Package org.apache.uima.pear.util

Class MessageRouter

java.lang.Object
org.apache.uima.pear.util.MessageRouter
All Implemented Interfaces:
Runnable
public class MessageRouter extends Object implements Runnable
The MessageRouter class facilitates intra-process message routing. It provides application classes with convenient access to the message channels via the PrintWriter class. The MessageRouter class, by default, defines 2 standard message channels - for standard output and standard error messages. Applications can publish their standard output and standard error messages using the outWriter() and errWriter() methods correspondingly.
The MessageRouter class distributes the messages to a number of message channel listeners, added by applications. Standard message channel listeners should implement the MessageRouter.StdChannelListener interface. The MessageRouter class collects all published messages. When a new message channel listener is added, it receives all collected messages from the message history.

The MessageRouter code runs in a separate thread that should be started and terminated by applications. Applications should use the start() and terminate() methods to start and terminate the MessageRouter thread correspondingly.
For terminology see the Enterprise Integration Patterns book.

  • Constructor Details

    • MessageRouter

      public MessageRouter()
      Default constructor for the MessageRouter class. This constructor allocates all resources, but does not start the main service thread. Applications should start the MessageRouter thread using the start() method.

  • Method Details

    • addChannelListener

      public void addChannelListener(MessageRouter.StdChannelListener listener)
      Adds a given object, implementing the StdChannelListener interface, to the list of standard message channel listeners. Sends to the new listener all previously collected messages for this channel.
      Parameters:
      listener - The given new standard message channel listener.

    • countStdChannelListeners

      public int countStdChannelListeners()
      Returns:
      Current number of standard channel listeners.

    • isRunning

      public boolean isRunning()
      Returns:
      true, if the router thread is running, false otherwise.

    • removeChannelListener

      public void removeChannelListener(MessageRouter.StdChannelListener listener)
      Removes a given StdChannelListener object from the list of standard channel listeners.
      Parameters:
      listener - The StdChannelListener object to be removed from the list.

    • run

      public void run()
      Implements the main service method that runs in a separate thread.
      Specified by:
      run in interface Runnable

    • errWriter

      public PrintWriter errWriter()
      Returns:
      The standard error message channel writer.

    • outWriter

      public PrintWriter outWriter()
      Returns:
      The standard output message channel writer.

    • start

      public void start()
      Starts the main service thread.

    • terminate

      public void terminate()
      Terminates the main service thread.