Red Hat

Developer Materials

How to Write an Asynchronous Servlet

  • Author:
  • Contributors: Sande Gilda, Pete Muir
  • Last Update: Nov 08, 2013
  • Level: Intermediate
  • Technologies: Servlet, CDI, EJB
  • Target Product: EAP

What is it?

This is a sample project showing the use of asynchronous servlets.

It shows how to detach the execution of a long-running task from the request processing thread, so the thread is free to serve other client requests. The long-running tasks are executed using a dedicated thread pool and create the client response asynchronously.

A long-running task in this context does not refer to a computation intensive task executed on the same machine but could for example be contacting a third-party service that has limited resources or only allows for a limited number of concurrent connections. Moving the calls to this service into a separate and smaller sized thread pool ensures that less threads will be busy interacting with the long-running service and that more requests can be served that do not depend on this service.

System requirements

The application this project produces is designed to be run on Red Hat JBoss Enterprise Application Platform 6.1 or later.

All you need to build this project is Java 6.0 (Java SDK 1.6) or later, Maven 3.0 or later.

Configure Maven

If you have not yet done so, you must Configure Maven before testing the quickstarts.

Start the JBoss Server

  1. Open a command line and navigate to the root of the JBoss server directory.
  2. The following shows the command line to start the server:

     For Linux:   JBOSS_HOME/bin/standalone.sh
     For Windows: JBOSS_HOME\bin\standalone.bat
    

Build and Deploy the Quickstart

NOTE: The following build command assumes you have configured your Maven user settings. If you have not, you must include Maven setting arguments on the command line. See Build and Deploy the Quickstarts for complete instructions and additional options.

  1. Make sure you have started the JBoss Server as described above.
  2. Open a command line and navigate to the root directory of this quickstart.
  3. Type this command to build and deploy the archive:

     mvn clean install jboss-as:deploy
    
  4. This will deploy target/jboss-servlet-async.war to the running instance of the server.

Access the application

The application will be running at the following URL http://localhost:8080/jboss-servlet-async/.

Undeploy the Archive

  1. Make sure you have started the JBoss Server as described above.
  2. Open a command line and navigate to the root directory of this quickstart.
  3. When you are finished testing, type this command to undeploy the archive:

     mvn jboss-as:undeploy
    

Run the Quickstart in JBoss Developer Studio or Eclipse

You can also start the server and deploy the quickstarts from Eclipse using JBoss tools. For more information, see Use JBoss Developer Studio or Eclipse to Run the Quickstarts

Debug the Application

If you want to debug the source code or look at the Javadocs of any library in the project, run either of the following commands to pull them into your local repository. The IDE should then detect them.

    mvn dependency:sources
    mvn dependency:resolve -Dclassifier=javadoc

Recent Changelog

  • Nov 8, 2013(Sande Gilda):Bz1028448 Add spaces to end of metadata so it renders with a line break in HTML
  • Oct 8, 2013(Sande Gilda):BZ1011833 Add HTML versions of README files and fix deployment instructions
  • Oct 2, 2013(Sande Gilda):README add Product Versions metadata remove versions in text remove temp repo from settings.xml
  • Sep 24, 2013(Sande Gilda):Remove references to web profile
  • Sep 24, 2013(Sande Gilda):Remove references to JBoss AS 7 from the quickstarts
  • Sep 23, 2013(Sande Gilda):Update metadata source URLs to new repository
  • Sep 13, 2013(Sande Gilda):JDF 487 Remove as from quickstart artifactId and archive names and access URLs in README files
  • Jun 12, 2013(Sande Gilda):Modify README file internal links to use generated anchors. Remove hard coded anchors. Fixed obsolete links and other markdown rendering problems
  • Feb 12, 2013(Sande Gilda):Add quickstart source repository of record to the README files
  • Sep 11, 2012(Sande Gilda):Add target product https issues.jboss.org browse JDF 108
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