Configuration
As stated in the Apache Tomcat documentation, in order to enable remote
debugging support, you'll need to pass the following argument to the JVM
used by Tomcat, when it starts :
-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n
Since Apache has already announced that they'll stop supporting Tomcat 5
soon, therefore I won't address this version of Tomcat's
configuration.
Regarding Tomcat 6 (and later), it already provides all the required configuration in the catalina.bat file
: the default transport type is already set to "dt_socket" (the other
supported transport type is "shared memory" but this one is not commonly
used - actually, I haven't used it so far so I won't be able to tell
you what it is about precisely) and the default port is set to 8000. In
case the port number 8000 is already in use in your environment, you can
simply change it by editing the catalina.bat file.
**
if not ""%1"" == ""jpda"" goto noJpda
set JPDA=jpda
if not "%JPDA_TRANSPORT%" == "" goto gotJpdaTransport
set JPDA_TRANSPORT=dt_socket
:gotJpdaTransport
if not "%JPDA_ADDRESS%" == "" goto gotJpdaAddress
set JPDA_ADDRESS=8000
:gotJpdaAddress
if not "%JPDA_SUSPEND%" == "" goto gotJpdaSuspend
set JPDA_SUSPEND=n
:gotJpdaSuspend
if not "%JPDA_OPTS%" == "" goto gotJpdaOpts
set JPDA_OPTS=-agentlib:jdwp=transport=%JPDA_TRANSPORT%,address=%JPDA_ADDRESS%,server=y,suspend=%JPDA_SUSPEND%
:gotJpdaOpts
shift
:noJpda
Suppose you need to change the default port, you'll, then, set another value to the JPDA_ADDRESS variable.
Running Tomcat with remote debugging enabled
- deploy the application you need to debug as usually
- start Tomcat by executing the catalina.bat script and providing the "jpda" argument
Then, all you need to do is to create a remote Java application in Eclipse through these few steps :
1° Open the debug configurations
3° Specify the project you're debugging (in my example, I've configured
remote debugging for one on my sample projects, named "Blog - Remote
Tomcat debugging")
4° Specify the host on which the application to debug is deployed
5° Specify the port that is opened for debugging purpose (same as the one configured as JPDA_ADDRESS in the catalina.bat file from Tomcat)
6° Launch the Remote application by clicking on "Debug"
At this point, you could set breakpoints wherever you want in the
project's source code and if the code marked with your breakpoints is
executed, the running thread will be suspended and you'll be able to
watch variables' value, execute expression, and so on.
