1. Aaron Zeckoski azeckoski@gmail.com
Tomcat Debugging
Aaron Zeckoski

2. Why bother with a debugger?
Allows tracing of unfamiliar code
Learning process
Reduces the busywork involved with adding in lots of logging
System.out.println
Log.debug
Allows ability to see what is going on in code outside your control

3. Programmers Cafe
Instructions for setting up tomcat debugging are available on the café website

4. Tomcat JPDA Java Platform Debugger Architecture
Tomcat can be configured to allow a program such as eclipse to connect remotely and see debugging information
Simply need to add a command line option
jpda start (possibly debug in older versions)
WIN: set JPDA_ADDRESS=8000
set JPDA_TRANSPORT=dt_socket
bin/catalina.bat jpda start
UNIX: export JPDA_ADDRESS=8000
export JPDA_TRANSPORT=dt_socket
bin/catalina.sh jpda start
URL:

5. Adjusting the tomcat startup script
This is an easy way to always have your server listening for a debugger connection
Add the following environment variables at the beginning of your startup script
Adjust the startup line at the end of the script
set JPDA_ADDRESS=8000
set JPDA_TRANSPORT=dt_socket
WIN: call "%EXECUTABLE%" jpda start %CMD_LINE_ARGS%
UNIX: exec "$PRGDIR"/"$EXECUTABLE" jpda start

6. Configuring eclipse
Eclipse can be configured to provide debugging information for a running tomcat instance that is configured with JPDA support
You will need to have tomcat setup first
URL:

7. Setup Eclipse Tomcat Debugging
Under the "Run" menu, select "Debug…"
Double-click the heading "Remote Java Application“ to create a new configuration
Enter a meaningful name for this configuration
(e.g. sakai_tomcat_debug)
Change to the "Source" tab, then click "Add"
Click "Java Project", then click "OK"
Click "Select All“, then click "OK"
(or check the projects you wish to import)
Click the "Connect" tab and check the box marked "Allow termination of remote JVM"
Click "Apply" to save your changes

8. Using Eclipse to Debug Sakai
Set a breakpoint somewhere in your code (preferably something not associated with startup) by left-clicking to the left of a line of code
Click on the debug icon at the top (looks like a little bug) to start debugging
Might need to click the down arrow and select your sakai debugging config
Click through the app in a browser until your breakpoint is reached
Focus will shift to the debugger automatically

9. Eclipse Debugging Lots of tutorials available online In a nutshell
Use google search!
In a nutshell
create breakpoints
Use the step-into, step-over, etc… to navigate through the code
Use Resume to start running code again
Disconnect to break the debug connection
Stop to shutdown tomcat

10. More tomcat stuff Can redeploy your sakai apps in tomcat
Just run maven sakai from within the tool directory of most any sakai app project
Cannot redeploy the services though
If you run maven sakai from within the service directory or with the root of a project while tomcat is running then Sakai will die horribly
Just restart tomcat and everything will be ok again

11. Windows Webapp redeployment
Windows locks the files and jars in tomcat so that it is difficult to redeploy webapps
Overcome this limitation by adding the antiResourceLocking and antiJARLocking attributes to your base context file context.xml ($CATALINA_HOME/conf/context.xml)
<!-- The contents of this file will be loaded for each web application -->
<Context antiJARLocking="true" antiResourceLocking="true" >
<!-- Default set of monitored resources --> …
URL:

12. Questions?