[JAVA API] java.net.URL

java.net

Class URL

• java.lang.Object
• • java.net.URL

• All Implemented Interfaces:

  Serializable

  ---

  
  

  public final class URL
  extends Object
  implements Serializable

  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 pathcomponent.

  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.

  Since:

  JDK1.0

  See Also:

  Serialized Form

• • Constructor Summary

    Constructors 

    Constructor and Description
    URL(String spec) Creates a URL object from the String representation.
    URL(String protocol, String host, int port, String file) Creates a URL object from the specified protocol, host, port number, and file.
    URL(String protocol, String host, int port, String file, URLStreamHandler handler) Creates a URL object from the specified protocol, host, port number, file, and handler.
    URL(String protocol, String host, String file) Creates a URL from the specified protocol name, host name, and file name.
    URL(URL context, String spec) Creates a URL by parsing the given spec within a specified context.
    URL(URL context, String spec, URLStreamHandler handler) Creates a URL by parsing the given spec with the specified handler within a specified context.

• Method Summary

  Methods 

  Modifier and Type	Method and Description
  boolean	equals(Object obj) Compares this URL for equality with another object.
  String	getAuthority() Gets the authority part of this URL.
  Object	getContent() Gets the contents of this URL.
  Object	getContent(Class[] classes) Gets the contents of this URL.
  int	getDefaultPort() Gets the default port number of the protocol associated with this URL.
  String	getFile() Gets the file name of this URL.
  String	getHost() Gets the host name of this URL, if applicable.
  String	getPath() Gets the path part of this URL.
  int	getPort() Gets the port number of this URL.
  String	getProtocol() Gets the protocol name of this URL.
  String	getQuery() Gets the query part of this URL.
  String	getRef() Gets the anchor (also known as the "reference") of this URL.
  String	getUserInfo() Gets the userInfo part of this URL.
  int	hashCode() Creates an integer suitable for hash table indexing.
  URLConnection	openConnection() Returns a URLConnection instance that represents a connection to the remote object referred to by the URL.
  URLConnection	openConnection(Proxy proxy) 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.
  InputStream	openStream() Opens a connection to this URL and returns an InputStream for reading from that connection.
  boolean	sameFile(URL other) Compares two URLs, excluding the fragment component.
  protected void	set(String protocol, String host, int port, String file, String ref) Sets the fields of the URL.
  protected void	set(String protocol, String host, int port, String authority, String userInfo,String path, String query, String ref) Sets the specified 8 fields of the URL.
  static void	setURLStreamHandlerFactory(URLStreamHandlerFactory fac) Sets an application's URLStreamHandlerFactory.
  String	toExternalForm() Constructs a string representation of this URL.
  String	toString() Constructs a string representation of this URL.
  URI	toURI() Returns a URI equivalent to this URL.

• Methods inherited from class java.lang.Object

  clone, finalize, getClass, notify, notifyAll, wait, wait, wait