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1. Examples of GoF Design Patterns
I am learning GoF Java Design Patterns and I want to see some real life examples of them. Can you guys point to some good usage of these Design Patterns.(preferably in Java's core libraries). Thank you
2. How to use java.net.URLConnection to fire and handle HTTP requests?
This subject is pretty often asked here and the Sun Oracle tutorial is too concise about the subject. So I thought, let's post a CW question and answer about this so that it can if necessary be referenced in other topics. Others are of course free to add more hints and best practices here.
3. Parsing query strings in Java
J2EE has ServletRequest.getParameterValues(). On non-EE platforms, URL.getQuery() simply returns a string. What's the normal way to properly parse the query string in a URL when not on J2EE? <rant> It is popular in the answers to try and make your own parser. This is very interesting and exciting micro-coding project, but I cannot say that it is a good idea :( The code snippets ...
4. How do you Programmatically Download a Webpage in Java
I would like to be able to fetch a web page's html and save it to a String, so I can do some processing on it. Also, how could I handle various types of compression. How would I go about doing that using Java?
5. Is there a good url builder for Java?
Is there a good url builder for java?
6. Validating URL in Java
I wanted to know if there is any standard APIs in Java to validate a given URL? I want to check both if the URL string is right i.e. the given protocol is valid and then to check if a connection can be established. I tried using HttpURLConnection, providing the URL and connecting to it. The first part of my requirement seems to be fulfilled but when I try to perform HttpURLConnection.connect(...
7. Is Java incomplete?
Why do I always feel that Java never worried about growing its own API (the one that comes with it)? I've got several examples.. File upload. Servlet API does not handle it. Easy XML reading Connection pooling HttpClient support Good logging Encoders And so goes on... several lacks that we have to look for third party APIs and its requirements and etc. Why? I came from C#, and I am ...
8. How can you search Google Programmatically Java API
Does anyone know if and how it is possible to search Google programmatically - especially if there is a Java API for it. Thanks in advance. Daniel
9. Java: how to get a File from an escaped URL?
I'm receiving an URL that locates a local file (the fact that I receive an URL is not in my control). The URL is escaped validly as defined in RFC2396. How can I transform this to a Java File object? Funnily enough, the URL getFile() method returns a String, not a File. I've created a directory called "/tmp/some dir" (with a spacing character between "some" and "dir"), which is correctly lo...
10. Standard Java Class for common URL/URI maniupulation
This question has almost certainly been asked before, but I ask it anyway because I couldn't find an answer. Generally, is there a utility class of some sort that assists in common String manipulations associated with URL/URIs? I'm thinking something like Java SE's URL Class, but maybe a little beefier. I'm looking for something that will let you do simple things, like: Get a List of query...
11. How to detect the presence of URL in a string
I have an input String say Please go to http://stackoverflow.com. The url part of the String is detected and an anchor <a href=""></a> is automatically added by many browser/IDE/applications. So it becomes Please go to <a href='http://stackoverflow.com'>http://stackoverflow.com</a>. I need to do the same using Java.
12. URL valid characters. java to validate
a string like: 'www.test.com' is good. a string like: 'www.888.com' is good. a string like: 'stackoverflow.com' is good. a string like: 'GOoGle.Com' is good. why ? because those are valid urls. it does not necessarely matter if they have been registered or not. now bad strings are: 'goog*d\x' 'manydots...com' why because you can't register those urls. if I have a string in java whi...
13. How do I do a HTTP GET in Java?
How do I do a HTTP GET in Java? Thanks. David
14. What is the quickest way to detect an unreachable host in Java?
I would like the fastest and most accurate function boolean isReachable(String host, int port) that passes the following JUnit tests under the conditions below. Timeout values are specified by the JUnit test itself, and may be considered "unreachable." Please note: All answers must be platform-independent. This means that InetAddress.isReachable(int timeout) is not going to work, since it reli...
15. How do I retrieve a URL from a web site using Java?
I want to use HTTP GET and POST commands to retrieve URLs from a website and parse the HTML. How do I do this?
16. Why does my applet get a java.security.AccessControlException: access denied (java.net.SocketPermission ...), and how can I a...
We are clueless about why my client is encountering a Java Security exception in Safari. Could anyone help? The exception occurs reliably in Safari on Windows. This involves a Java applet. The exception also occurs with Firefox and IE8 on Windows Vista. Here are the steps to reproduce: Open Safari on Windows Click here: http://www.cengraving.com/s/item?itemId=CH003 Click "Customize" (at ...
17. What is in Java the 'system default package'?
While researching the URLConnection class I stumbled on a reference to system default package in the API docs for the URL class here. Anyone knows what that is? Thanks.
18. GWT replacement for java.net.URL
I have to replace the protocol part of a already existing url in GWT. The java.net package has a class which was build for exactly that purpose: URL. Sadly GWT does not emulate the java.net package. How can I reassemble a url in GWT without creating my own parser? (I know about UrlBuilder, but UrlBuilder won't take an existing URL) Example: I have a url in a string "http://myserver.com/somepa...
19. Java can't find file when running through Eclipse
When I run a Java application that should be reading from a file in Eclipse, I get a java.io.FileNotFoundException, even though the file is in the correct directory. I can compile and run the application from the command line just fine; the problem only occurs in Eclipse, with more than one project and application. Is there a setting I need to change in the run configurations or build paths t...
20. Could you share a link to an URL parsing implementation?
As far as I understand, an URL consists of the folowing fields: Protocol (http, https, ftp, etc.) User name User Password Host address (an IP address or a DNS FQDN) Port (which can be implied) Path to a document inside the server documents root Set of arguments and values Document part (#) as protocol://user:password@host:port/path/document?arg1=val1&arg2=val2#part I need a code to get va...
21. Java: Load a resource contained in a jar
In my application I load resources in this manner: WinProcessor.class.getResource("repository").toString(); and this gives me: file:/root/app/repository (and I replace "file:" with empty string) This works fine when I run my application from the IDE, but when I run the jar of my application: java -jar app.jar The path becomes: jar:/root/app.jar!/repository is there any way to solv... 
1
   /*
2
    * Copyright 1995-2007 Sun Microsystems, Inc.  All Rights Reserved.
3
    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4
    *
5
    * This code is free software; you can redistribute it and/or modify it
6
    * under the terms of the GNU General Public License version 2 only, as
7
    * published by the Free Software Foundation.  Sun designates this
8
    * particular file as subject to the "Classpath" exception as provided
9
    * by Sun in the LICENSE file that accompanied this code.
10
   *
11
   * This code is distributed in the hope that it will be useful, but WITHOUT
12
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14
   * version 2 for more details (a copy is included in the LICENSE file that
15
   * accompanied this code).
16
   *
17
   * You should have received a copy of the GNU General Public License version
18
   * 2 along with this work; if not, write to the Free Software Foundation,
19
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20
   *
21
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22
   * CA 95054 USA or visit www.sun.com if you need additional information or
23
   * have any questions.
24
   */
25
  
26
  package java.net;
27
  
Class URL represents a Uniform Resource Locator, a pointer to a "resource" on the World Wide Web. A resource can be something as simple as a file or a directory, or it can be a reference to a more complicated object, such as a query to a database or to a search engine. More information on the types of URLs and their formats can be found at:
http://www.socs.uts.edu.au/MosaicDocs-old/url-primer.html

In general, a URL can be broken into several parts. The previous example of a URL indicates that the protocol to use is http (HyperText Transfer Protocol) and that the information resides on a host machine named www.socs.uts.edu.au. The information on that host machine is named /MosaicDocs-old/url-primer.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 http is 80. An alternative port could be specified as: 

     http://www.socs.uts.edu.au:80/MosaicDocs-old/url-primer.html

The syntax of 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 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: 

     http://java.sun.com/index.html
contained within it the relative URL: 
     FAQ.html
it would be a shorthand for: 
     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 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 URI, and to convert between these two classes using toURI() and URI.toURL().

The URLEncoder and 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(s):
James Gosling
Since:
JDK1.0
132
 
133
 public final class URL implements java.io.Serializable {
134
 
135
     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 <protocolname>.Handler, and each package in the list is examined in turn for a matching handler. If none are found (or the property is not specified), the default package prefix, sun.net.www.protocol, is used. The search proceeds from the first package in the list to the last and stops when a match is found. 
148
 
149
     private static final String protocolPathProp = "java.protocol.handler.pkgs";

    
The protocol to use (ftp, http, nntp, ... etc.) .

Serial:
154
 
155
     private String protocol;

    
The host name to connect to.

Serial:
160
 
161
     private String host;

    
The protocol port to connect to.

Serial:
166
 
167
     private int port = -1;

    
The specified file name on that host. file is defined as path[?query]

Serial:
173
 
174
     private String file;

    
The query part of this URL. 
178
 
179
     private transient String query;

    
The authority part of this URL.

Serial:
184
 
185
     private String authority;

    
The path part of this URL. 
189
 
190
     private transient String path;

    
The userinfo part of this URL. 
194
 
195
     private transient String userInfo;

    
# reference.

Serial:
200
 
201
     private String ref;

    
The host's IP address, used in equals and hashCode. Computed on demand. An uninitialized or unknown hostAddress is null. 
206
 
207
     transient InetAddress hostAddress;

    
The URLStreamHandler for this URL. 
211
 
212
     transient URLStreamHandler handler;
213
 
214
     /* Our hash code.
215
      * @serial
216
      */
217
     private int hashCode = -1;

    
Creates a URL object from the specified protocol, host, port number, and file.

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 ('[' and ']'), 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 port number of -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 URLStreamHandler, is created for that protocol:

  1. If the application has previously set up an instance of URLStreamHandlerFactory as the stream handler factory, then the createURLStreamHandler method of that instance is called with the protocol string as an argument to create the stream protocol handler.
  2. If no URLStreamHandlerFactory has yet been set up, or if the factory's createURLStreamHandler method returns null, then the constructor finds the value of the system property: 
             java.protocol.handler.pkgs
    If the value of that system property is not null, it is interpreted as a list of packages separated by a vertical slash character '|'. The constructor tries to load the class named: 
             <package>.<protocol>.Handler
    where <package> is replaced by the name of the package and <protocol> is replaced by the name of the protocol. If this class does not exist, or if the class exists but it is not a subclass of URLStreamHandler, then the next package in the list is tried.
  3. If the previous step fails to find a protocol handler, then the constructor tries to load from a system default package. 
             <system default package>.<protocol>.Handler
    If this class does not exist, or if the class exists but it is not a subclass of URLStreamHandler, then a MalformedURLException is thrown.

Protocol handlers for the following protocols are guaranteed to exist on the search path :- 

     http, https, ftp, file, and jar
Protocol handlers for additional protocols may also be available.

No validation of the inputs is performed by this constructor.

Parameters:
protocol the name of the protocol to use.
host the name of the host.
port the port number on the host.
file the file on the host
Throws:
MalformedURLException if an unknown protocol is specified.
See also:
java.lang.System.getProperty(java.lang.String)
setURLStreamHandlerFactory(java.net.URLStreamHandlerFactory)
URLStreamHandler
URLStreamHandlerFactory.createURLStreamHandler(java.lang.String)
296
 
297
     public URL(String protocol, String host, int port, String file)
298
         throws MalformedURLException
299
     {
300
         this(protocol, host, port, file, null);
301
     }

    
Creates a URL from the specified protocol name, host name, and 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 protocol, host, -1, and file. No validation of the inputs is performed by this constructor.

Parameters:
protocol the name of the protocol to use.
host the name of the host.
file the file on the host.
Throws:
MalformedURLException if an unknown protocol is specified.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
320
 
321
     public URL(String protocol, String host, String file)
322
             throws MalformedURLException {
323
         this(protocol, host, -1, file);
324
     }

    
Creates a URL object from the specified protocol, host, port number, file, and handler. Specifying a port number of -1 indicates that the URL should use the default port for the protocol. Specifying a handler of 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 checkPermission method is called with a NetPermission("specifyStreamHandler") permission. This may result in a SecurityException. No validation of the inputs is performed by this constructor.

Parameters:
protocol the name of the protocol to use.
host the name of the host.
port the port number on the host.
file the file on the host
handler the stream handler for the URL.
Throws:
MalformedURLException if an unknown protocol is specified.
java.lang.SecurityException if a security manager exists and its checkPermission method doesn't allow specifying a stream handler explicitly.
See also:
java.lang.System.getProperty(java.lang.String)
setURLStreamHandlerFactory(java.net.URLStreamHandlerFactory)
URLStreamHandler
URLStreamHandlerFactory.createURLStreamHandler(java.lang.String)
java.lang.SecurityManager.checkPermission(java.security.Permission)
NetPermission
364
 
365
     public URL(String protocol, String host, int port, String file,
366
                URLStreamHandler handler) throws MalformedURLException {
367
         if (handler != null) {
368
             SecurityManager sm = System.getSecurityManager();
369
             if (sm != null) {
370
                 // check for permission to specify a handler
371
                 checkSpecifyHandler(sm);
372
             }
373
         }
374
 
375
         protocol = protocol.toLowerCase();
376
         this. = protocol;
377
         if (host != null) {

            
if host is a literal IPv6 address, we will make it conform to RFC 2732 
382
 
383
             if (host.indexOf(':') >= 0 && !host.startsWith("[")) {
384
                 host = "["+host+"]";
385
             }
386
             this. = host;
387
 
388
             if (port < -1) {
389
                 throw new MalformedURLException("Invalid port number :" +
390
                                                     port);
391
             }
392
             this. = port;
393
              = (port == -1) ? host : host + ":" + port;
394
         }
395
 
396
         Parts parts = new Parts(file);
397
          = parts.getPath();
398
          = parts.getQuery();
399
 
400
         if ( != null) {
401
             this. =  + "?" + ;
402
         } else {
403
             this. = ;
404
         }
405
          = parts.getRef();
406
 
407
         // Note: we don't do validation of the URL here. Too risky to change
408
         // right now, but worth considering for future reference. -br
409
         if (handler == null &&
410
             (handler = getURLStreamHandler(protocol)) == null) {
411
             throw new MalformedURLException("unknown protocol: " + protocol);
412
         }
413
         this. = handler;
414
     }

    
Creates a URL object from the String representation.

This constructor is equivalent to a call to the two-argument constructor with a null first argument.

Parameters:
spec the String to parse as a URL.
Throws:
MalformedURLException If the string specifies an unknown protocol.
See also:
java.net.URL.URL(java.net.URL,java.lang.String)
427
 
428
     public URL(String spec) throws MalformedURLException {
429
         this(null, spec);
430
     }

    
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>
The reference is parsed into the scheme, authority, path, query and fragment parts. If the path component is empty and the scheme, authority, and query components are undefined, then the new URL is a reference to the current document. Otherwise, the fragment and query parts present in the spec are used in the new URL.

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 occurences of ".." and ".".

For a more detailed description of URL parsing, refer to RFC2396.

Parameters:
context the context in which to parse the specification.
spec the String to parse as a URL.
Throws:
MalformedURLException if no protocol is specified, or an unknown protocol is found.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLStreamHandler
URLStreamHandler.parseURL(java.net.URL,java.lang.String,int,int)
478
 
479
     public URL(URL context, String spec) throws MalformedURLException {
480
         this(context, spec, null);
481
     }

    
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.

Parameters:
context the context in which to parse the specification.
spec the String to parse as a URL.
handler the stream handler for the URL.
Throws:
MalformedURLException if no protocol is specified, or an unknown protocol is found.
java.lang.SecurityException if a security manager exists and its checkPermission method doesn't allow specifying a stream handler.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLStreamHandler
URLStreamHandler.parseURL(java.net.URL,java.lang.String,int,int)
502
 
503
     public URL(URL context, String spec, URLStreamHandler handler)
504
         throws MalformedURLException
505
     {
506
         String original = spec;
507
         int i, limit, c;
508
         int start = 0;
509
         String newProtocol = null;
510
         boolean aRef=false;
511
         boolean isRelative = false;
512
 
513
         // Check for permission to specify a handler
514
         if (handler != null) {
515
             SecurityManager sm = System.getSecurityManager();
516
             if (sm != null) {
517
                 checkSpecifyHandler(sm);
518
             }
519
         }
520
 
521
         try {
522
             limit = spec.length();
523
             while ((limit > 0) && (spec.charAt(limit - 1) <= ' ')) {
524
                 limit--;        //eliminate trailing whitespace
525
             }
526
             while ((start < limit) && (spec.charAt(start) <= ' ')) {
527
                 start++;        // eliminate leading whitespace
528
             }
529
 
530
             if (spec.regionMatches(true, start, "url:", 0, 4)) {
531
                 start += 4;
532
             }
533
             if (start < spec.length() && spec.charAt(start) == '#') {
534
                 /* we're assuming this is a ref relative to the context URL.
535
                  * This means protocols cannot start w/ '#', but we must parse
536
                  * ref URL's like: "hello:there" w/ a ':' in them.
537
                  */
538
                 aRef=true;
539
             }
540
             for (i = start ; !aRef && (i < limit) &&
541
                      ((c = spec.charAt(i)) != '/') ; i++) {
542
                 if (c == ':') {
543
 
544
                     String s = spec.substring(start, i).toLowerCase();
545
                     if (isValidProtocol(s)) {
546
                         newProtocol = s;
547
                         start = i + 1;
548
                     }
549
                     break;
550
                 }
551
             }
552
 
553
             // Only use our context if the protocols match.
554
              = newProtocol;
555
             if ((context != null) && ((newProtocol == null) ||
556
                             newProtocol.equalsIgnoreCase(context.protocol))) {
557
                 // inherit the protocol handler from the context
558
                 // if not specified to the constructor
559
                 if (handler == null) {
560
                     handler = context.handler;
561
                 }
562
 
563
                 // If the context is a hierarchical URL scheme and the spec
564
                 // contains a matching scheme then maintain backwards
565
                 // compatibility and treat it as if the spec didn't contain
566
                 // the scheme; see 5.2.3 of RFC2396
567
                 if (context.path != null && context.path.startsWith("/"))
568
                     newProtocol = null;
569
 
570
                 if (newProtocol == null) {
571
                      = context.protocol;
572
                      = context.authority;
573
                      = context.userInfo;
574
                      = context.host;
575
                      = context.port;
576
                      = context.file;
577
                      = context.path;
578
                     isRelative = true;
579
                 }
580
             }
581
 
582
             if ( == null) {
583
                 throw new MalformedURLException("no protocol: "+original);
584
             }
585
 
586
             // Get the protocol handler if not specified or the protocol
587
             // of the context could not be used
588
             if (handler == null &&
589
                 (handler = getURLStreamHandler()) == null) {
590
                 throw new MalformedURLException("unknown protocol: "+);
591
             }
592
 
593
             this. = handler;
594
 
595
             i = spec.indexOf('#', start);
596
             if (i >= 0) {
597
                  = spec.substring(i + 1, limit);
598
                 limit = i;
599
             }
600
 
601
             /*
602
              * Handle special case inheritance of query and fragment
603
              * implied by RFC2396 section 5.2.2.
604
              */
605
             if (isRelative && start == limit) {
606
                  = context.query;
607
                 if ( == null) {
608
                      = context.ref;
609
                 }
610
             }
611
 
612
             handler.parseURL(this, spec, start, limit);
613
 
614
         } catch(MalformedURLException e) {
615
             throw e;
616
         } catch(Exception e) {
617
             MalformedURLException exception = new MalformedURLException(e.getMessage());
618
             exception.initCause(e);
619
             throw exception;
620
         }
621
     }
622
 
623
     /*
624
      * Returns true if specified string is a valid protocol name.
625
      */
626
     private boolean isValidProtocol(String protocol) {
627
         int len = protocol.length();
628
         if (len < 1)
629
             return false;
630
         char c = protocol.charAt(0);
631
         if (!Character.isLetter(c))
632
             return false;
633
         for (int i = 1; i < len; i++) {
634
             c = protocol.charAt(i);
635
             if (!Character.isLetterOrDigit(c) && c != '.' && c != '+' &&
636
                 c != '-') {
637
                 return false;
638
             }
639
         }
640
         return true;
641
     }
642
 
643
     /*
644
      * Checks for permission to specify a stream handler.
645
      */
646
     private void checkSpecifyHandler(SecurityManager sm) {
648
     }

    
Sets the fields of the URL. This is not a public method so that only URLStreamHandlers can modify URL fields. URLs are otherwise constant.

Parameters:
protocol the name of the protocol to use
host the name of the host
port the port number on the host
file the file on the host
ref the internal reference in the URL
660
 
661
     protected void set(String protocol, String host,
662
                        int port, String file, String ref) {
663
         synchronized (this) {
664
             this. = protocol;
665
             this. = host;
666
              = port == -1 ? host : host + ":" + port;
667
             this. = port;
668
             this. = file;
669
             this. = ref;
670
             /* This is very important. We must recompute this after the
671
              * URL has been changed. */
672
              = -1;
673
              = null;
674
             int q = file.lastIndexOf('?');
675
             if (q != -1) {
676
                  = file.substring(q+1);
677
                  = file.substring(0, q);
678
             } else
679
                  = file;
680
         }
681
     }

    
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.

Parameters:
protocol the name of the protocol to use
host the name of the host
port the port number on the host
authority the authority part for the url
userInfo the username and password
path the file on the host
ref the internal reference in the URL
query the query part of this URL
Since:
1.3
697
 
698
     protected void set(String protocol, String host, int port,
699
                        String authority, String userInfo, String path,
700
                        String query, String ref) {
701
         synchronized (this) {
702
             this. = protocol;
703
             this. = host;
704
             this. = port;
705
             this. = query == null ? path : path + "?" + query;
706
             this. = userInfo;
707
             this. = path;
708
             this. = ref;
709
             /* This is very important. We must recompute this after the
710
              * URL has been changed. */
711
              = -1;
712
              = null;
713
             this. = query;
714
             this. = authority;
715
         }
716
     }

    
Gets the query part of this URL.

Returns:
the query part of this URL, or null if one does not exist
Since:
1.3
724
 
725
     public String getQuery() {
726
         return ;
727
     }

    
Gets the path part of this URL.

Returns:
the path part of this URL, or an empty string if one does not exist
Since:
1.3
735
 
736
     public String getPath() {
737
         return ;
738
     }

    
Gets the userInfo part of this URL.

Returns:
the userInfo part of this URL, or null if one does not exist
Since:
1.3
746
 
747
     public String getUserInfo() {
748
         return ;
749
     }

    
Gets the authority part of this URL.

Returns:
the authority part of this URL
Since:
1.3
756
 
757
     public String getAuthority() {
758
         return ;
759
     }

    
Gets the port number of this URL.

Returns:
the port number, or -1 if the port is not set
765
 
766
     public int getPort() {
767
         return ;
768
     }

    
Gets the default port number of the protocol associated with this URL. If the URL scheme or the URLStreamHandler for the URL do not define a default port number, then -1 is returned.

Returns:
the port number
Since:
1.4
778
 
779
     public int getDefaultPort() {
780
         return .getDefaultPort();
781
     }

    
Gets the protocol name of this URL.

Returns:
the protocol of this URL.
787
 
788
     public String getProtocol() {
789
         return ;
790
     }

    
Gets the host name of this 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 ('[' and ']').

Returns:
the host name of this URL.
799
 
800
     public String getHost() {
801
         return ;
802
     }

    
Gets the file name of this 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.

Returns:
the file name of this URL, or an empty string if one does not exist
814
 
815
     public String getFile() {
816
         return ;
817
     }

    
Gets the anchor (also known as the "reference") of this URL.

Returns:
the anchor (also known as the "reference") of this URL, or null if one does not exist
825
 
826
     public String getRef() {
827
         return ;
828
     }

    
Compares this URL for equality with another object.

If the given object is not a URL then this method immediately returns 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 equals is known to be inconsistent with virtual hosting in HTTP.

Parameters:
obj the URL to compare against.
Returns:
true if the objects are the same; false otherwise.
854
 
855
     public boolean equals(Object obj) {
856
         if (!(obj instanceof URL))
857
             return false;
858
         URL u2 = (URL)obj;
859
 
860
         return .equals(this, u2);
861
     }

    
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.

Returns:
a hash code for this URL.
870
 
871
     public synchronized int hashCode() {
872
         if ( != -1)
873
             return ;
874
 
875
          = .hashCode(this);
876
         return ;
877
     }

    
Compares two URLs, excluding the fragment component.

Returns true if this URL and the other argument are equal without taking the fragment component into consideration.

Parameters:
other the URL to compare against.
Returns:
true if they reference the same remote object; false otherwise.
889
 
890
     public boolean sameFile(URL other) {
891
         return .sameFile(this, other);
892
     }

    
Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

Returns:
a string representation of this object.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLStreamHandler.toExternalForm(java.net.URL)
903
 
904
     public String toString() {
905
         return toExternalForm();
906
     }

    
Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

Returns:
a string representation of this object.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLStreamHandler.toExternalForm(java.net.URL)
917
 
918
     public String toExternalForm() {
919
         return .toExternalForm(this);
920
     }

    
Returns a URI equivalent to this URL. This method functions in the same way as 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.

Returns:
a URI instance equivalent to this URL.
Throws:
URISyntaxException if this URL is not formatted strictly according to to RFC2396 and cannot be converted to a URI.
Since:
1.5
934
 
935
     public URI toURI() throws URISyntaxException {
936
         return new URI (toString());
937
     }

    
Returns a URLConnection object that represents a connection to the remote object referred to by the URL.

A new connection is opened every time by calling the openConnection method of the protocol handler for this URL.

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.

Returns:
a URLConnection to the URL.
Throws:
java.io.IOException if an I/O exception occurs.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLConnection
URLStreamHandler.openConnection(java.net.URL)
961
 
962
     public URLConnection openConnection() throws java.io.IOException {
963
         return .openConnection(this);
964
     }

    
Same as 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. Calling this method preempts the system's default ProxySelector settings.

Parameters:
proxy the Proxy through which this connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.
Returns:
a URLConnection to the URL.
Throws:
java.io.IOException if an I/O exception occurs.
java.lang.SecurityException if a security manager is present and the caller doesn't have permission to connect to the proxy.
java.lang.IllegalArgumentException will be thrown if proxy is null, or proxy has the wrong type
java.lang.UnsupportedOperationException if the subclass that implements the protocol handler doesn't support this method.
Since:
1.5
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLConnection
URLStreamHandler.openConnection(java.net.URL,java.net.Proxy)
994
 
995
     public URLConnection openConnection(Proxy proxy)
996
         throws java.io.IOException {
997
         if (proxy == null) {
998
             throw new IllegalArgumentException("proxy can not be null");
999
         }
1001
        SecurityManager sm = System.getSecurityManager();
1002
        if (proxy.type() != .. && sm != null) {
1003
            InetSocketAddress epoint = (InetSocketAddress) proxy.address();
1004
            if (epoint.isUnresolved())
1005
                sm.checkConnect(epoint.getHostName(), epoint.getPort());
1006
            else
1007
                sm.checkConnect(epoint.getAddress().getHostAddress(),
1008
                                epoint.getPort());
1009
        }
1010
        return .openConnection(this, proxy);
1011
    }

    
Opens a connection to this URL and returns an InputStream for reading from that connection. This method is a shorthand for: 
     openConnection().getInputStream()

Returns:
an input stream for reading from the URL connection.
Throws:
java.io.IOException if an I/O exception occurs.
See also:
openConnection()
URLConnection.getInputStream()
1026
    public final InputStream openStream() throws java.io.IOException {
1027
        return openConnection().getInputStream();
1028
    }

    
Gets the contents of this URL. This method is a shorthand for: 
     openConnection().getContent()

Returns:
the contents of this URL.
Throws:
java.io.IOException if an I/O exception occurs.
See also:
URLConnection.getContent()
1040
    public final Object getContent() throws java.io.IOException {
1041
        return openConnection().getContent();
1042
    }

    
Gets the contents of this URL. This method is a shorthand for: 
     openConnection().getContent(Class[])

Parameters:
classes an array of Java types
Returns:
the content object of this URL that is the first match of the types specified in the classes array. null if none of the requested types are supported.
Throws:
java.io.IOException if an I/O exception occurs.
Since:
1.3
See also:
URLConnection.getContent(java.lang.Class[])
1058
    public final Object getContent(Class[] classes)
1059
    throws java.io.IOException {
1060
        return openConnection().getContent(classes);
1061
    }

    
The URLStreamHandler factory. 
1066
    static URLStreamHandlerFactory factory;

    
Sets an application's URLStreamHandlerFactory. This method can be called at most once in a given Java Virtual Machine.

The 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 checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

Parameters:
fac the desired factory.
Throws:
java.lang.Error if the application has already set a factory.
java.lang.SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.
See also:
java.net.URL.URL(java.lang.String,java.lang.String,int,java.lang.String)
URLStreamHandlerFactory
java.lang.SecurityManager.checkSetFactory()
1091
    public static void setURLStreamHandlerFactory(URLStreamHandlerFactory fac) {
1092
        synchronized () {
1093
            if ( != null) {
1094
                throw new Error("factory already defined");
1095
            }
1096
            SecurityManager security = System.getSecurityManager();
1097
            if (security != null) {
1098
                security.checkSetFactory();
1099
            }
1100
            .clear();
1101
             = fac;
1102
        }
1103
    }

    
A table of protocol handlers. 
1108
    static Hashtable handlers = new Hashtable();
1109
    private static Object streamHandlerLock = new Object();

    
Returns the Stream Handler.

Parameters:
protocol the protocol to use
1115
    static URLStreamHandler getURLStreamHandler(String protocol) {
1117
        URLStreamHandler handler = (URLStreamHandler).get(protocol);
1118
        if (handler == null) {
1120
            boolean checkedWithFactory = false;
1122
            // Use the factory (if any)
1123
            if ( != null) {
1124
                handler = .createURLStreamHandler(protocol);
1125
                checkedWithFactory = true;
1126
            }
1128
            // Try java protocol handler
1129
            if (handler == null) {
1130
                String packagePrefixList = null;
1132
                packagePrefixList
1133
                    = java.security.AccessController.doPrivileged(
1134
                    new sun.security.action.GetPropertyAction(
1135
                        ,""));
1136
                if (packagePrefixList != "") {
1137
                    packagePrefixList += "|";
1138
                }
1140
                // REMIND: decide whether to allow the "null" class prefix
1141
                // or not.
1142
                packagePrefixList += "sun.net.www.protocol";
1144
                StringTokenizer packagePrefixIter =
1145
                    new StringTokenizer(packagePrefixList, "|");
1147
                while (handler == null &&
1148
                       packagePrefixIter.hasMoreTokens()) {
1150
                    String packagePrefix =
1151
                      packagePrefixIter.nextToken().trim();
1152
                    try {
1153
                        String clsName = packagePrefix + "." + protocol +
1154
                          ".Handler";
1155
                        Class cls = null;
1156
                        try {
1157
                            cls = Class.forName(clsName);
1158
                        } catch (ClassNotFoundException e) {
1159
                            ClassLoader cl = ClassLoader.getSystemClassLoader();
1160
                            if (cl != null) {
1161
                                cls = cl.loadClass(clsName);
1162
                            }
1163
                        }
1164
                        if (cls != null) {
1165
                            handler  =
1166
                              (URLStreamHandler)cls.newInstance();
1167
                        }
1168
                    } catch (Exception e) {
1169
                        // any number of exceptions can get thrown here
1170
                    }
1171
                }
1172
            }
1174
            synchronized () {
1176
                URLStreamHandler handler2 = null;
1178
                // Check again with hashtable just in case another
1179
                // thread created a handler since we last checked
1180
                handler2 = (URLStreamHandler).get(protocol);
1182
                if (handler2 != null) {
1183
                    return handler2;
1184
                }
1186
                // Check with factory if another thread set a
1187
                // factory since our last check
1188
                if (!checkedWithFactory &&  != null) {
1189
                    handler2 = .createURLStreamHandler(protocol);
1190
                }
1192
                if (handler2 != null) {
1193
                    // The handler from the factory must be given more
1194
                    // importance. Discard the default handler that
1195
                    // this thread created.
1196
                    handler = handler2;
1197
                }
1199
                // Insert this handler into the hashtable
1200
                if (handler != null) {
1201
                    .put(protocol, handler);
1202
                }
1204
            }
1205
        }
1207
        return handler;
1209
    }

    
WriteObject is called to save the state of the URL to an ObjectOutputStream. The handler is not saved since it is specific to this system.

SerialData:
the default write object value. When read back in, the reader must ensure that calling getURLStreamHandler with the protocol variable returns a valid URLStreamHandler and throw an IOException if it does not.
1221
    private synchronized void writeObject(java.io.ObjectOutputStream s)
1222
        throws IOException
1223
    {
1224
        s.defaultWriteObject(); // write the fields
1225
    }

    
readObject is called to restore the state of the URL from the stream. It reads the components of the URL and finds the local stream handler. 
1232
    private synchronized void readObject(java.io.ObjectInputStream s)
1233
         throws IOException, ClassNotFoundException
1234
    {
1235
        s.defaultReadObject();  // read the fields
1236
        if (( = getURLStreamHandler()) == null) {
1237
            throw new IOException("unknown protocol: " + );
1238
        }
1240
        // Construct authority part
1241
        if ( == null &&
1242
            (( != null && .length() > 0) ||  != -1)) {
1243
            if ( == null)
1244
                 = "";
1245
             = ( == -1) ?  :  + ":" + ;
1247
            // Handle hosts with userInfo in them
1248
            int at = .lastIndexOf('@');
1249
            if (at != -1) {
1250
                 = .substring(0, at);
1251
                 = .substring(at+1);
1252
            }
1253
        } else if ( != null) {
1254
            // Construct user info part
1255
            int ind = .indexOf('@');
1256
            if (ind != -1)
1257
                 = .substring(0, ind);
1258
        }
1260
        // Construct path and query part
1261
         = null;
1262
         = null;
1263
        if ( != null) {
1264
            // Fix: only do this if hierarchical?
1265
            int q = .lastIndexOf('?');
1266
            if (q != -1) {
1267
                 = .substring(q+1);
1268
                 = .substring(0, q);
1269
            } else
1270
                 = ;
1271
        }
1272
    }
1275
class Parts {
1276
    String path, query, ref;
1278
    Parts(String file) {
1279
        int ind = file.indexOf('#');
1280
         = ind < 0 ? null: file.substring(ind + 1);
1281
        file = ind < 0 ? file: file.substring(0, ind);
1282
        int q = file.lastIndexOf('?');
1283
        if (q != -1) {
1284
             = file.substring(q+1);
1285
             = file.substring(0, q);
1286
        } else {
1287
             = file;
1288
        }
1289
    }
1291
    String getPath() {
1292
        return ;
1293
    }
1295
    String getQuery() {
1296
        return ;
1297
    }
1299
    String getRef() {
1300
        return ;
1301
    }
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