* In general, a URL can be broken into several parts. Consider the * following example: *
** http://www.example.com/docs/resource1.html *
* The URL above indicates that the protocol to use is * {@code http} (HyperText Transfer Protocol) and that the * information resides on a host machine named * {@code www.example.com}. The information on that host * machine is named {@code /docs/resource1.html}. The exact * meaning of this name on the host machine is both protocol * dependent and host dependent. The information normally resides in * a file, but it could be generated on the fly. This component of * the URL is called the path component. *
* A URL can optionally specify a "port", which is the * port number to which the TCP connection is made on the remote host * machine. If the port is not specified, the default port for * the protocol is used instead. For example, the default port for * {@code http} is {@code 80}. An alternative port could be * specified as: *
** http://www.example.com:1080/docs/resource1.html *
* The syntax of {@code URL} is defined by RFC 2396: Uniform * Resource Identifiers (URI): Generic Syntax, amended by RFC 2732: Format for * Literal IPv6 Addresses in URLs. The Literal IPv6 address format * also supports scope_ids. The syntax and usage of scope_ids is described * here. *
* A URL may have appended to it a "fragment", also known * as a "ref" or a "reference". The fragment is indicated by the sharp * sign character "#" followed by more characters. For example, *
** http://java.sun.com/index.html#chapter1 *
* This fragment is not technically part of the URL. Rather, it * indicates that after the specified resource is retrieved, the * application is specifically interested in that part of the * document that has the tag {@code chapter1} attached to it. The * meaning of a tag is resource specific. *
* An application can also specify a "relative URL", * which contains only enough information to reach the resource * relative to another URL. Relative URLs are frequently used within * HTML pages. For example, if the contents of the URL: *
* contained within it the relative URL: ** http://java.sun.com/index.html *
* it would be a shorthand for: ** FAQ.html *
** http://java.sun.com/FAQ.html *
* The relative URL need not specify all the components of a URL. If * the protocol, host name, or port number is missing, the value is * inherited from the fully specified URL. The file component must be * specified. The optional fragment is not inherited. *
* The URL class does not itself encode or decode any URL components
* according to the escaping mechanism defined in RFC2396. It is the
* responsibility of the caller to encode any fields, which need to be
* escaped prior to calling URL, and also to decode any escaped fields,
* that are returned from URL. Furthermore, because URL has no knowledge
* of URL escaping, it does not recognise equivalence between the encoded
* or decoded form of the same URL. For example, the two URLs:
*
http://foo.com/hello world/ and http://foo.com/hello%20world* would be considered not equal to each other. *
* Note, the {@link java.net.URI} class does perform escaping of its * component fields in certain circumstances. The recommended way * to manage the encoding and decoding of URLs is to use {@link java.net.URI}, * and to convert between these two classes using {@link #toURI()} and * {@link URI#toURL()}. *
* The {@link URLEncoder} and {@link URLDecoder} classes can also be
* used, but only for HTML form encoding, which is not the same
* as the encoding scheme defined in RFC2396.
*
* @author James Gosling
* @since JDK1.0
*/
public final class URL implements java.io.Serializable {
static final String BUILTIN_HANDLERS_PREFIX = "sun.net.www.protocol";
static final long serialVersionUID = -7627629688361524110L;
/**
* The property which specifies the package prefix list to be scanned
* for protocol handlers. The value of this property (if any) should
* be a vertical bar delimited list of package names to search through
* for a protocol handler to load. The policy of this class is that
* all protocol handlers will be in a class called
* * {@code host} can be expressed as a host name or a literal * IP address. If IPv6 literal address is used, it should be * enclosed in square brackets ({@code '['} and {@code ']'}), as * specified by RFC 2732; * However, the literal IPv6 address format defined in RFC 2373: IP * Version 6 Addressing Architecture is also accepted.
* * Specifying a {@code port} number of {@code -1} * indicates that the URL should use the default port for the * protocol.
* * If this is the first URL object being created with the specified * protocol, a stream protocol handler object, an instance of * class {@code URLStreamHandler}, is created for that protocol: *
* java.protocol.handler.pkgs
* * <package>.<protocol>.Handler
* * <system default package>.<protocol>.Handler
* Protocol handlers for the following protocols are guaranteed * to exist on the search path :- *
* http, https, file, and jar
* No validation of the inputs is performed by this constructor. * * @param protocol the name of the protocol to use. * @param host the name of the host. * @param port the port number on the host. * @param file the file on the host * @exception MalformedURLException if an unknown protocol is specified. * @see java.lang.System#getProperty(java.lang.String) * @see java.net.URL#setURLStreamHandlerFactory( * java.net.URLStreamHandlerFactory) * @see java.net.URLStreamHandler * @see java.net.URLStreamHandlerFactory#createURLStreamHandler( * java.lang.String) */ public URL(String protocol, String host, int port, String file) throws MalformedURLException { this(protocol, host, port, file, null); } /** * Creates a URL from the specified {@code protocol} * name, {@code host} name, and {@code file} name. The * default port for the specified protocol is used. *
* This method is equivalent to calling the four-argument * constructor with the arguments being {@code protocol}, * {@code host}, {@code -1}, and {@code file}. * * No validation of the inputs is performed by this constructor. * * @param protocol the name of the protocol to use. * @param host the name of the host. * @param file the file on the host. * @exception MalformedURLException if an unknown protocol is specified. * @see java.net.URL#URL(java.lang.String, java.lang.String, * int, java.lang.String) */ public URL(String protocol, String host, String file) throws MalformedURLException { this(protocol, host, -1, file); } /** * Creates a {@code URL} object from the specified * {@code protocol}, {@code host}, {@code port} * number, {@code file}, and {@code handler}. Specifying * a {@code port} number of {@code -1} indicates that * the URL should use the default port for the protocol. Specifying * a {@code handler} of {@code null} indicates that the URL * should use a default stream handler for the protocol, as outlined * for: * java.net.URL#URL(java.lang.String, java.lang.String, int, * java.lang.String) * *
If the handler is not null and there is a security manager, * the security manager's {@code checkPermission} * method is called with a * {@code NetPermission("specifyStreamHandler")} permission. * This may result in a SecurityException. * * No validation of the inputs is performed by this constructor. * * @param protocol the name of the protocol to use. * @param host the name of the host. * @param port the port number on the host. * @param file the file on the host * @param handler the stream handler for the URL. * @exception MalformedURLException if an unknown protocol is specified. * @exception SecurityException * if a security manager exists and its * {@code checkPermission} method doesn't allow * specifying a stream handler explicitly. * @see java.lang.System#getProperty(java.lang.String) * @see java.net.URL#setURLStreamHandlerFactory( * java.net.URLStreamHandlerFactory) * @see java.net.URLStreamHandler * @see java.net.URLStreamHandlerFactory#createURLStreamHandler( * java.lang.String) * @see SecurityManager#checkPermission * @see java.net.NetPermission */ public URL(String protocol, String host, int port, String file, URLStreamHandler handler) throws MalformedURLException { if (handler != null) { SecurityManager sm = System.getSecurityManager(); if (sm != null) { // check for permission to specify a handler checkSpecifyHandler(sm); } } protocol = protocol.toLowerCase(); this.protocol = protocol; if (host != null) { /** * if host is a literal IPv6 address, * we will make it conform to RFC 2732 */ if (host.indexOf(':') >= 0 && !host.startsWith("[")) { host = "["+host+"]"; } this.host = host; if (port < -1) { throw new MalformedURLException("Invalid port number :" + port); } this.port = port; authority = (port == -1) ? host : host + ":" + port; } Parts parts = new Parts(file); path = parts.getPath(); query = parts.getQuery(); if (query != null) { this.file = path + "?" + query; } else { this.file = path; } ref = parts.getRef(); // Note: we don't do validation of the URL here. Too risky to change // right now, but worth considering for future reference. -br if (handler == null && (handler = getURLStreamHandler(protocol)) == null) { throw new MalformedURLException("unknown protocol: " + protocol); } this.handler = handler; } /** * Creates a {@code URL} object from the {@code String} * representation. *
* This constructor is equivalent to a call to the two-argument * constructor with a {@code null} first argument. * * @param spec the {@code String} to parse as a URL. * @exception MalformedURLException if no protocol is specified, or an * unknown protocol is found, or {@code spec} is {@code null}. * @see java.net.URL#URL(java.net.URL, java.lang.String) */ public URL(String spec) throws MalformedURLException { this(null, spec); } /** * Creates a URL by parsing the given spec within a specified context. * * The new URL is created from the given context URL and the spec * argument as described in * RFC2396 "Uniform Resource Identifiers : Generic * Syntax" : *
* <scheme>://<authority><path>?<query>#<fragment>
* * If the scheme component is defined in the given spec and does not match * the scheme of the context, then the new URL is created as an absolute * URL based on the spec alone. Otherwise the scheme component is inherited * from the context URL. *
* If the authority component is present in the spec then the spec is * treated as absolute and the spec authority and path will replace the * context authority and path. If the authority component is absent in the * spec then the authority of the new URL will be inherited from the * context. *
* If the spec's path component begins with a slash character * "/" then the * path is treated as absolute and the spec path replaces the context path. *
* Otherwise, the path is treated as a relative path and is appended to the * context path, as described in RFC2396. Also, in this case, * the path is canonicalized through the removal of directory * changes made by occurrences of ".." and ".". *
* For a more detailed description of URL parsing, refer to RFC2396.
*
* @param context the context in which to parse the specification.
* @param spec the {@code String} to parse as a URL.
* @exception MalformedURLException if no protocol is specified, or an
* unknown protocol is found, or {@code spec} is {@code null}.
* @see java.net.URL#URL(java.lang.String, java.lang.String,
* int, java.lang.String)
* @see java.net.URLStreamHandler
* @see java.net.URLStreamHandler#parseURL(java.net.URL,
* java.lang.String, int, int)
*/
public URL(URL context, String spec) throws MalformedURLException {
this(context, spec, null);
}
/**
* Creates a URL by parsing the given spec with the specified handler
* within a specified context. If the handler is null, the parsing
* occurs as with the two argument constructor.
*
* @param context the context in which to parse the specification.
* @param spec the {@code String} to parse as a URL.
* @param handler the stream handler for the URL.
* @exception MalformedURLException if no protocol is specified, or an
* unknown protocol is found, or {@code spec} is {@code null}.
* @exception SecurityException
* if a security manager exists and its
* {@code checkPermission} method doesn't allow
* specifying a stream handler.
* @see java.net.URL#URL(java.lang.String, java.lang.String,
* int, java.lang.String)
* @see java.net.URLStreamHandler
* @see java.net.URLStreamHandler#parseURL(java.net.URL,
* java.lang.String, int, int)
*/
public URL(URL context, String spec, URLStreamHandler handler)
throws MalformedURLException
{
String original = spec;
int i, limit, c;
int start = 0;
String newProtocol = null;
boolean aRef=false;
boolean isRelative = false;
// Check for permission to specify a handler
if (handler != null) {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkSpecifyHandler(sm);
}
}
try {
limit = spec.length();
while ((limit > 0) && (spec.charAt(limit - 1) <= ' ')) {
limit--; //eliminate trailing whitespace
}
while ((start < limit) && (spec.charAt(start) <= ' ')) {
start++; // eliminate leading whitespace
}
if (spec.regionMatches(true, start, "url:", 0, 4)) {
start += 4;
}
if (start < spec.length() && spec.charAt(start) == '#') {
/* we're assuming this is a ref relative to the context URL.
* This means protocols cannot start w/ '#', but we must parse
* ref URL's like: "hello:there" w/ a ':' in them.
*/
aRef=true;
}
for (i = start ; !aRef && (i < limit) &&
((c = spec.charAt(i)) != '/') ; i++) {
if (c == ':') {
String s = spec.substring(start, i).toLowerCase();
if (isValidProtocol(s)) {
newProtocol = s;
start = i + 1;
}
break;
}
}
// Only use our context if the protocols match.
protocol = newProtocol;
if ((context != null) && ((newProtocol == null) ||
newProtocol.equalsIgnoreCase(context.protocol))) {
// inherit the protocol handler from the context
// if not specified to the constructor
if (handler == null) {
handler = context.handler;
}
// If the context is a hierarchical URL scheme and the spec
// contains a matching scheme then maintain backwards
// compatibility and treat it as if the spec didn't contain
// the scheme; see 5.2.3 of RFC2396
if (context.path != null && context.path.startsWith("/"))
newProtocol = null;
if (newProtocol == null) {
protocol = context.protocol;
authority = context.authority;
userInfo = context.userInfo;
host = context.host;
port = context.port;
file = context.file;
path = context.path;
isRelative = true;
}
}
if (protocol == null) {
throw new MalformedURLException("no protocol: "+original);
}
// Get the protocol handler if not specified or the protocol
// of the context could not be used
if (handler == null &&
(handler = getURLStreamHandler(protocol)) == null) {
throw new MalformedURLException("unknown protocol: "+protocol);
}
this.handler = handler;
i = spec.indexOf('#', start);
if (i >= 0) {
ref = spec.substring(i + 1, limit);
limit = i;
}
/*
* Handle special case inheritance of query and fragment
* implied by RFC2396 section 5.2.2.
*/
if (isRelative && start == limit) {
query = context.query;
if (ref == null) {
ref = context.ref;
}
}
handler.parseURL(this, spec, start, limit);
} catch(MalformedURLException e) {
throw e;
} catch(Exception e) {
MalformedURLException exception = new MalformedURLException(e.getMessage());
exception.initCause(e);
throw exception;
}
}
/*
* Returns true if specified string is a valid protocol name.
*/
private boolean isValidProtocol(String protocol) {
int len = protocol.length();
if (len < 1)
return false;
char c = protocol.charAt(0);
if (!Character.isLetter(c))
return false;
for (int i = 1; i < len; i++) {
c = protocol.charAt(i);
if (!Character.isLetterOrDigit(c) && c != '.' && c != '+' &&
c != '-') {
return false;
}
}
return true;
}
/*
* Checks for permission to specify a stream handler.
*/
private void checkSpecifyHandler(SecurityManager sm) {
sm.checkPermission(SecurityConstants.SPECIFY_HANDLER_PERMISSION);
}
/**
* Sets the fields of the URL. This is not a public method so that
* only URLStreamHandlers can modify URL fields. URLs are
* otherwise constant.
*
* @param protocol the name of the protocol to use
* @param host the name of the host
@param port the port number on the host
* @param file the file on the host
* @param ref the internal reference in the URL
*/
void set(String protocol, String host, int port,
String file, String ref) {
synchronized (this) {
this.protocol = protocol;
this.host = host;
authority = port == -1 ? host : host + ":" + port;
this.port = port;
this.file = file;
this.ref = ref;
/* This is very important. We must recompute this after the
* URL has been changed. */
hashCode = -1;
hostAddress = null;
int q = file.lastIndexOf('?');
if (q != -1) {
query = file.substring(q+1);
path = file.substring(0, q);
} else
path = file;
}
}
/**
* Sets the specified 8 fields of the URL. This is not a public method so
* that only URLStreamHandlers can modify URL fields. URLs are otherwise
* constant.
*
* @param protocol the name of the protocol to use
* @param host the name of the host
* @param port the port number on the host
* @param authority the authority part for the url
* @param userInfo the username and password
* @param path the file on the host
* @param ref the internal reference in the URL
* @param query the query part of this URL
* @since 1.3
*/
void set(String protocol, String host, int port,
String authority, String userInfo, String path,
String query, String ref) {
synchronized (this) {
this.protocol = protocol;
this.host = host;
this.port = port;
this.file = query == null ? path : path + "?" + query;
this.userInfo = userInfo;
this.path = path;
this.ref = ref;
/* This is very important. We must recompute this after the
* URL has been changed. */
hashCode = -1;
hostAddress = null;
this.query = query;
this.authority = authority;
}
}
/**
* Gets the query part of this {@code URL}.
*
* @return the query part of this {@code URL},
* or null if one does not exist
* @since 1.3
*/
public String getQuery() {
return query;
}
/**
* Gets the path part of this {@code URL}.
*
* @return the path part of this {@code URL}, or an
* empty string if one does not exist
* @since 1.3
*/
public String getPath() {
return path;
}
/**
* Gets the userInfo part of this {@code URL}.
*
* @return the userInfo part of this {@code URL}, or
* null if one does not exist
* @since 1.3
*/
public String getUserInfo() {
return userInfo;
}
/**
* Gets the authority part of this {@code URL}.
*
* @return the authority part of this {@code URL}
* @since 1.3
*/
public String getAuthority() {
return authority;
}
/**
* Gets the port number of this {@code URL}.
*
* @return the port number, or -1 if the port is not set
*/
public int getPort() {
return port;
}
/**
* Gets the default port number of the protocol associated
* with this {@code URL}. If the URL scheme or the URLStreamHandler
* for the URL do not define a default port number,
* then -1 is returned.
*
* @return the port number
* @since 1.4
*/
public int getDefaultPort() {
return handler.getDefaultPort();
}
/**
* Gets the protocol name of this {@code URL}.
*
* @return the protocol of this {@code URL}.
*/
public String getProtocol() {
return protocol;
}
/**
* Gets the host name of this {@code URL}, if applicable.
* The format of the host conforms to RFC 2732, i.e. for a
* literal IPv6 address, this method will return the IPv6 address
* enclosed in square brackets ({@code '['} and {@code ']'}).
*
* @return the host name of this {@code URL}.
*/
public String getHost() {
return host;
}
/**
* Gets the file name of this {@code URL}.
* The returned file portion will be
* the same as getPath(), plus the concatenation of
* the value of getQuery(), if any. If there is
* no query portion, this method and getPath() will
* return identical results.
*
* @return the file name of this {@code URL},
* or an empty string if one does not exist
*/
public String getFile() {
return file;
}
/**
* Gets the anchor (also known as the "reference") of this
* {@code URL}.
*
* @return the anchor (also known as the "reference") of this
* {@code URL}, or null if one does not exist
*/
public String getRef() {
return ref;
}
/**
* Compares this URL for equality with another object.
* * If the given object is not a URL then this method immediately returns * {@code false}.
* * Two URL objects are equal if they have the same protocol, reference * equivalent hosts, have the same port number on the host, and the same * file and fragment of the file.
* * Two hosts are considered equivalent if both host names can be resolved * into the same IP addresses; else if either host name can't be * resolved, the host names must be equal without regard to case; or both * host names equal to null.
* * Since hosts comparison requires name resolution, this operation is a * blocking operation.
* * Note: The defined behavior for {@code equals} is known to * be inconsistent with virtual hosting in HTTP. * * @param obj the URL to compare against. * @return {@code true} if the objects are the same; * {@code false} otherwise. */ public boolean equals(Object obj) { if (!(obj instanceof URL)) return false; URL u2 = (URL)obj; return handler.equals(this, u2); } /** * Creates an integer suitable for hash table indexing.
* * The hash code is based upon all the URL components relevant for URL * comparison. As such, this operation is a blocking operation.
* * @return a hash code for this {@code URL}. */ public synchronized int hashCode() { if (hashCode != -1) return hashCode; hashCode = handler.hashCode(this); return hashCode; } /** * Compares two URLs, excluding the fragment component.
* * Returns {@code true} if this {@code URL} and the * {@code other} argument are equal without taking the * fragment component into consideration. * * @param other the {@code URL} to compare against. * @return {@code true} if they reference the same remote object; * {@code false} otherwise. */ public boolean sameFile(URL other) { return handler.sameFile(this, other); } /** * Constructs a string representation of this {@code URL}. The * string is created by calling the {@code toExternalForm} * method of the stream protocol handler for this object. * * @return a string representation of this object. * @see java.net.URL#URL(java.lang.String, java.lang.String, int, * java.lang.String) * @see java.net.URLStreamHandler#toExternalForm(java.net.URL) */ public String toString() { return toExternalForm(); } /** * Constructs a string representation of this {@code URL}. The * string is created by calling the {@code toExternalForm} * method of the stream protocol handler for this object. * * @return a string representation of this object. * @see java.net.URL#URL(java.lang.String, java.lang.String, * int, java.lang.String) * @see java.net.URLStreamHandler#toExternalForm(java.net.URL) */ public String toExternalForm() { return handler.toExternalForm(this); } /** * Returns a {@link java.net.URI} equivalent to this URL. * This method functions in the same way as {@code new URI (this.toString())}. *
Note, any URL instance that complies with RFC 2396 can be converted * to a URI. However, some URLs that are not strictly in compliance * can not be converted to a URI. * * @exception URISyntaxException if this URL is not formatted strictly according to * to RFC2396 and cannot be converted to a URI. * * @return a URI instance equivalent to this URL. * @since 1.5 */ public URI toURI() throws URISyntaxException { return new URI (toString()); } /** * Returns a {@link java.net.URLConnection URLConnection} instance that * represents a connection to the remote object referred to by the * {@code URL}. * *
A new instance of {@linkplain java.net.URLConnection URLConnection} is * created every time when invoking the * {@linkplain java.net.URLStreamHandler#openConnection(URL) * URLStreamHandler.openConnection(URL)} method of the protocol handler for * this URL.
* *It should be noted that a URLConnection instance does not establish * the actual network connection on creation. This will happen only when * calling {@linkplain java.net.URLConnection#connect() URLConnection.connect()}.
* *If for the URL'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.
* * @return a {@link java.net.URLConnection URLConnection} linking * to the URL. * @exception IOException if an I/O exception occurs. * @see java.net.URL#URL(java.lang.String, java.lang.String, * int, java.lang.String) */ public URLConnection openConnection() throws java.io.IOException { return handler.openConnection(this); } /** * Same as {@link #openConnection()}, except that the connection will be * made through the specified proxy; Protocol handlers that do not * support proxing will ignore the proxy parameter and make a * normal connection. * * Invoking this method preempts the system's default ProxySelector * settings. * * @param proxy the Proxy through which this connection * will be made. If direct connection is desired, * Proxy.NO_PROXY should be specified. * @return a {@code URLConnection} to the URL. * @exception IOException if an I/O exception occurs. * @exception SecurityException if a security manager is present * and the caller doesn't have permission to connect * to the proxy. * @exception IllegalArgumentException will be thrown if proxy is null, * or proxy has the wrong type * @exception UnsupportedOperationException if the subclass that * implements the protocol handler doesn't support * this method. * @see java.net.URL#URL(java.lang.String, java.lang.String, * int, java.lang.String) * @see java.net.URLConnection * @see java.net.URLStreamHandler#openConnection(java.net.URL, * java.net.Proxy) * @since 1.5 */ public URLConnection openConnection(Proxy proxy) throws java.io.IOException { if (proxy == null) { throw new IllegalArgumentException("proxy can not be null"); } // Create a copy of Proxy as a security measure Proxy p = proxy == Proxy.NO_PROXY ? Proxy.NO_PROXY : sun.net.ApplicationProxy.create(proxy); SecurityManager sm = System.getSecurityManager(); if (p.type() != Proxy.Type.DIRECT && sm != null) { InetSocketAddress epoint = (InetSocketAddress) p.address(); if (epoint.isUnresolved()) sm.checkConnect(epoint.getHostName(), epoint.getPort()); else sm.checkConnect(epoint.getAddress().getHostAddress(), epoint.getPort()); } return handler.openConnection(this, p); } /** * Opens a connection to this {@code URL} and returns an * {@code InputStream} for reading from that connection. This * method is a shorthand for: * * openConnection().getInputStream()
* * openConnection().getContent()
* * openConnection().getContent(Class[])
* The {@code URLStreamHandlerFactory} instance is used to *construct a stream protocol handler from a protocol name. * *
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 fac the desired factory.
* @exception Error if the application has already set a factory.
* @exception SecurityException if a security manager exists and its
* {@code checkSetFactory} method doesn't allow
* the operation.
* @see java.net.URL#URL(java.lang.String, java.lang.String,
* int, java.lang.String)
* @see java.net.URLStreamHandlerFactory
* @see SecurityManager#checkSetFactory
*/
public static void setURLStreamHandlerFactory(URLStreamHandlerFactory fac) {
synchronized (streamHandlerLock) {
if (factory != null) {
throw new Error("factory already defined");
}
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkSetFactory();
}
handlers.clear();
factory = fac;
}
}
/**
* A table of protocol handlers.
*/
static Hashtable