IcedTea-Web
NetX

net.sourceforge.jnlp.cache
Class ResourceTracker

java.lang.Object
  extended by net.sourceforge.jnlp.cache.ResourceTracker

public class ResourceTracker
extends java.lang.Object

This class tracks the downloading of various resources of a JNLP file to local files in the cache. It can be used to download icons, jnlp and extension files, jars, and jardiff files using the version based protocol or any file using the basic download protocol (jardiff and version not implemented yet).

The resource tracker can be configured to prefetch resources, which are downloaded in the order added to the media tracker.

Multiple threads are used to download and cache resources that are actively being waited for (blocking a caller) or those that have been started downloading by calling the startDownload method. Resources that are prefetched are downloaded one at a time and only if no other trackers have requested downloads. This allows the tracker to start downloading many items without using many system resources, but still quickly download items as needed.


Constructor Summary
ResourceTracker()
          Creates a resource tracker that does not prefetch resources.
ResourceTracker(boolean prefetch)
          Creates a resource tracker.
 
Method Summary
 void addDownloadListener(DownloadListener listener)
          Adds the listener to the list of objects interested in receivind DownloadEvents.
 void addResource(java.net.URL location, Version version, DownloadOptions options, UpdatePolicy updatePolicy)
          Add a resource identified by the specified location and version.
 boolean checkResource(java.net.URL location)
          Returns whether a resource is available for use (ie, can be accessed with the getCacheFile method).
protected  void fireDownloadEvent(Resource resource)
          Fires the download event corresponding to the resource's state.
 long getAmountRead(java.net.URL location)
          Returns the number of bytes downloaded for a resource.
 java.io.File getCacheFile(java.net.URL location)
          Returns a file containing the downloaded resource.
 java.net.URL getCacheURL(java.net.URL location)
          Returns a URL pointing to the cached location of the resource, or the resource itself if it is a non-cacheable resource.
 java.io.InputStream getInputStream(java.net.URL location)
          Returns an input stream that reads the contents of the resource.
 long getTotalSize(java.net.URL location)
          Returns the number of total size in bytes of a resource, or -1 it the size is not known.
 void removeDownloadListener(DownloadListener listener)
          Removes a download listener.
 void removeResource(java.net.URL location)
          Removes a resource from the tracker.
 boolean startResource(java.net.URL location)
          Starts loading the resource if it is not already being downloaded or already cached.
protected  void startThread()
          Start a new download thread if there are not too many threads already running.
 boolean waitForResource(java.net.URL location, long timeout)
          Wait for a particular resource to be downloaded and made available.
 boolean waitForResources(java.net.URL[] urls, long timeout)
          Wait for a group of resources to be downloaded and made available locally.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ResourceTracker

public ResourceTracker()
Creates a resource tracker that does not prefetch resources.


ResourceTracker

public ResourceTracker(boolean prefetch)
Creates a resource tracker.

Parameters:
prefetch - whether to download resources before requested.
Method Detail

addResource

public void addResource(java.net.URL location,
                        Version version,
                        DownloadOptions options,
                        UpdatePolicy updatePolicy)
Add a resource identified by the specified location and version. The tracker only downloads one version of a given resource per instance (ie cannot download both versions 1 and 2 of a resource in the same tracker).

Parameters:
location - the location of the resource
version - the resource version
updatePolicy - whether to check for updates if already in cache

removeResource

public void removeResource(java.net.URL location)
Removes a resource from the tracker. This method is useful to allow memory to be reclaimed, but calling this method is not required as resources are reclaimed when the tracker is collected.

Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked

addDownloadListener

public void addDownloadListener(DownloadListener listener)
Adds the listener to the list of objects interested in receivind DownloadEvents.

Parameters:
listener - the listener to add.

removeDownloadListener

public void removeDownloadListener(DownloadListener listener)
Removes a download listener.

Parameters:
listener - the listener to remove.

fireDownloadEvent

protected void fireDownloadEvent(Resource resource)
Fires the download event corresponding to the resource's state. This method is typicall called by the Resource itself on each tracker that is monitoring the resource. Do not call this method with any locks because the listeners may call back to this ResourceTracker.


getCacheURL

public java.net.URL getCacheURL(java.net.URL location)
Returns a URL pointing to the cached location of the resource, or the resource itself if it is a non-cacheable resource.

If the resource has not downloaded yet, the method will block until it has been transferred to the cache.

Parameters:
location - the resource location
Returns:
the resource, or null if it could not be downloaded
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked
See Also:
CacheUtil.isCacheable(java.net.URL, net.sourceforge.jnlp.Version)

getCacheFile

public java.io.File getCacheFile(java.net.URL location)
Returns a file containing the downloaded resource. If the resource is non-cacheable then null is returned unless the resource is a local file (the original file is returned).

If the resource has not downloaded yet, the method will block until it has been transferred to the cache.

Parameters:
location - the resource location
Returns:
a local file containing the resource, or null
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked
See Also:
CacheUtil.isCacheable(java.net.URL, net.sourceforge.jnlp.Version)

getInputStream

public java.io.InputStream getInputStream(java.net.URL location)
                                   throws java.io.IOException
Returns an input stream that reads the contents of the resource. For non-cacheable resources, an InputStream that reads from the source location is returned. Otherwise the InputStream reads the cached resource.

This method will block while the resource is downloaded to the cache.

Throws:
java.io.IOException - if there was an error opening the stream
java.lang.IllegalArgumentException - if the resource is not being tracked

waitForResources

public boolean waitForResources(java.net.URL[] urls,
                                long timeout)
                         throws java.lang.InterruptedException
Wait for a group of resources to be downloaded and made available locally.

Parameters:
urls - the resources to wait for
timeout - the time in ms to wait before returning, 0 for no timeout
Returns:
whether the resources downloaded before the timeout
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked
java.lang.InterruptedException

waitForResource

public boolean waitForResource(java.net.URL location,
                               long timeout)
                        throws java.lang.InterruptedException
Wait for a particular resource to be downloaded and made available.

Parameters:
location - the resource to wait for
timeout - the timeout, or 0 to wait until completed
Returns:
whether the resource downloaded before the timeout
Throws:
java.lang.InterruptedException - if another thread interrupted the wait
java.lang.IllegalArgumentException - if the resource is not being tracked

getAmountRead

public long getAmountRead(java.net.URL location)
Returns the number of bytes downloaded for a resource.

Parameters:
location - the resource location
Returns:
the number of bytes transferred
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked

checkResource

public boolean checkResource(java.net.URL location)
Returns whether a resource is available for use (ie, can be accessed with the getCacheFile method).

Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked

startResource

public boolean startResource(java.net.URL location)
Starts loading the resource if it is not already being downloaded or already cached. Resources started downloading using this method may download faster than those prefetched by the tracker because the tracker will only prefetch one resource at a time to conserve system resources.

Returns:
true if the resource is already downloaded (or an error occurred)
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked

getTotalSize

public long getTotalSize(java.net.URL location)
Returns the number of total size in bytes of a resource, or -1 it the size is not known.

Parameters:
location - the resource location
Returns:
the number of bytes, or -1
Throws:
java.lang.IllegalArgumentException - if the resource is not being tracked

startThread

protected void startThread()
Start a new download thread if there are not too many threads already running.

Calls to this method should be synchronized on lock.


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