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 * Copyright (c) 1995, 2014, Oracle and/or its affiliates. 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle 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,

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 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.net;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.security.PrivilegedAction;

import java.util.Hashtable;

import java.util.Date;

import java.util.Iterator;

import java.util.ServiceConfigurationError;

import java.util.ServiceLoader;

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} 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:

 *

 * <center><table border=2 summary="Describes the process of creating a connection to a URL: openConnection() and connect() over time.">

 * <tr><th>{@code openConnection()}</th>

 *     <th>{@code connect()}</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>

 * ---------------------------->

 * <br>time</center>

 *

 * <ol>

 * <li>The connection object is created by invoking the

 *     {@code openConnection} 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} 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}

 *   <li>{@code setDoInput}

 *   <li>{@code setDoOutput}

 *   <li>{@code setIfModifiedSince}

 *   <li>{@code setUseCaches}

 * </ul>

 * <p>

 * and the general request properties are modified using the method:

 * <ul>

 *   <li>{@code setRequestProperty}

 * </ul>

 * <p>

 * Default values for the {@code AllowUserInteraction} and

 * {@code UseCaches} parameters can be set using the methods

 * {@code setDefaultAllowUserInteraction} and

 * {@code setDefaultUseCaches}.

 * <p>

 * Each of the above {@code set} methods has a corresponding

 * {@code get} 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}

 *   <li>{@code getHeaderField}

 *   <li>{@code getInputStream}

 *   <li>{@code getOutputStream}

 * </ul>

 * <p>

 * Certain header fields are accessed frequently. The methods:

 * <ul>

 *   <li>{@code getContentEncoding}

 *   <li>{@code getContentLength}

 *   <li>{@code getContentType}

 *   <li>{@code getDate}

 *   <li>{@code getExpiration}

 *   <li>{@code getLastModified}

 * </ul>

 * <p>

 * provide convenient access to these fields. The

 * {@code getContentType} method is used by the

 * {@code getContent} method to determine the type of the remote

 * object; subclasses may find it convenient to override the

 * {@code getContentType} 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} and {@code getContent},

 * which are mirrored in the {@code URL} class by convenience methods.

 * <p>

 * More information on the request properties and header fields of

 * an {@code http} 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>

 *

 * Invoking the {@code close()} methods on the {@code InputStream} or {@code OutputStream} of an

 * {@code URLConnection} 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   1.0

 */

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} method.

     * <p>

     * The default value of this variable is the value of the URL

     * argument in the {@code URLConnection} constructor.

     *

     * @see     java.net.URLConnection#getURL()

     * @see     java.net.URLConnection#url

     */

    protected URL url;

   /**

     * This variable is set by the {@code setDoInput} method. Its

     * value is returned by the {@code getDoInput} method.

     * <p>

     * A URL connection can be used for input and/or output. Setting the

     * {@code doInput} flag to {@code true} indicates that

     * the application intends to read data from the URL connection.

     * <p>

     * The default value of this field is {@code true}.

     *

     * @see     java.net.URLConnection#getDoInput()

     * @see     java.net.URLConnection#setDoInput(boolean)

     */

    protected boolean doInput = true;

   /**

     * This variable is set by the {@code setDoOutput} method. Its

     * value is returned by the {@code getDoOutput} method.

     * <p>

     * A URL connection can be used for input and/or output. Setting the

     * {@code doOutput} flag to {@code true} indicates

     * that the application intends to write data to the URL connection.

     * <p>

     * The default value of this field is {@code false}.

     *

     * @see     java.net.URLConnection#getDoOutput()

     * @see     java.net.URLConnection#setDoOutput(boolean)

     */

    protected boolean doOutput = false;

    private static boolean defaultAllowUserInteraction = false;

   /**

     * If {@code true}, this {@code URL} 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},

     * then no user interaction is allowed.

     * <p>

     * The value of this field can be set by the

     * {@code setAllowUserInteraction} method.

     * Its value is returned by the

     * {@code getAllowUserInteraction} method.

     * Its default value is the value of the argument in the last invocation

     * of the {@code setDefaultAllowUserInteraction} 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}, the protocol is allowed to use caching

     * whenever it can. If {@code false}, the protocol must always

     * try to get a fresh copy of the object.

     * <p>

     * This field is set by the {@code setUseCaches} method. Its

     * value is returned by the {@code getUseCaches} method.

     * <p>

     * Its default value is the value given in the last invocation of the

     * {@code setDefaultUseCaches} 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}

     * method. Its value is returned by the

     * {@code getIfModifiedSince} method.

     * <p>

     * The default value of this field is {@code 0}, 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}, this connection object has not created a

     * communications link to the specified URL. If {@code true},

     * 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   1.1

    */

    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 "content.types.user.table" property. If that fails,

     * it tries to load the default built-in table.

     *

     * @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} 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} 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} method is called when the connection

     * has already been opened (indicated by the {@code connected}

     * field having the value {@code true}), 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)

     */

    /**

     * 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 implementation of this method may ignore

     * the specified timeout. To see the connect timeout set, please

     * call getConnectTimeout().

     *

     * @param timeout an {@code int} 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} 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} 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} 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}'s {@code URL}

     * field.

     *

     * @return  the value of this {@code URLConnection}'s {@code URL}

     *          field.

     * @see     java.net.URLConnection#url

     */

    public URL getURL() {

        return url;

    }

    /**

     * Returns the value of the {@code content-length} 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} header field as a

     * long.

     *

     * @return  the content length of the resource that this connection's URL

     *          references, or {@code -1} if the content length is

     *          not known.

     * @since 1.7

     */

    public long getContentLengthLong() {

        return getHeaderFieldLong("content-length", -1);

    }

    /**

     * Returns the value of the {@code content-type} header field.

     *

     * @return  the content type of the resource that the URL references,

     *          or {@code null} if not known.

     * @see     java.net.URLConnection#getHeaderField(java.lang.String)

     */