java.net

Class URLStreamHandler

java.lang.Object

java.net.URLStreamHandler

public abstract class URLStreamHandler
extends Object

The abstract class 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.

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.

Since:

JDK1.0

Version:

1.48 10/27/00

Author:

James Gosling

See Also:

URL.URL(java.lang.String, java.lang.String, int, java.lang.String)

Constructor Summary

Constructors

Constructor and Description
URLStreamHandler()

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	equals(URL u1, URL u2) Provides the default equals calculation.
protected int	getDefaultPort() Returns the default port for a URL parsed by this handler.
protected InetAddress	getHostAddress(URL u) Get the IP address of our host.
protected int	hashCode(URL u) Provides the default hash calculation.
protected boolean	hostsEqual(URL u1, URL u2) Compares the host components of two URLs.
protected abstract URLConnection	openConnection(URL u) Opens a connection to the object referenced by the URL argument.
protected void	parseURL(URL u, String spec, int start, int limit) Parses the string representation of a URL into a URL object.
protected boolean	sameFile(URL u1, URL u2) Compare two urls to see whether they refer to the same file, i.e., having the same protocol, host, port, and path.
protected void	setURL(URL u, String protocol, String host, int port, String authority, String userInfo, String path, String query, String ref) Sets the fields of the URL argument to the indicated values.
protected String	toExternalForm(URL u) Converts a URL of a specific protocol to a String.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

URLStreamHandler

public URLStreamHandler()

Method Detail

openConnection

protected abstract URLConnection openConnection(URL u)
                                         throws IOException

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. NOTE: java.net.HttpURLConnection is found in J2ME CDC profiles such as J2ME Foundation Profile.

Parameters:

u - the URL that this connects to.

Returns:

a URLConnection object for the URL.

Throws:

IOException - if an I/O error occurs while opening the connection.

parseURL

protected void parseURL(URL u,
            String spec,
            int start,
            int limit)

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.

Parameters:

u - the URL to receive the result of parsing the spec.

spec - the String representing the URL that must be parsed.

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.

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.

getDefaultPort

protected int getDefaultPort()

Returns the default port for a URL parsed by this handler. This method is meant to be overidden by handlers with default port numbers.

Returns:

the default port for a URL parsed by this handler.

equals

protected boolean equals(URL u1,
             URL u2)

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.

Parameters:

u1 - a URL object

u2 - a URL object

Returns:

true if the two urls are considered equal, ie. they refer to the same fragment in the same file.

hashCode

protected int hashCode(URL u)

Provides the default hash calculation. May be overidden by handlers for other protocols that have different requirements for hashCode calculation.

Parameters:

u - a URL object

Returns:

an int suitable for hash table indexing

sameFile

protected boolean sameFile(URL u1,
               URL u2)

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.

Parameters:

u1 - a URL object

u2 - a URL object

Returns:

true if u1 and u2 refer to the same file

getHostAddress

protected InetAddress getHostAddress(URL u)

Get the IP address of our host. An empty host field or a DNS failure will result in a null return.

Parameters:

u - a URL object

Returns:

an InetAddress representing the host IP address.

hostsEqual

protected boolean hostsEqual(URL u1,
                 URL u2)

Compares the host components of two URLs.

Parameters:

u1 - the URL of the first host to compare

u2 - the URL of the second host to compare

Returns:

true if and only if they are equal, false otherwise.

toExternalForm

protected String toExternalForm(URL u)

Converts a URL of a specific protocol to a String.

Parameters:

u - the URL.

Returns:

a string representation of the URL argument.

setURL

protected void setURL(URL u,
          String protocol,
          String host,
          int port,
          String authority,
          String userInfo,
          String path,
          String query,
          String 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.

Parameters:

u - the URL to modify.

protocol - the protocol name.

host - the remote host value for the URL.

port - the port on the remote machine.

authority - the authority part for the URL.

userInfo - the userInfo part of the URL.

path - the path component of the URL.

query - the query part for the URL.

ref - the reference.

Throws:

SecurityException - if the protocol handler of the URL is different from this one

See Also:

URL.set(java.lang.String, java.lang.String, int, java.lang.String, java.lang.String)