/ CARGO, ECLIPSE, MAVEN, TOMCAT

Debugging a Tomcat Application

I primarily develop web applications but have been out of it for a while and needed to look at old code for a reminder. Well here is how I configure a project to debug in tomcat.

There are two parts to debugging the application

  1. Configuring the Maven Cargo plug-in. (Deploys the project to Tomcat with debug args)
  2. Attaching Eclipse to a remote process.

Configure Maven Cargo

Setting Description
${cargo.wait} Setting cargo.wait to true will pause tomcat once it’s started so you can debug
${catalina.home} catalina.home should point to the home folder of tomcat /opt/tomcat/
${project-name} The name of the project and war name. 
<plugin>
    <groupId>org.codehaus.cargo</groupId>
    <artifactId>cargo-maven2-plugin</artifactId>
    <configuration>
        <wait>${cargo.wait}</wait>
        <container>
            <containerId>tomcat6x</containerId>
            <type>installed</type>
            <home>${catalina.home}</home>
        </container>
        <configuration>
            <home>target/tomcat6x</home>
            <properties>
                <!-- Debug Mode On -->
                <cargo.jvmargs>-Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=n -Xms512m -Xmx1024m -XX:MaxPermSize=256m -XX:+UseParNewGC -XX:+UseConcMarkSweepGC</cargo.jvmargs>
                <!-- Debug Mode Off -->
                <!--<cargo.jvmargs>-Xnoagent -Xms512m -Xmx1024m -XX:MaxPermSize=256m -XX:+UseParNewGC -XX:+UseConcMarkSweepGC</cargo.jvmargs>-->
            </properties>
            <deployables>
                <deployable>
                    <location>target/${project-name}.war}</location>
                    <pingURL>http://localhost:8080/${project-name}</pingURL>
                    <properties>
                        <context>${project-name}</context>
                    </properties>
                </deployable>
            </deployables>
        </configuration>
    </configuration>
</plugin>

Attach to Remote Process

Create a new Debug Configuration in Eclipse

  • Click on Run -> Debug Configurations
  • Select Remote Java Application
  • Press the ‘New’ Button
  • Give it a name like ‘MyWebApp’
  • Click Browse to select the Project that has the code you want to debug
  • Make sure the Port matches what was configured in Cargo. In this case port 8787

Putting it Together

To debug just do the following now:

  • From the command line in the project run 
    mvn -Dcargo.wait=true cargo:start
  • From eclipse select Debug - MyWebApp

There you go, the project can now be launched and debugged in tomcat.