edu.ucsb.adl.middleware
Class CacheLoaderThread

java.lang.Object
  |
  +--java.lang.Thread
        |
        +--edu.ucsb.adl.middleware.CacheLoaderThread

All Implemented Interfaces:

java.lang.Runnable

public final class CacheLoaderThread

extends java.lang.Thread

Background thread that preloads a metadata cache.

This class is implemented as a kind of macro on top of the identifiers and metadata middleware services. As such, it suffers from three limitations:

• The middleware services go through the usual permission checking, using the servlet request object from the invocation of the cache_control servlet. Ideally, permission would be checked only by the servlet, and service-level permission checking would be bypassed.
• The middleware services may write invocation records to log files, which is probably not desirable.
• Most significantly, the thread maintains references to the middleware services, which means they can't be unloaded while the thread is running.

Put another way, the fact that limitations such as the above arise can be seen as a limitation of the middleware architecture as a whole.

Version:

$Header: /export/home/gjanee/middleware/edu/ucsb/adl/middleware/RCS/CacheLoaderThread.java,v 1.1 2006/06/30 06:45:51 gjanee Exp $

$Log: CacheLoaderThread.java,v $ Revision 1.1 2006/06/30 06:45:51 gjanee Initial revision

Author:

Greg Janée
Alexandria Digital Library

Field Summary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

CacheLoaderThread(edu.ucsb.adl.middleware.Global global, javax.servlet.ServletRequest request, java.lang.String collection, java.lang.String view, java.lang.String cacheDirectory)
Creates the thread.

Method Summary

java.lang.String	getCollection() Returns the collection the thread is operating on.
java.lang.String	getException() Returns the exception that prematurely terminated the thread's processing.
java.lang.String	getStatus() Returns the thread's current state.
java.lang.String	getView() Returns the metadata view the thread is operating on.
void	run()
void	stopASAP() Requests that the thread stop as soon as possible.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getContextClassLoader, getName, getPriority, getThreadGroup, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setName, setPriority, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Constructor Detail

CacheLoaderThread

public CacheLoaderThread(edu.ucsb.adl.middleware.Global global,
                         javax.servlet.ServletRequest request,
                         java.lang.String collection,
                         java.lang.String view,
                         java.lang.String cacheDirectory)
                  throws InternalErrorException

Creates the thread.

Parameters:

global - The global object representing this instance of the middleware.

request - The servlet request to use to invoke the middleware services.

collection - The collection, e.g., "adl_catalog".

view - The metadata view, e.g., "adl:bucket".

cacheDirectory - The cache directory pathname.

Throws:

InternalErrorException - If any error occurs.

Method Detail

stopASAP

public void stopASAP()

Requests that the thread stop as soon as possible.

getStatus

public java.lang.String getStatus()

Returns the thread's current state. This method may be invoked even after the thread has finished.

Returns:

The current state.

getCollection

public java.lang.String getCollection()

Returns the collection the thread is operating on. This method may be invoked even after the thread has finished.

Returns:

The collection.

getView

public java.lang.String getView()

Returns the metadata view the thread is operating on. This method may be invoked even after the thread has finished.

Returns:

The view.

getException

public java.lang.String getException()

Returns the exception that prematurely terminated the thread's processing. This method may be invoked even after the thread has finished.

Returns:

The exception, or null.

run

public void run()

Specified by:

run in interface java.lang.Runnable

Overrides:

run in class java.lang.Thread