URLStreamHandler is the common
+ * superclass for all stream protocol handlers. A stream protocol
+ * handler knows how to make a connection for a particular protocol
+ * type, such as http, ftp, or
+ * gopher.
+ *
+ * In most cases, an instance of a URLStreamHandler
+ * subclass is not created directly by an application. Rather, the
+ * first time a protocol name is encountered when constructing a
+ * URL, the appropriate stream protocol handler is
+ * automatically loaded.
+ *
+ * @author James Gosling
+ * @see java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)
+ * @since JDK1.0
+ */
+public abstract class URLStreamHandler {
+ /**
+ * Opens a connection to the object referenced by the
+ * URL argument.
+ * This method should be overridden by a subclass.
+ *
+ *
If for the handler's protocol (such as HTTP or JAR), there
+ * exists a public, specialized URLConnection subclass belonging
+ * to one of the following packages or one of their subpackages:
+ * java.lang, java.io, java.util, java.net, the connection
+ * returned will be of that subclass. For example, for HTTP an
+ * HttpURLConnection will be returned, and for JAR a
+ * JarURLConnection will be returned.
+ *
+ * @param u the URL that this connects to.
+ * @return a URLConnection object for the URL.
+ * @exception IOException if an I/O error occurs while opening the
+ * connection.
+ */
+ abstract protected URLConnection openConnection(URL u) throws IOException;
+
+ /**
+ * Same as openConnection(URL), except that the connection will be
+ * made through the specified proxy; Protocol handlers that do not
+ * support proxying will ignore the proxy parameter and make a
+ * normal connection.
+ *
+ * Calling this method preempts the system's default ProxySelector
+ * settings.
+ *
+ * @param u the URL that this connects to.
+ * @param p the proxy through which the connection will be made.
+ * If direct connection is desired, Proxy.NO_PROXY
+ * should be specified.
+ * @return a URLConnection object for the URL.
+ * @exception IOException if an I/O error occurs while opening the
+ * connection.
+ * @exception IllegalArgumentException if either u or p is null,
+ * or p has the wrong type.
+ * @exception UnsupportedOperationException if the subclass that
+ * implements the protocol doesn't support this method.
+ * @since 1.5
+ */
+ protected URLConnection openConnection(URL u, Proxy p) throws IOException {
+ throw new UnsupportedOperationException("Method not implemented.");
+ }
+
+ /**
+ * Parses the string representation of a URL into a
+ * URL object.
+ *
+ * If there is any inherited context, then it has already been
+ * copied into the URL argument.
+ *
+ * The parseURL method of URLStreamHandler
+ * parses the string representation as if it were an
+ * http specification. Most URL protocol families have a
+ * similar parsing. A stream protocol handler for a protocol that has
+ * a different syntax must override this routine.
+ *
+ * @param u the URL to receive the result of parsing
+ * the spec.
+ * @param spec the String representing the URL that
+ * must be parsed.
+ * @param start the character index at which to begin parsing. This is
+ * just past the ':' (if there is one) that
+ * specifies the determination of the protocol name.
+ * @param limit the character position to stop parsing at. This is the
+ * end of the string or the position of the
+ * "#" character, if present. All information
+ * after the sharp sign indicates an anchor.
+ */
+ protected void parseURL(URL u, String spec, int start, int limit) {
+ // These fields may receive context content if this was relative URL
+ String protocol = u.getProtocol();
+ String authority = u.getAuthority();
+ String userInfo = u.getUserInfo();
+ String host = u.getHost();
+ int port = u.getPort();
+ String path = u.getPath();
+ String query = u.getQuery();
+
+ // This field has already been parsed
+ String ref = u.getRef();
+
+ boolean isRelPath = false;
+ boolean queryOnly = false;
+
+// FIX: should not assume query if opaque
+ // Strip off the query part
+ if (start < limit) {
+ int queryStart = spec.indexOf('?');
+ queryOnly = queryStart == start;
+ if ((queryStart != -1) && (queryStart < limit)) {
+ query = spec.substring(queryStart+1, limit);
+ if (limit > queryStart)
+ limit = queryStart;
+ spec = spec.substring(0, queryStart);
+ }
+ }
+
+ int i = 0;
+ // Parse the authority part if any
+ boolean isUNCName = (start <= limit - 4) &&
+ (spec.charAt(start) == '/') &&
+ (spec.charAt(start + 1) == '/') &&
+ (spec.charAt(start + 2) == '/') &&
+ (spec.charAt(start + 3) == '/');
+ if (!isUNCName && (start <= limit - 2) && (spec.charAt(start) == '/') &&
+ (spec.charAt(start + 1) == '/')) {
+ start += 2;
+ i = spec.indexOf('/', start);
+ if (i < 0) {
+ i = spec.indexOf('?', start);
+ if (i < 0)
+ i = limit;
+ }
+
+ host = authority = spec.substring(start, i);
+
+ int ind = authority.indexOf('@');
+ if (ind != -1) {
+ userInfo = authority.substring(0, ind);
+ host = authority.substring(ind+1);
+ } else {
+ userInfo = null;
+ }
+ if (host != null) {
+ // If the host is surrounded by [ and ] then its an IPv6
+ // literal address as specified in RFC2732
+ if (host.length()>0 && (host.charAt(0) == '[')) {
+ if ((ind = host.indexOf(']')) > 2) {
+
+ String nhost = host ;
+ host = nhost.substring(0,ind+1);
+ if (!IPAddressUtil.
+ isIPv6LiteralAddress(host.substring(1, ind))) {
+ throw new IllegalArgumentException(
+ "Invalid host: "+ host);
+ }
+
+ port = -1 ;
+ if (nhost.length() > ind+1) {
+ if (nhost.charAt(ind+1) == ':') {
+ ++ind ;
+ // port can be null according to RFC2396
+ if (nhost.length() > (ind + 1)) {
+ port = Integer.parseInt(nhost.substring(ind+1));
+ }
+ } else {
+ throw new IllegalArgumentException(
+ "Invalid authority field: " + authority);
+ }
+ }
+ } else {
+ throw new IllegalArgumentException(
+ "Invalid authority field: " + authority);
+ }
+ } else {
+ ind = host.indexOf(':');
+ port = -1;
+ if (ind >= 0) {
+ // port can be null according to RFC2396
+ if (host.length() > (ind + 1)) {
+ port = Integer.parseInt(host.substring(ind + 1));
+ }
+ host = host.substring(0, ind);
+ }
+ }
+ } else {
+ host = "";
+ }
+ if (port < -1)
+ throw new IllegalArgumentException("Invalid port number :" +
+ port);
+ start = i;
+ // If the authority is defined then the path is defined by the
+ // spec only; See RFC 2396 Section 5.2.4.
+ if (authority != null && authority.length() > 0)
+ path = "";
+ }
+
+ if (host == null) {
+ host = "";
+ }
+
+ // Parse the file path if any
+ if (start < limit) {
+ if (spec.charAt(start) == '/') {
+ path = spec.substring(start, limit);
+ } else if (path != null && path.length() > 0) {
+ isRelPath = true;
+ int ind = path.lastIndexOf('/');
+ String seperator = "";
+ if (ind == -1 && authority != null)
+ seperator = "/";
+ path = path.substring(0, ind + 1) + seperator +
+ spec.substring(start, limit);
+
+ } else {
+ String seperator = (authority != null) ? "/" : "";
+ path = seperator + spec.substring(start, limit);
+ }
+ } else if (queryOnly && path != null) {
+ int ind = path.lastIndexOf('/');
+ if (ind < 0)
+ ind = 0;
+ path = path.substring(0, ind) + "/";
+ }
+ if (path == null)
+ path = "";
+
+ if (isRelPath) {
+ // Remove embedded /./
+ while ((i = path.indexOf("/./")) >= 0) {
+ path = path.substring(0, i) + path.substring(i + 2);
+ }
+ // Remove embedded /../ if possible
+ i = 0;
+ while ((i = path.indexOf("/../", i)) >= 0) {
+ /*
+ * A "/../" will cancel the previous segment and itself,
+ * unless that segment is a "/../" itself
+ * i.e. "/a/b/../c" becomes "/a/c"
+ * but "/../../a" should stay unchanged
+ */
+ if (i > 0 && (limit = path.lastIndexOf('/', i - 1)) >= 0 &&
+ (path.indexOf("/../", limit) != 0)) {
+ path = path.substring(0, limit) + path.substring(i + 3);
+ i = 0;
+ } else {
+ i = i + 3;
+ }
+ }
+ // Remove trailing .. if possible
+ while (path.endsWith("/..")) {
+ i = path.indexOf("/..");
+ if ((limit = path.lastIndexOf('/', i - 1)) >= 0) {
+ path = path.substring(0, limit+1);
+ } else {
+ break;
+ }
+ }
+ // Remove starting .
+ if (path.startsWith("./") && path.length() > 2)
+ path = path.substring(2);
+
+ // Remove trailing .
+ if (path.endsWith("/."))
+ path = path.substring(0, path.length() -1);
+ }
+
+ setURL(u, protocol, host, port, authority, userInfo, path, query, ref);
+ }
+
+ /**
+ * Returns the default port for a URL parsed by this handler. This method
+ * is meant to be overidden by handlers with default port numbers.
+ * @return the default port for a URL parsed by this handler.
+ * @since 1.3
+ */
+ protected int getDefaultPort() {
+ return -1;
+ }
+
+ /**
+ * Provides the default equals calculation. May be overidden by handlers
+ * for other protocols that have different requirements for equals().
+ * This method requires that none of its arguments is null. This is
+ * guaranteed by the fact that it is only called by java.net.URL class.
+ * @param u1 a URL object
+ * @param u2 a URL object
+ * @return true if the two urls are
+ * considered equal, ie. they refer to the same
+ * fragment in the same file.
+ * @since 1.3
+ */
+ protected boolean equals(URL u1, URL u2) {
+ String ref1 = u1.getRef();
+ String ref2 = u2.getRef();
+ return (ref1 == ref2 || (ref1 != null && ref1.equals(ref2))) &&
+ sameFile(u1, u2);
+ }
+
+ /**
+ * Provides the default hash calculation. May be overidden by handlers for
+ * other protocols that have different requirements for hashCode
+ * calculation.
+ * @param u a URL object
+ * @return an int suitable for hash table indexing
+ * @since 1.3
+ */
+ protected int hashCode(URL u) {
+ int h = 0;
+
+ // Generate the protocol part.
+ String protocol = u.getProtocol();
+ if (protocol != null)
+ h += protocol.hashCode();
+
+ // Generate the host part.
+ InetAddress addr = getHostAddress(u);
+ if (addr != null) {
+ h += addr.hashCode();
+ } else {
+ String host = u.getHost();
+ if (host != null)
+ h += host.toLowerCase().hashCode();
+ }
+
+ // Generate the file part.
+ String file = u.getFile();
+ if (file != null)
+ h += file.hashCode();
+
+ // Generate the port part.
+ if (u.getPort() == -1)
+ h += getDefaultPort();
+ else
+ h += u.getPort();
+
+ // Generate the ref part.
+ String ref = u.getRef();
+ if (ref != null)
+ h += ref.hashCode();
+
+ return h;
+ }
+
+ /**
+ * Compare two urls to see whether they refer to the same file,
+ * i.e., having the same protocol, host, port, and path.
+ * This method requires that none of its arguments is null. This is
+ * guaranteed by the fact that it is only called indirectly
+ * by java.net.URL class.
+ * @param u1 a URL object
+ * @param u2 a URL object
+ * @return true if u1 and u2 refer to the same file
+ * @since 1.3
+ */
+ protected boolean sameFile(URL u1, URL u2) {
+ // Compare the protocols.
+ if (!((u1.getProtocol() == u2.getProtocol()) ||
+ (u1.getProtocol() != null &&
+ u1.getProtocol().equalsIgnoreCase(u2.getProtocol()))))
+ return false;
+
+ // Compare the files.
+ if (!(u1.getFile() == u2.getFile() ||
+ (u1.getFile() != null && u1.getFile().equals(u2.getFile()))))
+ return false;
+
+ // Compare the ports.
+ int port1, port2;
+ port1 = (u1.getPort() != -1) ? u1.getPort() : u1.handler.getDefaultPort();
+ port2 = (u2.getPort() != -1) ? u2.getPort() : u2.handler.getDefaultPort();
+ if (port1 != port2)
+ return false;
+
+ // Compare the hosts.
+ if (!hostsEqual(u1, u2))
+ return false;
+
+ return true;
+ }
+
+ /**
+ * Get the IP address of our host. An empty host field or a DNS failure
+ * will result in a null return.
+ *
+ * @param u a URL object
+ * @return an InetAddress representing the host
+ * IP address.
+ * @since 1.3
+ */
+ protected synchronized InetAddress getHostAddress(URL u) {
+ if (u.hostAddress != null)
+ return u.hostAddress;
+
+ String host = u.getHost();
+ if (host == null || host.equals("")) {
+ return null;
+ } else {
+ try {
+ u.hostAddress = InetAddress.getByName(host);
+ } catch (UnknownHostException ex) {
+ return null;
+ } catch (SecurityException se) {
+ return null;
+ }
+ }
+ return u.hostAddress;
+ }
+
+ /**
+ * Compares the host components of two URLs.
+ * @param u1 the URL of the first host to compare
+ * @param u2 the URL of the second host to compare
+ * @return true if and only if they
+ * are equal, false otherwise.
+ * @since 1.3
+ */
+ protected boolean hostsEqual(URL u1, URL u2) {
+ InetAddress a1 = getHostAddress(u1);
+ InetAddress a2 = getHostAddress(u2);
+ // if we have internet address for both, compare them
+ if (a1 != null && a2 != null) {
+ return a1.equals(a2);
+ // else, if both have host names, compare them
+ } else if (u1.getHost() != null && u2.getHost() != null)
+ return u1.getHost().equalsIgnoreCase(u2.getHost());
+ else
+ return u1.getHost() == null && u2.getHost() == null;
+ }
+
+ /**
+ * Converts a URL of a specific protocol to a
+ * String.
+ *
+ * @param u the URL.
+ * @return a string representation of the URL argument.
+ */
+ protected String toExternalForm(URL u) {
+
+ // pre-compute length of StringBuffer
+ int len = u.getProtocol().length() + 1;
+ if (u.getAuthority() != null && u.getAuthority().length() > 0)
+ len += 2 + u.getAuthority().length();
+ if (u.getPath() != null) {
+ len += u.getPath().length();
+ }
+ if (u.getQuery() != null) {
+ len += 1 + u.getQuery().length();
+ }
+ if (u.getRef() != null)
+ len += 1 + u.getRef().length();
+
+ StringBuffer result = new StringBuffer(len);
+ result.append(u.getProtocol());
+ result.append(":");
+ if (u.getAuthority() != null && u.getAuthority().length() > 0) {
+ result.append("//");
+ result.append(u.getAuthority());
+ }
+ if (u.getPath() != null) {
+ result.append(u.getPath());
+ }
+ if (u.getQuery() != null) {
+ result.append('?');
+ result.append(u.getQuery());
+ }
+ if (u.getRef() != null) {
+ result.append("#");
+ result.append(u.getRef());
+ }
+ return result.toString();
+ }
+
+ /**
+ * Sets the fields of the URL argument to the indicated values.
+ * Only classes derived from URLStreamHandler are supposed to be able
+ * to call the set method on a URL.
+ *
+ * @param u the URL to modify.
+ * @param protocol the protocol name.
+ * @param host the remote host value for the URL.
+ * @param port the port on the remote machine.
+ * @param authority the authority part for the URL.
+ * @param userInfo the userInfo part of the URL.
+ * @param path the path component of the URL.
+ * @param query the query part for the URL.
+ * @param ref the reference.
+ * @exception SecurityException if the protocol handler of the URL is
+ * different from this one
+ * @see java.net.URL#set(java.lang.String, java.lang.String, int, java.lang.String, java.lang.String)
+ * @since 1.3
+ */
+ protected void setURL(URL u, String protocol, String host, int port,
+ String authority, String userInfo, String path,
+ String query, String ref) {
+ if (this != u.handler) {
+ throw new SecurityException("handler for url different from " +
+ "this handler");
+ }
+ // ensure that no one can reset the protocol on a given URL.
+ u.set(u.getProtocol(), host, port, authority, userInfo, path, query, ref);
+ }
+
+ /**
+ * Sets the fields of the URL argument to the indicated values.
+ * Only classes derived from URLStreamHandler are supposed to be able
+ * to call the set method on a URL.
+ *
+ * @param u the URL to modify.
+ * @param protocol the protocol name. This value is ignored since 1.2.
+ * @param host the remote host value for the URL.
+ * @param port the port on the remote machine.
+ * @param file the file.
+ * @param ref the reference.
+ * @exception SecurityException if the protocol handler of the URL is
+ * different from this one
+ * @deprecated Use setURL(URL, String, String, int, String, String, String,
+ * String);
+ */
+ @Deprecated
+ protected void setURL(URL u, String protocol, String host, int port,
+ String file, String ref) {
+ /*
+ * Only old URL handlers call this, so assume that the host
+ * field might contain "user:passwd@host". Fix as necessary.
+ */
+ String authority = null;
+ String userInfo = null;
+ if (host != null && host.length() != 0) {
+ authority = (port == -1) ? host : host + ":" + port;
+ int at = host.lastIndexOf('@');
+ if (at != -1) {
+ userInfo = host.substring(0, at);
+ host = host.substring(at+1);
+ }
+ }
+
+ /*
+ * Assume file might contain query part. Fix as necessary.
+ */
+ String path = null;
+ String query = null;
+ if (file != null) {
+ int q = file.lastIndexOf('?');
+ if (q != -1) {
+ query = file.substring(q+1);
+ path = file.substring(0, q);
+ } else
+ path = file;
+ }
+ setURL(u, protocol, host, port, authority, userInfo, path, query, ref);
+ }
+}