org.xhtmlrenderer.swing

Class NaiveUserAgent

java.lang.Object

org.xhtmlrenderer.swing.NaiveUserAgent

All Implemented Interfaces:

DocumentListener, UserAgentCallback

public class NaiveUserAgent
extends java.lang.Object
implements UserAgentCallback, DocumentListener

NaiveUserAgent is a simple implementation of UserAgentCallback which places no restrictions on what XML, CSS or images are loaded, and reports visited links without any filtering. The most straightforward process available in the JDK is used to load the resources in question--either using java.io or java.net classes.

The NaiveUserAgent has a small cache for images, the size of which (number of images) can be passed as a constructor argument. There is no automatic cleaning of the cache; call shrinkImageCache() to remove the least-accessed elements--for example, you might do this when a new document is about to be loaded. The NaiveUserAgent is also a DocumentListener; if registered with a source of document events (like the panel hierarchy), it will respond to the DocumentListener.documentStarted() call and attempt to shrink its cache.

This class is meant as a starting point--it will work out of the box, but you should really implement your own, tuned to your application's needs.

Author:

Torbjoern Gannholm

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.LinkedHashMap	_imageCache a (simple) LRU cache

Constructor Summary

Constructors

Constructor and Description
NaiveUserAgent() Creates a new instance of NaiveUserAgent with a max image cache of 16 images.
NaiveUserAgent(int imgCacheSize) Creates a new NaiveUserAgent with a cache of a specific size.

Method Summary

Methods

Modifier and Type	Method and Description
void	clearImageCache() Empties the image cache entirely.
protected ImageResource	createImageResource(java.lang.String uri, java.awt.Image img) Factory method to generate ImageResources from a given Image.
void	documentLoaded() Indicates document layout has complete, e.g.
void	documentStarted() Indicates document has been requested (e.g.
java.lang.String	getBaseURL() Returns the current baseUrl for this class.
byte[]	getBinaryResource(java.lang.String uri) Retrieves a binary resource located at a given URI and returns its contents as a byte array or null if the resource could not be loaded.
CSSResource	getCSSResource(java.lang.String uri) Retrieves the CSS located at the given URI.
ImageResource	getImageResource(java.lang.String uri) Retrieves the image located at the given URI.
XMLResource	getXMLResource(java.lang.String uri) Retrieves the XML located at the given URI.
boolean	isVisited(java.lang.String uri) Returns true if the given URI was visited, meaning it was requested at some point since initialization.
void	onLayoutException(java.lang.Throwable t) Called when document layout failed with an exception.
void	onRenderException(java.lang.Throwable t) Called when document render failed with an exception.
protected java.io.InputStream	resolveAndOpenStream(java.lang.String uri) Gets a Reader for the resource identified
java.lang.String	resolveURI(java.lang.String uri) Resolves the URI; if absolute, leaves as is, if relative, returns an absolute URI based on the baseUrl for the agent.
void	setBaseURL(java.lang.String url) URL relative to which URIs are resolved.
void	shrinkImageCache() If the image cache has more items than the limit specified for this class, the least-recently used will be dropped from cache until it reaches the desired size.

Methods inherited from class java.lang.Object

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

Field Detail

_imageCache

protected java.util.LinkedHashMap _imageCache

a (simple) LRU cache

Constructor Detail

NaiveUserAgent

public NaiveUserAgent()

Creates a new instance of NaiveUserAgent with a max image cache of 16 images.

NaiveUserAgent

public NaiveUserAgent(int imgCacheSize)

Creates a new NaiveUserAgent with a cache of a specific size.

Parameters:

imgCacheSize - Number of images to hold in cache before LRU images are released.

Method Detail

shrinkImageCache

public void shrinkImageCache()

If the image cache has more items than the limit specified for this class, the least-recently used will be dropped from cache until it reaches the desired size.

clearImageCache

public void clearImageCache()

Empties the image cache entirely.

resolveAndOpenStream

protected java.io.InputStream resolveAndOpenStream(java.lang.String uri)

Gets a Reader for the resource identified

Parameters:

uri - PARAM

Returns:

The stylesheet value

getCSSResource

public CSSResource getCSSResource(java.lang.String uri)

Retrieves the CSS located at the given URI. It's assumed the URI does point to a CSS file--the URI will be accessed (using java.io or java.net), opened, read and then passed into the CSS parser. The result is packed up into an CSSResource for later consumption.

Specified by:

getCSSResource in interface UserAgentCallback

Parameters:

uri - Location of the CSS source.

Returns:

A CSSResource containing the parsed CSS.

getImageResource

public ImageResource getImageResource(java.lang.String uri)

Retrieves the image located at the given URI. It's assumed the URI does point to an image--the URI will be accessed (using java.io or java.net), opened, read and then passed into the JDK image-parsing routines. The result is packed up into an ImageResource for later consumption.

Specified by:

getImageResource in interface UserAgentCallback

Parameters:

uri - Location of the image source.

Returns:

An ImageResource containing the image.

createImageResource

protected ImageResource createImageResource(java.lang.String uri,
                                java.awt.Image img)

Factory method to generate ImageResources from a given Image. May be overridden in subclass.

Parameters:

uri - The URI for the image, resolved to an absolute URI.

img - The image to package; may be null (for example, if image could not be loaded).

Returns:

An ImageResource containing the image.

getXMLResource

public XMLResource getXMLResource(java.lang.String uri)

Retrieves the XML located at the given URI. It's assumed the URI does point to a XML--the URI will be accessed (using java.io or java.net), opened, read and then passed into the XML parser (XMLReader) configured for Flying Saucer. The result is packed up into an XMLResource for later consumption.

Specified by:

getXMLResource in interface UserAgentCallback

Parameters:

uri - Location of the XML source.

Returns:

An XMLResource containing the image.

getBinaryResource

public byte[] getBinaryResource(java.lang.String uri)

Description copied from interface: UserAgentCallback

Retrieves a binary resource located at a given URI and returns its contents as a byte array or null if the resource could not be loaded.

Specified by:

getBinaryResource in interface UserAgentCallback

isVisited

public boolean isVisited(java.lang.String uri)

Returns true if the given URI was visited, meaning it was requested at some point since initialization.

Specified by:

isVisited in interface UserAgentCallback

Parameters:

uri - A URI which might have been visited.

Returns:

Always false; visits are not tracked in the NaiveUserAgent.

setBaseURL

public void setBaseURL(java.lang.String url)

URL relative to which URIs are resolved.

Specified by:

setBaseURL in interface UserAgentCallback

Parameters:

url - A URI which anchors other, possibly relative URIs.

resolveURI

public java.lang.String resolveURI(java.lang.String uri)

Resolves the URI; if absolute, leaves as is, if relative, returns an absolute URI based on the baseUrl for the agent.

Specified by:

resolveURI in interface UserAgentCallback

Parameters:

uri - A URI, possibly relative.

Returns:

A URI as String, resolved, or null if there was an exception (for example if the URI is malformed).

getBaseURL

public java.lang.String getBaseURL()

Returns the current baseUrl for this class.

Specified by:

getBaseURL in interface UserAgentCallback

Returns:

the base uri, possibly in the implementations private uri-space

documentStarted

public void documentStarted()

Description copied from interface: DocumentListener

Indicates document has been requested (e.g. a new document is going to be loaded). This will be called before any activity takes place for the document.

Specified by:

documentStarted in interface DocumentListener

documentLoaded

public void documentLoaded()

Description copied from interface: DocumentListener

Indicates document layout has complete, e.g. document is fully "loaded" for display; this is not a callback for the document source (e.g. XML) being loaded. This method will be called on every layout run (including, for example, after panel resizes).

Specified by:

documentLoaded in interface DocumentListener

onLayoutException

public void onLayoutException(java.lang.Throwable t)

Description copied from interface: DocumentListener

Called when document layout failed with an exception. All Throwable objects thrown (except for ThreadDeath) during layout and not otherwise handled will be provided to this method. If a DocumentListener has been defined an XHTML panel, the listener is entirely responsible for handling the exception. No other action will be taken.

Specified by:

onLayoutException in interface DocumentListener

onRenderException

public void onRenderException(java.lang.Throwable t)

Description copied from interface: DocumentListener

Called when document render failed with an exception. All Throwable objects thrown (except for ThreadDeath) during render and not otherwise handled will be provided to this method. If a DocumentListener has been defined an XHTML panel, the listener is entirely responsible for handling the exception. No other action will be taken.

Specified by:

onRenderException in interface DocumentListener