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package java.net;
import java.io.IOException;
The abstract class ContentHandler is the superclass of all classes that read an Object from a URLConnection. An application does not generally call the getContent method in this class directly. Instead, an application calls the getContent method in class URL or in URLConnection. The application's content handler factory (an instance of a class that implements the interface ContentHandlerFactory set up by a call to
setContentHandlerFactory is called with a String giving the MIME type of the object being received on the socket. The factory returns an instance of a subclass of ContentHandler, and its getContent method is called to create the object.
If no content handler could be found, URLConnection will look for a content handler in a user-definable set of places. Users can define a vertical-bar delimited set of class prefixes to search through by defining the URLConnection.contentPathProp
property. The class name must be of the form:
{package-prefix}.{major}.{minor}
where {major}.{minor} is formed by taking the content-type string, replacing all slash characters with a period ('.'), and all other non-alphanumeric characters with the underscore character '_'. The alphanumeric characters are specifically the 26 uppercase ASCII letters 'A' through 'Z', the 26 lowercase ASCII letters 'a' through 'z', and the 10 ASCII digits '0' through '9'.
e.g.
YoyoDyne.experimental.text.plain
If no user-defined content handler is found, then the system
tries to load a specific content-type handler from one
of the built-in handlers, if one exists.
If the loading of the content handler class would be performed by
a classloader that is outside of the delegation chain of the caller,
the JVM will need the RuntimePermission "getClassLoader".
Author: James Gosling See Also: Since: 1.0
/**
* The abstract class {@code ContentHandler} is the superclass
* of all classes that read an {@code Object} from a
* {@code URLConnection}.
* <p>
* An application does not generally call the
* {@code getContent} method in this class directly. Instead, an
* application calls the {@code getContent} method in class
* {@code URL} or in {@code URLConnection}.
* The application's content handler factory (an instance of a class that
* implements the interface {@code ContentHandlerFactory} set up by a call to
* {@link URLConnection#setContentHandlerFactory(ContentHandlerFactory)
* setContentHandlerFactory} is called with a {@code String} giving the
* MIME type of the object being received on the socket. The factory returns an
* instance of a subclass of {@code ContentHandler}, and its
* {@code getContent} method is called to create the object.
* <p>
* If no content handler could be {@linkplain URLConnection#getContent() found},
* URLConnection will look for a content handler in a user-definable set of places.
* Users can define a vertical-bar delimited set of class prefixes
* to search through by defining the <i>{@link java.net.URLConnection#contentPathProp}</i>
* property. The class name must be of the form:
* <blockquote>
* <i>{package-prefix}.{major}.{minor}</i>
* <p>
* where <i>{major}.{minor}</i> is formed by taking the
* content-type string, replacing all slash characters with a
* {@code period} ('.'), and all other non-alphanumeric characters
* with the underscore character '{@code _}'. The alphanumeric
* characters are specifically the 26 uppercase ASCII letters
* '{@code A}' through '{@code Z}', the 26 lowercase ASCII
* letters '{@code a}' through '{@code z}', and the 10 ASCII
* digits '{@code 0}' through '{@code 9}'.
* <p>
* e.g.
* YoyoDyne.experimental.text.plain
* </blockquote>
* If no user-defined content handler is found, then the system
* tries to load a specific <i>content-type</i> handler from one
* of the built-in handlers, if one exists.
* <p>
* If the loading of the content handler class would be performed by
* a classloader that is outside of the delegation chain of the caller,
* the JVM will need the RuntimePermission "getClassLoader".
*
* @author James Gosling
* @see java.net.ContentHandler#getContent(java.net.URLConnection)
* @see java.net.ContentHandlerFactory
* @see java.net.URL#getContent()
* @see java.net.URLConnection
* @see java.net.URLConnection#getContent()
* @see java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
* @since 1.0
*/
public abstract class ContentHandler {
Given a URL connect stream positioned at the beginning of the
representation of an object, this method reads that stream and
creates an object from it.
Params: - urlc – a URL connection.
Throws: - IOException – if an I/O error occurs while reading the object.
Returns: the object read by the ContentHandler.
/**
* Given a URL connect stream positioned at the beginning of the
* representation of an object, this method reads that stream and
* creates an object from it.
*
* @param urlc a URL connection.
* @return the object read by the {@code ContentHandler}.
* @exception IOException if an I/O error occurs while reading the object.
*/
public abstract Object getContent(URLConnection urlc) throws IOException;
Given a URL connect stream positioned at the beginning of the representation of an object, this method reads that stream and creates an object that matches one of the types specified. The default implementation of this method should call getContent(URLConnection) and screen the return type for a match of the suggested types. Params: - urlc – a URL connection.
- classes – an array of types requested
Throws: - IOException – if an I/O error occurs while reading the object.
Returns: the object read by the ContentHandler that is the first match of the suggested types or null if none of the requested are supported. Since: 1.3
/**
* Given a URL connect stream positioned at the beginning of the
* representation of an object, this method reads that stream and
* creates an object that matches one of the types specified.
*
* The default implementation of this method should call
* {@link #getContent(URLConnection)}
* and screen the return type for a match of the suggested types.
*
* @param urlc a URL connection.
* @param classes an array of types requested
* @return the object read by the {@code ContentHandler} that is
* the first match of the suggested types or
* {@code null} if none of the requested are supported.
* @exception IOException if an I/O error occurs while reading the object.
* @since 1.3
*/
@SuppressWarnings("rawtypes")
public Object getContent(URLConnection urlc, Class[] classes) throws IOException {
Object obj = getContent(urlc);
for (Class<?> c : classes) {
if (c.isInstance(obj)) {
return obj;
}
}
return null;
}
}