org.wandora.modules.servlet

Class CachedAction.OutputProvider

java.lang.Object

org.wandora.modules.servlet.CachedAction.OutputProvider

Enclosing class:

CachedAction

public class CachedAction.OutputProvider
extends java.lang.Object

A class used to pass an output stream to the doOutput method. The stream is not opened until getOutputStream is called. At that point a request is made to the caching system, if caching is used that is, to store the page. Some aspects of the caching system are locked while this stream is open. Furthermore, something sensible should be written when started, and that output may be used again from the cache. Thus you should open the stream only when you know that the request is valid and you can output something sensible. The stream also must be properly closed once done. Failing to do so will keep the caching system locked which may in turn lock the whole application.

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.String	cacheKey
private java.util.concurrent.Future	future
private java.io.OutputStream	out
private javax.servlet.http.HttpServletResponse	resp

Constructor Summary

Constructors

Modifier	Constructor and Description
private	OutputProvider(javax.servlet.http.HttpServletResponse resp)
private	OutputProvider(java.io.OutputStream out)
private	OutputProvider(java.lang.String cacheKey)

Method Summary

Modifier and Type	Method and Description
java.util.concurrent.Future	getFuture() Returns a future object representing a returnOutput method call.
java.io.OutputStream	getOutputStream() Opens and returns the output stream where page contents can be written.

Methods inherited from class java.lang.Object

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

Field Detail

cacheKey

private java.lang.String cacheKey

out

private java.io.OutputStream out

resp

private javax.servlet.http.HttpServletResponse resp

future

private java.util.concurrent.Future future

Constructor Detail

OutputProvider

private OutputProvider(javax.servlet.http.HttpServletResponse resp)

OutputProvider

private OutputProvider(java.io.OutputStream out)

OutputProvider

private OutputProvider(java.lang.String cacheKey)

Method Detail

getFuture

public java.util.concurrent.Future getFuture()

Returns a future object representing a returnOutput method call. In case output is written directly into an HTTP response, the whole thing is done with piped input and output streams to avoid buffering all the results. Another thread is created to call the returnOutput method while page contents are written in doOutput. The Future object returned by this method represents the returnOutput call. Calling get method of the Future object will wait for that process to finish. Prior to that, the output stream must be closed, otherwise returnOutput won't know when the end of stream has been reached and the threads will dead lock.

This is all done in the CachedAction implementation of handleAction. Unless you completely circumvent this implementation, you don't need to worry about any of this.

Returns:

A Future object representing an asynchronous returnOutput call if the output is done directly to an HTTP response. Otherwise returns null.

getOutputStream

public java.io.OutputStream getOutputStream()

Opens and returns the output stream where page contents can be written.

Returns:

An OutputStream where to write page contents.