already been established.
+     * <p>
+     * If the <code>connect</code> method is called when the connection
+     * has already been opened (indicated by the <code>connected</code>
+     * field having the value <code>true</code>), the call is ignored.
+     * <p>
+     * URLConnection objects go through two phases: first they are
+     * created, then they are connected.  After being created, and
+     * before being connected, various options can be specified
+     * (e.g., doInput and UseCaches).  After connecting, it is an
+     * error to try to set them.  Operations that depend on being
+     * connected, like getContentLength, will implicitly perform the
+     * connection, if necessary.
+     *
+     * @throws SocketTimeoutException if the timeout expires before
+     *               the connection can be established
+     * @exception  IOException  if an I/O error occurs while opening the
+     *               connection.
+     * @see java.net.URLConnection#connected
+     * @see #getConnectTimeout()
+     * @see #setConnectTimeout(int)
+     */
+    abstract public void connect() throws IOException;
+
+    /**
+     * Sets a specified timeout value, in milliseconds, to be used
+     * when opening a communications link to the resource referenced
+     * by this URLConnection.  If the timeout expires before the
+     * connection can be established, a
+     * java.net.SocketTimeoutException is raised. A timeout of zero is
+     * interpreted as an infinite timeout.
+
+     * <p> Some non-standard implmentation of this method may ignore
+     * the specified timeout. To see the connect timeout set, please
+     * call getConnectTimeout().
+     *
+     * @param timeout an <code>int</code> that specifies the connect
+     *               timeout value in milliseconds
+     * @throws IllegalArgumentException if the timeout parameter is negative
+     *
+     * @see #getConnectTimeout()
+     * @see #connect()
+     * @since 1.5
+     */
+    public void setConnectTimeout(int timeout) {
+        if (timeout < 0) {
+            throw new IllegalArgumentException("timeout can not be negative");
+        }
+        connectTimeout = timeout;
+    }
+
+    /**
+     * Returns setting for connect timeout.
+     * <p>
+     * 0 return implies that the option is disabled
+     * (i.e., timeout of infinity).
+     *
+     * @return an <code>int</code> that indicates the connect timeout
+     *         value in milliseconds
+     * @see #setConnectTimeout(int)
+     * @see #connect()
+     * @since 1.5
+     */
+    public int getConnectTimeout() {
+        return connectTimeout;
+    }
+
+    /**
+     * Sets the read timeout to a specified timeout, in
+     * milliseconds. A non-zero value specifies the timeout when
+     * reading from Input stream when a connection is established to a
+     * resource. If the timeout expires before there is data available
+     * for read, a java.net.SocketTimeoutException is raised. A
+     * timeout of zero is interpreted as an infinite timeout.
+     *
+     *<p> Some non-standard implementation of this method ignores the
+     * specified timeout. To see the read timeout set, please call
+     * getReadTimeout().
+     *
+     * @param timeout an <code>int</code> that specifies the timeout
+     * value to be used in milliseconds
+     * @throws IllegalArgumentException if the timeout parameter is negative
+     *
+     * @see #getReadTimeout()
+     * @see InputStream#read()
+     * @since 1.5
+     */
+    public void setReadTimeout(int timeout) {
+        if (timeout < 0) {
+            throw new IllegalArgumentException("timeout can not be negative");
+        }
+        readTimeout = timeout;
+    }
+
+    /**
+     * Returns setting for read timeout. 0 return implies that the
+     * option is disabled (i.e., timeout of infinity).
+     *
+     * @return an <code>int</code> that indicates the read timeout
+     *         value in milliseconds
+     *
+     * @see #setReadTimeout(int)
+     * @see InputStream#read()
+     * @since 1.5
+     */
+    public int getReadTimeout() {
+        return readTimeout;
+    }
+
+    /**
+     * Constructs a URL connection to the specified URL. A connection to
+     * the object referenced by the URL is not created.
+     *
+     * @param   url   the specified URL.
+     */
+    protected URLConnection(URL url) {
+        this.url = url;
+    }
+
+    /**
+     * Returns the value of this <code>URLConnection</code>'s <code>URL</code>
+     * field.
+     *
+     * @return  the value of this <code>URLConnection</code>'s <code>URL</code>
+     *          field.
+     * @see     java.net.URLConnection#url
+     */
+    public URL getURL() {
+        return url;
+    }
+
+    /**
+     * Returns the value of the <code>content-length</code> header field.
+     * <P>
+     * <B>Note</B>: {@link #getContentLengthLong() getContentLengthLong()}
+     * should be preferred over this method, since it returns a {@code long}
+     * instead and is therefore more portable.</P>
+     *
+     * @return  the content length of the resource that this connection's URL
+     *          references, {@code -1} if the content length is not known,
+     *          or if the content length is greater than Integer.MAX_VALUE.
+     */
+    public int getContentLength() {
+        long l = getContentLengthLong();
+        if (l > Integer.MAX_VALUE)
+            return -1;
+        return (int) l;
+    }
+
+    /**
+     * Returns the value of the <code>content-length</code> header field as a
+     * long.
+     *
+     * @return  the content length of the resource that this connection's URL
+     *          references, or <code>-1</code> if the content length is
+     *          not known.
+     * @since 7.0
+     */
+    public long getContentLengthLong() {
+        return getHeaderFieldLong("content-length", -1);
+    }
+
+    /**
+     * Returns the value of the <code>content-type</code> header field.
+     *
+     * @return  the content type of the resource that the URL references,
+     *          or <code>null</code> if not known.
+     * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+     */
+    public String getContentType() {
+        return getHeaderField("content-type");
+    }
+
+    /**
+     * Returns the value of the <code>content-encoding</code> header field.
+     *
+     * @return  the content encoding of the resource that the URL references,
+     *          or <code>null</code> if not known.
+     * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+     */
+    public String getContentEncoding() {
+        return getHeaderField("content-encoding");
+    }
+
+    /**
+     * Returns the value of the <code>expires</code> header field.
+     *
+     * @return  the expiration date of the resource that this URL references,
+     *          or 0 if not known. The value is the number of milliseconds since
+     *          January 1, 1970 GMT.
+     * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+     */
+    public long getExpiration() {
+        return getHeaderFieldDate("expires", 0);
+    }
+
+    /**
+     * Returns the value of the <code>date</code> header field.
+     *
+     * @return  the sending date of the resource that the URL references,
+     *          or <code>0</code> if not known. The value returned is the
+     *          number of milliseconds since January 1, 1970 GMT.
+     * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+     */
+    public long getDate() {
+        return getHeaderFieldDate("date", 0);
+    }
+
+    /**
+     * Returns the value of the <code>last-modified</code> header field.
+     * The result is the number of milliseconds since January 1, 1970 GMT.
+     *
+     * @return  the date the resource referenced by this
+     *          <code>URLConnection</code> was last modified, or 0 if not known.
+     * @see     java.net.URLConnection#getHeaderField(java.lang.String)
+     */
+    public long getLastModified() {
+        return getHeaderFieldDate("last-modified", 0);
+    }
+
+    /**
+     * Returns the value of the named header field.
+     * <p>
+     * If called on a connection that sets the same header multiple times
+     * with possibly different values, only the last value is returned.
+     *
+     *
+     * @param   name   the name of a header field.
+     * @return  the value of the named header field, or <code>null</code>
+     *          if there is no such field in the header.
+     */
+    public String getHeaderField(String name) {
+        return null;
+    }
+
+    /**
+     * Returns an unmodifiable Map of the header fields.
+     * The Map keys are Strings that represent the
+     * response-header field names. Each Map value is an
+     * unmodifiable List of Strings that represents
+     * the corresponding field values.
+     *
+     * @return a Map of header fields
+     * @since 1.4
+     */
+    public Map<String,List<String>> getHeaderFields() {
+        return Collections.EMPTY_MAP;
+    }
+
+    /**
+     * Returns the value of the named field parsed as a number.
+     * <p>
+     * This form of <code>getHeaderField</code> exists because some
+     * connection types (e.g., <code>http-ng</code>) have pre-parsed
+     * headers. Classes for that connection type can override this method
+     * and short-circuit the parsing.
+     *
+     * @param   name      the name of the header field.
+     * @param   Default   the default value.
+     * @return  the value of the named field, parsed as an integer. The
+     *          <code>Default</code> value is returned if the field is
+     *          missing or malformed.
+     */
+    public int getHeaderFieldInt(String name, int Default) {
+        String value = getHeaderField(name);
+        try {
+            return Integer.parseInt(value);
+        } catch (Exception e) { }
+        return Default;
+    }
+
+    /**
+     * Returns the value of the named field parsed as a number.
+     * <p>
+     * This form of <code>getHeaderField</code> exists because some
+     * connection types (e.g., <code>http-ng</code>) have pre-parsed
+     * headers. Classes for that connection type can override this method
+     * and short-circuit the parsing.
+     *
+     * @param   name      the name of the header field.
+     * @param   Default   the default value.
+     * @return  the value of the named field, parsed as a long. The
+     *          <code>Default</code> value is returned if the field is
+     *          missing or malformed.
+     * @since 7.0
+     */
+    public long getHeaderFieldLong(String name, long Default) {
+        String value = getHeaderField(name);
+        try {
+            return Long.parseLong(value);
+        } catch (Exception e) { }
+        return Default;
+    }
+
+    /**
+     * Returns the value of the named field parsed as date.
+     * The result is the number of milliseconds since January 1, 1970 GMT
+     * represented by the named field.
+     * <p>
+     * This form of <code>getHeaderField</code> exists because some
+     * connection types (e.g., <code>http-ng</code>) have pre-parsed
+     * headers. Classes for that connection type can override this method
+     * and short-circuit the parsing.
+     *
+     * @param   name     the name of the header field.
+     * @param   Default   a default value.
+     * @return  the value of the field, parsed as a date. The value of the
+     *          <code>Default</code> argument is returned if the field is
+     *          missing or malformed.
+     */
+    public long getHeaderFieldDate(String name, long Default) {
+        String value = getHeaderField(name);
+        try {
+            return Date.parse(value);
+        } catch (Exception e) { }
+        return Default;
+    }
+
+    /**
+     * Returns the key for the <code>n</code><sup>th</sup> header field.
+     * It returns <code>null</code> if there are fewer than <code>n+1</code> fields.
+     *
+     * @param   n   an index, where n>=0
+     * @return  the key for the <code>n</code><sup>th</sup> header field,
+     *          or <code>null</code> if there are fewer than <code>n+1</code>
+     *          fields.
+     */
+    public String getHeaderFieldKey(int n) {
+        return null;
+    }
+
+    /**
+     * Returns the value for the <code>n</code><sup>th</sup> header field.
+     * It returns <code>null</code> if there are fewer than
+     * <code>n+1</code>fields.
+     * <p>
+     * This method can be used in conjunction with the
+     * {@link #getHeaderFieldKey(int) getHeaderFieldKey} method to iterate through all
+     * the headers in the message.
+     *
+     * @param   n   an index, where n>=0
+     * @return  the value of the <code>n</code><sup>th</sup> header field
+     *          or <code>null</code> if there are fewer than <code>n+1</code> fields
+     * @see     java.net.URLConnection#getHeaderFieldKey(int)
+     */
+    public String getHeaderField(int n) {
+        return null;
+    }
+
+    /**
+     * Retrieves the contents of this URL connection.
+     * <p>
+     * This method first determines the content type of the object by
+     * calling the <code>getContentType</code> method. If this is
+     * the first time that the application has seen that specific content
+     * type, a content handler for that content type is created:
+     * <ol>
+     * <li>If the application has set up a content handler factory instance
+     *     using the <code>setContentHandlerFactory</code> method, the
+     *     <code>createContentHandler</code> method of that instance is called
+     *     with the content type as an argument; the result is a content
+     *     handler for that content type.
+     * <li>If no content handler factory has yet been set up, or if the
+     *     factory's <code>createContentHandler</code> method returns
+     *     <code>null</code>, then the application loads the class named:
+     *     <blockquote><pre>
+     *         sun.net.www.content.&lt;<i>contentType</i>&gt;
+     *     </pre></blockquote>
+     *     where &lt;<i>contentType</i>&gt; is formed by taking the
+     *     content-type string, replacing all slash characters with a
+     *     <code>period</code> ('.'), and all other non-alphanumeric characters
+     *     with the underscore character '<code>_</code>'. The alphanumeric
+     *     characters are specifically the 26 uppercase ASCII letters
+     *     '<code>A</code>' through '<code>Z</code>', the 26 lowercase ASCII
+     *     letters '<code>a</code>' through '<code>z</code>', and the 10 ASCII
+     *     digits '<code>0</code>' through '<code>9</code>'. If the specified
+     *     class does not exist, or is not a subclass of
+     *     <code>ContentHandler</code>, then an
+     *     <code>UnknownServiceException</code> is thrown.
+     * </ol>
+     *
+     * @return     the object fetched. The <code>instanceof</code> operator
+     *               should be used to determine the specific kind of object
+     *               returned.
+     * @exception  IOException              if an I/O error occurs while
+     *               getting the content.
+     * @exception  UnknownServiceException  if the protocol does not support
+     *               the content type.
+     * @see        java.net.ContentHandlerFactory#createContentHandler(java.lang.String)
+     * @see        java.net.URLConnection#getContentType()
+     * @see        java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
+     */
+    public Object getContent() throws IOException {
+        // Must call getInputStream before GetHeaderField gets called
+        // so that FileNotFoundException has a chance to be thrown up
+        // from here without being caught.
+        getInputStream();
+        return getContentHandler().getContent(this);
+    }
+
+    /**
+     * Retrieves the contents of this URL connection.
+     *
+     * @param classes the <code>Class</code> array
+     * indicating the requested types
+     * @return     the object fetched that is the first match of the type
+     *               specified in the classes array. null if none of
+     *               the requested types are supported.
+     *               The <code>instanceof</code> operator should be used to
+     *               determine the specific kind of object returned.
+     * @exception  IOException              if an I/O error occurs while
+     *               getting the content.
+     * @exception  UnknownServiceException  if the protocol does not support
+     *               the content type.
+     * @see        java.net.URLConnection#getContent()
+     * @see        java.net.ContentHandlerFactory#createContentHandler(java.lang.String)
+     * @see        java.net.URLConnection#getContent(java.lang.Class[])
+     * @see        java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
+     * @since 1.3
+     */
+    public Object getContent(Class[] classes) throws IOException {
+        // Must call getInputStream before GetHeaderField gets called
+        // so that FileNotFoundException has a chance to be thrown up
+        // from here without being caught.
+        getInputStream();
+        return getContentHandler().getContent(this, classes);
+    }
+
+    /**
+     * Returns a permission object representing the permission
+     * necessary to make the connection represented by this
+     * object. This method returns null if no permission is
+     * required to make the connection. By default, this method
+     * returns <code>java.security.AllPermission</code>. Subclasses
+     * should override this method and return the permission
+     * that best represents the permission required to make a
+     * a connection to the URL. For example, a <code>URLConnection</code>
+     * representing a <code>file:</code> URL would return a
+     * <code>java.io.FilePermission</code> object.
+     *
+     * <p>The permission returned may dependent upon the state of the
+     * connection. For example, the permission before connecting may be
+     * different from that after connecting. For example, an HTTP
+     * sever, say foo.com, may redirect the connection to a different
+     * host, say bar.com. Before connecting the permission returned by
+     * the connection will represent the permission needed to connect
+     * to foo.com, while the permission returned after connecting will
+     * be to bar.com.
+     *
+     * <p>Permissions are generally used for two purposes: to protect
+     * caches of objects obtained through URLConnections, and to check
+     * the right of a recipient to learn about a particular URL. In
+     * the first case, the permission should be obtained
+     * <em>after</em> the object has been obtained. For example, in an
+     * HTTP connection, this will represent the permission to connect
+     * to the host from which the data was ultimately fetched. In the
+     * second case, the permission should be obtained and tested
+     * <em>before</em> connecting.
+     *
+     * @return the permission object representing the permission
+     * necessary to make the connection represented by this
+     * URLConnection.
+     *
+     * @exception IOException if the computation of the permission
+     * requires network or file I/O and an exception occurs while
+     * computing it.
+     */
+    public Permission getPermission() throws IOException {
+        return SecurityConstants.ALL_PERMISSION;
+    }
+
+    /**
+     * Returns an input stream that reads from this open connection.
+     *
+     * A SocketTimeoutException can be thrown when reading from the
+     * returned input stream if the read timeout expires before data
+     * is available for read.
+     *
+     * @return     an input stream that reads from this open connection.
+     * @exception  IOException              if an I/O error occurs while
+     *               creating the input stream.
+     * @exception  UnknownServiceException  if the protocol does not support
+     *               input.
+     * @see #setReadTimeout(int)
+     * @see #getReadTimeout()
+     */
+    public InputStream getInputStream() throws IOException {
+        throw new UnknownServiceException("protocol doesn't support input");
+    }
+
+    /**
+     * Returns an output stream that writes to this connection.
+     *
+     * @return     an output stream that writes to this connection.
+     * @exception  IOException              if an I/O error occurs while
+     *               creating the output stream.
+     * @exception  UnknownServiceException  if the protocol does not support
+     *               output.
+     */
+    public OutputStream getOutputStream() throws IOException {
+        throw new UnknownServiceException("protocol doesn't support output");
+    }
+
+    /**
+     * Returns a <code>String</code> representation of this URL connection.
+     *
+     * @return  a string representation of this <code>URLConnection</code>.
+     */
+    public String toString() {
+        return this.getClass().getName() + ":" + url;
+    }
+
+    /**
+     * Sets the value of the <code>doInput</code> field for this
+     * <code>URLConnection</code> to the specified value.
+     * <p>
+     * A URL connection can be used for input and/or output.  Set the DoInput
+     * flag to true if you intend to use the URL connection for input,
+     * false if not.  The default is true.
+     *
+     * @param   doinput   the new value.
+     * @throws IllegalStateException if already connected
+     * @see     java.net.URLConnection#doInput
+     * @see #getDoInput()
+     */
+    public void setDoInput(boolean doinput) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        doInput = doinput;
+    }
+
+    /**
+     * Returns the value of this <code>URLConnection</code>'s
+     * <code>doInput</code> flag.
+     *
+     * @return  the value of this <code>URLConnection</code>'s
+     *          <code>doInput</code> flag.
+     * @see     #setDoInput(boolean)
+     */
+    public boolean getDoInput() {
+        return doInput;
+    }
+
+    /**
+     * Sets the value of the <code>doOutput</code> field for this
+     * <code>URLConnection</code> to the specified value.
+     * <p>
+     * A URL connection can be used for input and/or output.  Set the DoOutput
+     * flag to true if you intend to use the URL connection for output,
+     * false if not.  The default is false.
+     *
+     * @param   dooutput   the new value.
+     * @throws IllegalStateException if already connected
+     * @see #getDoOutput()
+     */
+    public void setDoOutput(boolean dooutput) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        doOutput = dooutput;
+    }
+
+    /**
+     * Returns the value of this <code>URLConnection</code>'s
+     * <code>doOutput</code> flag.
+     *
+     * @return  the value of this <code>URLConnection</code>'s
+     *          <code>doOutput</code> flag.
+     * @see     #setDoOutput(boolean)
+     */
+    public boolean getDoOutput() {
+        return doOutput;
+    }
+
+    /**
+     * Set the value of the <code>allowUserInteraction</code> field of
+     * this <code>URLConnection</code>.
+     *
+     * @param   allowuserinteraction   the new value.
+     * @throws IllegalStateException if already connected
+     * @see     #getAllowUserInteraction()
+     */
+    public void setAllowUserInteraction(boolean allowuserinteraction) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        allowUserInteraction = allowuserinteraction;
+    }
+
+    /**
+     * Returns the value of the <code>allowUserInteraction</code> field for
+     * this object.
+     *
+     * @return  the value of the <code>allowUserInteraction</code> field for
+     *          this object.
+     * @see     #setAllowUserInteraction(boolean)
+     */
+    public boolean getAllowUserInteraction() {
+        return allowUserInteraction;
+    }
+
+    /**
+     * Sets the default value of the
+     * <code>allowUserInteraction</code> field for all future
+     * <code>URLConnection</code> objects to the specified value.
+     *
+     * @param   defaultallowuserinteraction   the new value.
+     * @see     #getDefaultAllowUserInteraction()
+     */
+    public static void setDefaultAllowUserInteraction(boolean defaultallowuserinteraction) {
+        defaultAllowUserInteraction = defaultallowuserinteraction;
+    }
+
+    /**
+     * Returns the default value of the <code>allowUserInteraction</code>
+     * field.
+     * <p>
+     * Ths default is "sticky", being a part of the static state of all
+     * URLConnections.  This flag applies to the next, and all following
+     * URLConnections that are created.
+     *
+     * @return  the default value of the <code>allowUserInteraction</code>
+     *          field.
+     * @see     #setDefaultAllowUserInteraction(boolean)
+     */
+    public static boolean getDefaultAllowUserInteraction() {
+        return defaultAllowUserInteraction;
+    }
+
+    /**
+     * Sets the value of the <code>useCaches</code> field of this
+     * <code>URLConnection</code> to the specified value.
+     * <p>
+     * Some protocols do caching of documents.  Occasionally, it is important
+     * to be able to "tunnel through" and ignore the caches (e.g., the
+     * "reload" button in a browser).  If the UseCaches flag on a connection
+     * is true, the connection is allowed to use whatever caches it can.
+     *  If false, caches are to be ignored.
+     *  The default value comes from DefaultUseCaches, which defaults to
+     * true.
+     *
+     * @param usecaches a <code>boolean</code> indicating whether
+     * or not to allow caching
+     * @throws IllegalStateException if already connected
+     * @see #getUseCaches()
+     */
+    public void setUseCaches(boolean usecaches) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        useCaches = usecaches;
+    }
+
+    /**
+     * Returns the value of this <code>URLConnection</code>'s
+     * <code>useCaches</code> field.
+     *
+     * @return  the value of this <code>URLConnection</code>'s
+     *          <code>useCaches</code> field.
+     * @see #setUseCaches(boolean)
+     */
+    public boolean getUseCaches() {
+        return useCaches;
+    }
+
+    /**
+     * Sets the value of the <code>ifModifiedSince</code> field of
+     * this <code>URLConnection</code> to the specified value.
+     *
+     * @param   ifmodifiedsince   the new value.
+     * @throws IllegalStateException if already connected
+     * @see     #getIfModifiedSince()
+     */
+    public void setIfModifiedSince(long ifmodifiedsince) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        ifModifiedSince = ifmodifiedsince;
+    }
+
+    /**
+     * Returns the value of this object's <code>ifModifiedSince</code> field.
+     *
+     * @return  the value of this object's <code>ifModifiedSince</code> field.
+     * @see #setIfModifiedSince(long)
+     */
+    public long getIfModifiedSince() {
+        return ifModifiedSince;
+    }
+
+   /**
+     * Returns the default value of a <code>URLConnection</code>'s
+     * <code>useCaches</code> flag.
+     * <p>
+     * Ths default is "sticky", being a part of the static state of all
+     * URLConnections.  This flag applies to the next, and all following
+     * URLConnections that are created.
+     *
+     * @return  the default value of a <code>URLConnection</code>'s
+     *          <code>useCaches</code> flag.
+     * @see     #setDefaultUseCaches(boolean)
+     */
+    public boolean getDefaultUseCaches() {
+        return defaultUseCaches;
+    }
+
+   /**
+     * Sets the default value of the <code>useCaches</code> field to the
+     * specified value.
+     *
+     * @param   defaultusecaches   the new value.
+     * @see     #getDefaultUseCaches()
+     */
+    public void setDefaultUseCaches(boolean defaultusecaches) {
+        defaultUseCaches = defaultusecaches;
+    }
+
+    /**
+     * Sets the general request property. If a property with the key already
+     * exists, overwrite its value with the new value.
+     *
+     * <p> NOTE: HTTP requires all request properties which can
+     * legally have multiple instances with the same key
+     * to use a comma-seperated list syntax which enables multiple
+     * properties to be appended into a single property.
+     *
+     * @param   key     the keyword by which the request is known
+     *                  (e.g., "<code>accept</code>").
+     * @param   value   the value associated with it.
+     * @throws IllegalStateException if already connected
+     * @throws NullPointerException if key is <CODE>null</CODE>
+     * @see #getRequestProperty(java.lang.String)
+     */
+    public void setRequestProperty(String key, String value) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        if (key == null)
+            throw new NullPointerException ("key is null");
+
+        if (requests == null)
+            requests = new MessageHeader();
+
+        requests.set(key, value);
+    }
+
+    /**
+     * Adds a general request property specified by a
+     * key-value pair.  This method will not overwrite
+     * existing values associated with the same key.
+     *
+     * @param   key     the keyword by which the request is known
+     *                  (e.g., "<code>accept</code>").
+     * @param   value  the value associated with it.
+     * @throws IllegalStateException if already connected
+     * @throws NullPointerException if key is null
+     * @see #getRequestProperties()
+     * @since 1.4
+     */
+    public void addRequestProperty(String key, String value) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+        if (key == null)
+            throw new NullPointerException ("key is null");
+
+        if (requests == null)
+            requests = new MessageHeader();
+
+        requests.add(key, value);
+    }
+
+
+    /**
+     * Returns the value of the named general request property for this
+     * connection.
+     *
+     * @param key the keyword by which the request is known (e.g., "accept").
+     * @return  the value of the named general request property for this
+     *           connection. If key is null, then null is returned.
+     * @throws IllegalStateException if already connected
+     * @see #setRequestProperty(java.lang.String, java.lang.String)
+     */
+    public String getRequestProperty(String key) {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+
+        if (requests == null)
+            return null;
+
+        return requests.findValue(key);
+    }
+
+    /**
+     * Returns an unmodifiable Map of general request
+     * properties for this connection. The Map keys
+     * are Strings that represent the request-header
+     * field names. Each Map value is a unmodifiable List
+     * of Strings that represents the corresponding
+     * field values.
+     *
+     * @return  a Map of the general request properties for this connection.
+     * @throws IllegalStateException if already connected
+     * @since 1.4
+     */
+    public Map<String,List<String>> getRequestProperties() {
+        if (connected)
+            throw new IllegalStateException("Already connected");
+
+        if (requests == null)
+            return Collections.EMPTY_MAP;
+
+        return requests.getHeaders(null);
+    }
+
+    /**
+     * Sets the default value of a general request property. When a
+     * <code>URLConnection</code> is created, it is initialized with
+     * these properties.
+     *
+     * @param   key     the keyword by which the request is known
+     *                  (e.g., "<code>accept</code>").
+     * @param   value   the value associated with the key.
+     *
+     * @see java.net.URLConnection#setRequestProperty(java.lang.String,java.lang.String)
+     *
+     * @deprecated The instance specific setRequestProperty method
+     * should be used after an appropriate instance of URLConnection
+     * is obtained. Invoking this method will have no effect.
+     *
+     * @see #getDefaultRequestProperty(java.lang.String)
+     */
+    @Deprecated
+    public static void setDefaultRequestProperty(String key, String value) {
+    }
+
+    /**
+     * Returns the value of the default request property. Default request
+     * properties are set for every connection.
+     *
+     * @param key the keyword by which the request is known (e.g., "accept").
+     * @return  the value of the default request property
+     * for the specified key.
+     *
+     * @see java.net.URLConnection#getRequestProperty(java.lang.String)
+     *
+     * @deprecated The instance specific getRequestProperty method
+     * should be used after an appropriate instance of URLConnection
+     * is obtained.
+     *
+     * @see #setDefaultRequestProperty(java.lang.String, java.lang.String)
+     */
+    @Deprecated
+    public static String getDefaultRequestProperty(String key) {
+        return null;
+    }
+
+    /**
+     * The ContentHandler factory.
+     */
+    static ContentHandlerFactory factory;
+
+    /**
+     * Sets the <code>ContentHandlerFactory</code> of an
+     * application. It can be called at most once by an application.
+     * <p>
+     * The <code>ContentHandlerFactory</code> instance is used to
+     * construct a content handler from a content type
+     * <p>
+     * If there is a security manager, this method first calls
+     * the security manager's <code>checkSetFactory</code> method
+     * to ensure the operation is allowed.
+     * This could result in a SecurityException.
+     *
+     * @param      fac   the desired factory.
+     * @exception  Error  if the factory has already been defined.
+     * @exception  SecurityException  if a security manager exists and its
+     *             <code>checkSetFactory</code> method doesn't allow the operation.
+     * @see        java.net.ContentHandlerFactory
+     * @see        java.net.URLConnection#getContent()
+     * @see        SecurityManager#checkSetFactory
+     */
+    public static synchronized void setContentHandlerFactory(ContentHandlerFactory fac) {
+        if (factory != null) {
+            throw new Error("factory already defined");
+        }
+        SecurityManager security = System.getSecurityManager();
+        if (security != null) {
+            security.checkSetFactory();
+        }
+        factory = fac;
+    }
+
+    private static Hashtable handlers = new Hashtable();
+    private static final ContentHandler UnknownContentHandlerP = new UnknownContentHandler();
+
+    /**
+     * Gets the Content Handler appropriate for this connection.
+     * @param connection the connection to use.
+     */
+    synchronized ContentHandler getContentHandler()
+    throws UnknownServiceException
+    {
+        String contentType = stripOffParameters(getContentType());
+        ContentHandler handler = null;
+        if (contentType == null)
+            throw new UnknownServiceException("no content-type");
+        try {
+            handler = (ContentHandler) handlers.get(contentType);
+            if (handler != null)
+                return handler;
+        } catch(Exception e) {
+        }
+
+        if (factory != null)
+            handler = factory.createContentHandler(contentType);
+        if (handler == null) {
+            try {
+                handler = lookupContentHandlerClassFor(contentType);
+            } catch(Exception e) {
+                e.printStackTrace();
+                handler = UnknownContentHandlerP;
+            }
+            handlers.put(contentType, handler);
+        }
+        return handler;
+    }
+
+    /*
+     * Media types are in the format: type/subtype*(; parameter).
+     * For looking up the content handler, we should ignore those
+     * parameters.
+     */
+    private String stripOffParameters(String contentType)
+    {
+        if (contentType == null)
+            return null;
+        int index = contentType.indexOf(';');
+
+        if (index > 0)
+            return contentType.substring(0, index);
+        else
+            return contentType;
+    }
+
+    private static final String contentClassPrefix = "sun.net.www.content";
+    private static final String contentPathProp = "java.content.handler.pkgs";
+
+    /**
+     * Looks for a content handler in a user-defineable set of places.
+     * By default it looks in sun.net.www.content, but users can define a
+     * vertical-bar delimited set of class prefixes to search through in
+     * addition by defining the java.content.handler.pkgs property.
+     * The class name must be of the form:
+     * <pre>
+     *     {package-prefix}.{major}.{minor}
+     * e.g.
+     *     YoyoDyne.experimental.text.plain
+     * </pre>
+     */
+    private ContentHandler lookupContentHandlerClassFor(String contentType)
+        throws InstantiationException, IllegalAccessException, ClassNotFoundException {
+        String contentHandlerClassName = typeToPackageName(contentType);
+
+        String contentHandlerPkgPrefixes =getContentHandlerPkgPrefixes();
+
+        StringTokenizer packagePrefixIter =
+            new StringTokenizer(contentHandlerPkgPrefixes, "|");
+
+        while (packagePrefixIter.hasMoreTokens()) {
+            String packagePrefix = packagePrefixIter.nextToken().trim();
+
+            try {
+                String clsName = packagePrefix + "." + contentHandlerClassName;
+                Class cls = null;
+                try {
+                    cls = Class.forName(clsName);
+                } catch (ClassNotFoundException e) {
+                    ClassLoader cl = ClassLoader.getSystemClassLoader();
+                    if (cl != null) {
+                        cls = cl.loadClass(clsName);
+                    }
+                }
+                if (cls != null) {
+                    ContentHandler handler =
+                        (ContentHandler)cls.newInstance();
+                    return handler;
+                }
+            } catch(Exception e) {
+            }
+        }
+
+        return UnknownContentHandlerP;
+    }
+
+    /**
+     * Utility function to map a MIME content type into an equivalent
+     * pair of class name components.  For example: "text/html" would
+     * be returned as "text.html"
+     */
+    private String typeToPackageName(String contentType) {
+        // make sure we canonicalize the class name: all lower case
+        contentType = contentType.toLowerCase();
+        int len = contentType.length();
+        char nm[] = new char[len];
+        contentType.getChars(0, len, nm, 0);
+        for (int i = 0; i < len; i++) {
+            char c = nm[i];
+            if (c == '/') {
+                nm[i] = '.';
+            } else if (!('A' <= c && c <= 'Z' ||
+                       'a' <= c && c <= 'z' ||
+                       '0' <= c && c <= '9')) {
+                nm[i] = '_';
+            }
+        }
+        return new String(nm);
+    }
+
+
+    /**
+     * Returns a vertical bar separated list of package prefixes for potential
+     * content handlers.  Tries to get the java.content.handler.pkgs property
+     * to use as a set of package prefixes to search.  Whether or not
+     * that property has been defined, the sun.net.www.content is always
+     * the last one on the returned package list.
+     */
+    private String getContentHandlerPkgPrefixes() {
+        String packagePrefixList = AccessController.doPrivileged(
+            new sun.security.action.GetPropertyAction(contentPathProp, ""));
+
+        if (packagePrefixList != "") {
+            packagePrefixList += "|";
+        }
+
+        return packagePrefixList + contentClassPrefix;
+    }
+
+    /**
+     * Tries to determine the content type of an object, based
+     * on the specified "file" component of a URL.
+     * This is a convenience method that can be used by
+     * subclasses that override the <code>getContentType</code> method.
+     *
+     * @param   fname   a filename.
+     * @return  a guess as to what the content type of the object is,
+     *          based upon its file name.
+     * @see     java.net.URLConnection#getContentType()
+     */
+    public static String guessContentTypeFromName(String fname) {
+        return getFileNameMap().getContentTypeFor(fname);
+    }
+
+    /**
+     * Tries to determine the type of an input stream based on the
+     * characters at the beginning of the input stream. This method can
+     * be used by subclasses that override the
+     * <code>getContentType</code> method.
+     * <p>
+     * Ideally, this routine would not be needed. But many
+     * <code>http</code> servers return the incorrect content type; in
+     * addition, there are many nonstandard extensions. Direct inspection
+     * of the bytes to determine the content type is often more accurate
+     * than believing the content type claimed by the <code>http</code> server.
+     *
+     * @param      is   an input stream that supports marks.
+     * @return     a guess at the content type, or <code>null</code> if none
+     *             can be determined.
+     * @exception  IOException  if an I/O error occurs while reading the
+     *               input stream.
+     * @see        java.io.InputStream#mark(int)
+     * @see        java.io.InputStream#markSupported()
+     * @see        java.net.URLConnection#getContentType()
+     */
+    static public String guessContentTypeFromStream(InputStream is)
+                        throws IOException {
+        // If we can't read ahead safely, just give up on guessing
+        if (!is.markSupported())
+            return null;
+
+        is.mark(12);
+        int c1 = is.read();
+        int c2 = is.read();
+        int c3 = is.read();
+        int c4 = is.read();
+        int c5 = is.read();
+        int c6 = is.read();
+        int c7 = is.read();
+        int c8 = is.read();
+        int c9 = is.read();
+        int c10 = is.read();
+        int c11 = is.read();
+        is.reset();
+
+        if (c1 == 0xCA && c2 == 0xFE && c3 == 0xBA && c4 == 0xBE) {
+            return "application/java-vm";
+        }
+
+        if (c1 == 0xAC && c2 == 0xED) {
+            // next two bytes are version number, currently 0x00 0x05
+            return "application/x-java-serialized-object";
+        }
+
+        if (c1 == '<') {
+            if (c2 == '!'
+                || ((c2 == 'h' && (c3 == 't' && c4 == 'm' && c5 == 'l' ||
+                                   c3 == 'e' && c4 == 'a' && c5 == 'd') ||
+                (c2 == 'b' && c3 == 'o' && c4 == 'd' && c5 == 'y'))) ||
+                ((c2 == 'H' && (c3 == 'T' && c4 == 'M' && c5 == 'L' ||
+                                c3 == 'E' && c4 == 'A' && c5 == 'D') ||
+                (c2 == 'B' && c3 == 'O' && c4 == 'D' && c5 == 'Y')))) {
+                return "text/html";
+            }
+
+            if (c2 == '?' && c3 == 'x' && c4 == 'm' && c5 == 'l' && c6 == ' ') {
+                return "application/xml";
+            }
+        }
+
+        // big and little endian UTF-16 encodings, with byte order mark
+        if (c1 == 0xfe && c2 == 0xff) {
+            if (c3 == 0 && c4 == '<' && c5 == 0 && c6 == '?' &&
+                c7 == 0 && c8 == 'x') {
+                return "application/xml";
+            }
+        }
+
+        if (c1 == 0xff && c2 == 0xfe) {
+            if (c3 == '<' && c4 == 0 && c5 == '?' && c6 == 0 &&
+                c7 == 'x' && c8 == 0) {
+                return "application/xml";
+            }
+        }
+
+        if (c1 == 'G' && c2 == 'I' && c3 == 'F' && c4 == '8') {
+            return "image/gif";
+        }
+
+        if (c1 == '#' && c2 == 'd' && c3 == 'e' && c4 == 'f') {
+            return "image/x-bitmap";
+        }
+
+        if (c1 == '!' && c2 == ' ' && c3 == 'X' && c4 == 'P' &&
+                        c5 == 'M' && c6 == '2') {
+            return "image/x-pixmap";
+        }
+
+        if (c1 == 137 && c2 == 80 && c3 == 78 &&
+                c4 == 71 && c5 == 13 && c6 == 10 &&
+                c7 == 26 && c8 == 10) {
+            return "image/png";
+        }
+
+        if (c1 == 0xFF && c2 == 0xD8 && c3 == 0xFF) {
+            if (c4 == 0xE0) {
+                return "image/jpeg";
+            }
+
+            /**
+             * File format used by digital cameras to store images.
+             * Exif Format can be read by any application supporting
+             * JPEG. Exif Spec can be found at:
+             * http://www.pima.net/standards/it10/PIMA15740/Exif_2-1.PDF
+             */
+            if ((c4 == 0xE1) &&
+                (c7 == 'E' && c8 == 'x' && c9 == 'i' && c10 =='f' &&
+                 c11 == 0)) {
+                return "image/jpeg";
+            }
+
+            if (c4 == 0xEE) {
+                return "image/jpg";
+            }
+        }
+
+        if (c1 == 0xD0 && c2 == 0xCF && c3 == 0x11 && c4 == 0xE0 &&
+            c5 == 0xA1 && c6 == 0xB1 && c7 == 0x1A && c8 == 0xE1) {
+
+            /* Above is signature of Microsoft Structured Storage.
+             * Below this, could have tests for various SS entities.
+             * For now, just test for FlashPix.
+             */
+            if (checkfpx(is)) {
+                return "image/vnd.fpx";
+            }
+        }
+
+        if (c1 == 0x2E && c2 == 0x73 && c3 == 0x6E && c4 == 0x64) {
+            return "audio/basic";  // .au format, big endian
+        }
+
+        if (c1 == 0x64 && c2 == 0x6E && c3 == 0x73 && c4 == 0x2E) {
+            return "audio/basic";  // .au format, little endian
+        }
+
+        if (c1 == 'R' && c2 == 'I' && c3 == 'F' && c4 == 'F') {
+            /* I don't know if this is official but evidence
+             * suggests that .wav files start with "RIFF" - brown
+             */
+            return "audio/x-wav";
+        }
+        return null;
+    }
+
+    /**
+     * Check for FlashPix image data in InputStream is.  Return true if
+     * the stream has FlashPix data, false otherwise.  Before calling this
+     * method, the stream should have already been checked to be sure it
+     * contains Microsoft Structured Storage data.
+     */
+    static private boolean checkfpx(InputStream is) throws IOException {
+
+        /* Test for FlashPix image data in Microsoft Structured Storage format.
+         * In general, should do this with calls to an SS implementation.
+         * Lacking that, need to dig via offsets to get to the FlashPix
+         * ClassID.  Details:
+         *
+         * Offset to Fpx ClsID from beginning of stream should be:
+         *
+         * FpxClsidOffset = rootEntryOffset + clsidOffset
+         *
+         * where: clsidOffset = 0x50.
+         *        rootEntryOffset = headerSize + sectorSize*sectDirStart
+         *                          + 128*rootEntryDirectory
+         *
+         *        where:  headerSize = 0x200 (always)
+         *                sectorSize = 2 raised to power of uSectorShift,
+         *                             which is found in the header at
+         *                             offset 0x1E.
+         *                sectDirStart = found in the header at offset 0x30.
+         *                rootEntryDirectory = in general, should search for
+         *                                     directory labelled as root.
+         *                                     We will assume value of 0 (i.e.,
+         *                                     rootEntry is in first directory)
+         */
+
+        // Mark the stream so we can reset it. 0x100 is enough for the first
+        // few reads, but the mark will have to be reset and set again once
+        // the offset to the root directory entry is computed. That offset
+        // can be very large and isn't know until the stream has been read from
+        is.mark(0x100);
+
+        // Get the byte ordering located at 0x1E. 0xFE is Intel,
+        // 0xFF is other
+        long toSkip = (long)0x1C;
+        long posn;
+
+        if ((posn = skipForward(is, toSkip)) < toSkip) {
+          is.reset();
+          return false;
+        }
+
+        int c[] = new int[16];
+        if (readBytes(c, 2, is) < 0) {
+            is.reset();
+            return false;
+        }
+
+        int byteOrder = c[0];
+
+        posn+=2;
+        int uSectorShift;
+        if (readBytes(c, 2, is) < 0) {
+            is.reset();
+            return false;
+        }
+
+        if(byteOrder == 0xFE) {
+            uSectorShift = c[0];
+            uSectorShift += c[1] << 8;
+        }
+        else {
+            uSectorShift = c[0] << 8;
+            uSectorShift += c[1];
+        }
+
+        posn += 2;
+        toSkip = (long)0x30 - posn;
+        long skipped = 0;
+        if ((skipped = skipForward(is, toSkip)) < toSkip) {
+          is.reset();
+          return false;
+        }
+        posn += skipped;
+
+        if (readBytes(c, 4, is) < 0) {
+            is.reset();
+            return false;
+        }
+
+        int sectDirStart;
+        if(byteOrder == 0xFE) {
+            sectDirStart = c[0];
+            sectDirStart += c[1] << 8;
+            sectDirStart += c[2] << 16;
+            sectDirStart += c[3] << 24;
+        } else {
+            sectDirStart =  c[0] << 24;
+            sectDirStart += c[1] << 16;
+            sectDirStart += c[2] << 8;
+            sectDirStart += c[3];
+        }
+        posn += 4;
+        is.reset(); // Reset back to the beginning
+
+        toSkip = 0x200L + (long)(1<<uSectorShift)*sectDirStart + 0x50L;
+
+        // Sanity check!
+        if (toSkip < 0) {
+            return false;
+        }
+
+        /*
+         * How far can we skip? Is there any performance problem here?
+         * This skip can be fairly long, at least 0x4c650 in at least
+         * one case. Have to assume that the skip will fit in an int.
+         * Leave room to read whole root dir
+         */
+        is.mark((int)toSkip+0x30);
+
+        if ((skipForward(is, toSkip)) < toSkip) {
+            is.reset();
+            return false;
+        }
+
+        /* should be at beginning of ClassID, which is as follows
+         * (in Intel byte order):
+         *    00 67 61 56 54 C1 CE 11 85 53 00 AA 00 A1 F9 5B
+         *
+         * This is stored from Windows as long,short,short,char[8]
+         * so for byte order changes, the order only changes for
+         * the first 8 bytes in the ClassID.
+         *
+         * Test against this, ignoring second byte (Intel) since
+         * this could change depending on part of Fpx file we have.
+         */
+
+        if (readBytes(c, 16, is) < 0) {
+            is.reset();
+            return false;
+        }
+
+        // intel byte order
+        if (byteOrder == 0xFE &&
+            c[0] == 0x00 && c[2] == 0x61 && c[3] == 0x56 &&
+            c[4] == 0x54 && c[5] == 0xC1 && c[6] == 0xCE &&
+            c[7] == 0x11 && c[8] == 0x85 && c[9] == 0x53 &&
+            c[10]== 0x00 && c[11]== 0xAA && c[12]== 0x00 &&
+            c[13]== 0xA1 && c[14]== 0xF9 && c[15]== 0x5B) {
+            is.reset();
+            return true;
+        }
+
+        // non-intel byte order
+        else if (c[3] == 0x00 && c[1] == 0x61 && c[0] == 0x56 &&
+            c[5] == 0x54 && c[4] == 0xC1 && c[7] == 0xCE &&
+            c[6] == 0x11 && c[8] == 0x85 && c[9] == 0x53 &&
+            c[10]== 0x00 && c[11]== 0xAA && c[12]== 0x00 &&
+            c[13]== 0xA1 && c[14]== 0xF9 && c[15]== 0x5B) {
+            is.reset();
+            return true;
+        }
+        is.reset();
+        return false;
+    }
+
+    /**
+     * Tries to read the specified number of bytes from the stream
+     * Returns -1, If EOF is reached before len bytes are read, returns 0
+     * otherwise
+     */
+    static private int readBytes(int c[], int len, InputStream is)
+                throws IOException {
+
+        byte buf[] = new byte[len];
+        if (is.read(buf, 0, len) < len) {
+            return -1;
+        }
+
+        // fill the passed in int array
+        for (int i = 0; i < len; i++) {
+             c[i] = buf[i] & 0xff;
+        }
+        return 0;
+    }
+
+
+    /**
+     * Skips through the specified number of bytes from the stream
+     * until either EOF is reached, or the specified
+     * number of bytes have been skipped
+     */
+    static private long skipForward(InputStream is, long toSkip)
+                throws IOException {
+
+        long eachSkip = 0;
+        long skipped = 0;
+
+        while (skipped != toSkip) {
+            eachSkip = is.skip(toSkip - skipped);
+
+            // check if EOF is reached
+            if (eachSkip <= 0) {
+                if (is.read() == -1) {
+                    return skipped ;
+                } else {
+                    skipped++;
+                }
+            }
+            skipped += eachSkip;
+        }
+        return skipped;
+    }
+
+}
+
+
+class UnknownContentHandler extends ContentHandler {
+    public Object getContent(URLConnection uc) throws IOException {
+        return uc.getInputStream();
+    }
+}