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 or https.

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:
1.0
See Also:

Constructor Summary

Constructor Description
URLStreamHandler()
Constructor for subclasses to call.

Method Summary

Modifier and Type Method 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 URLConnection openConnection(URL u, Proxy p)
Same as openConnection(URL), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection.
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 file, String ref)
Deprecated.
Use setURL(URL, String, String, int, String, String, String, String);
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 declared in class java.lang.Object

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

Constructor Details

URLStreamHandler

public URLStreamHandler()
Constructor for subclasses to call.

Method Details

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.

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.

openConnection

protected URLConnection openConnection(URL u, Proxy p) throws IOException
Same as openConnection(URL), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection.

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

Implementation Requirements:
The default implementation of this method first checks that the given URL and Proxy are not null, then throws UnsupportedOperationException. Subclasses should override this method with an appropriate implementation.
Parameters:
u - the URL that this connects to.
p - the proxy through which the connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.
Returns:
a URLConnection object for the URL.
Throws:
IOException - if an I/O error occurs while opening the connection.
IllegalArgumentException - if either u or p is null, or p has the wrong type.
UnsupportedOperationException - if the subclass that implements the protocol doesn't support this method.
Since:
1.5

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 overridden by handlers with default port numbers.
Returns:
the default port for a URL parsed by this handler.
Since:
1.3

equals

protected boolean equals(URL u1, URL u2)
Provides the default equals calculation. May be overridden 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, i.e. they refer to the same fragment in the same file.
Since:
1.3

hashCode

protected int hashCode(URL u)
Provides the default hash calculation. May be overridden 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
Since:
1.3

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
Since:
1.3

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.
Since:
1.3

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.
Since:
1.3

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 able to use this method to set the values of the URL fields.
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
Since:
1.3

setURL

@Deprecated protected void setURL(URL u, String protocol, String host, int port, String file, String ref)
Deprecated.
Use setURL(URL, String, String, int, String, String, String, String);
Sets the fields of the URL argument to the indicated values. Only classes derived from URLStreamHandler are able to use this method to set the values of the URL fields.
Parameters:
u - the URL to modify.
protocol - the protocol name. This value is ignored since 1.2.
host - the remote host value for the URL.
port - the port on the remote machine.
file - the file.
ref - the reference.
Throws:
SecurityException - if the protocol handler of the URL is different from this one

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