threads in a servlet Google appengine Java (for serializing data from XML to blob, pipedinput, pipedoutput)

Question

How does one know when a Thread one started in a Google Appengine
servlet has completed its assigned tasks.

I am using pipedinput and pipedoutput to get information put XML
into a Blob. That is the XML Serializer outputs to one end of the pipe.
A thread reads the other end of the pipe and puts data into the Blob.

I know that one must use the ThreadFactory, newThread function to activate the thread One cannot use the standard technique from Java of calling Thread.start() .

T TT;
TT = new T();
java.util.concurrent.ThreadFactory TF;
TF = com.google.appengine.api.ThreadManager.currentRequestThreadFactory();
TF.newThread(TT);

Here is how I declare and create my Runnable:

class T implements Runnable {
public void run(){
FileWriteChannel writeChannel=null;
try {

Here is the code to create the Thread. Note that when I declare type T to implement the Thread, I get the security exception below:

class T implements Runnable {
public void run(){
FileWriteChannel writeChannel=null;
try {
...

If I start up a class that extends Thread, Google Appengine gives me run time error.
If I do a "implements" runnable, that is TT in the example above, is an instance
of an ojbect thwt inmpelements Thread, then, I do not have access to the join
capability, which is defined in the Thread class, but not the runnable.

Thread Error java.security.AccessControlException: access denied
("java.lang.RuntimePermission" "modifyThreadGroup")     at
java.security.AccessControlContext.checkPermission(AccessControlContext.java:375)
    at
java.security.AccessController.checkPermission(AccessController.java:565)
    at
java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
    at


com.google.apphosting.runtime.security.CustomSecurityManager.checkPermission(CustomSecurityManager.java:56)
    at
com.google.apphosting.runtime.security.CustomSecurityManager.checkAccess(CustomSecurityManager.java:131)
    at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)*

I am doing the read from the PipedInputStream in a separate thread because
of the statement in the API documentation for PipedInputStream:

"A piped input stream should be connected to a piped output stream; the piped input
stream then provides whatever data bytes are written to the piped output stream.
Typically, data is read from a PipedInputStream object by one thread and data is
written to the corresponding PipedOutputStream by some other thread.
Attempting to use both objects from a single thread is not recommended,
as it may deadlock the thread. "

Dr. Laurence Leff Associate Professor of Computer Science,
Western Illinois University, Macomb IL 61455 on sabbatical

Answer 1

You actually get a Thread from TF.newThread(TT) . Try calling join() on it. Try this:

Thread myThread= TF.newThread(TT);
myThread.join();

Also note: currentRequestThreadFactory() creates threads scoped to the current request. Side effects of such threads is that they cannot outlive request as docs state :

Returns a ThreadFactory that will create threads scoped to the current request. These threads will be interrupted at the end of the current request and must complete within the request deadline.