I have an application that I deployed in tomcat. Later I configured the code as a project in Eclipse. I want to connect to the tomcat via eclipse and debug the application. Trying to setup a remote debug connection is throwing up errors. Is there any entry that I need to add somewhere in tomcat?
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8 Answers
First, you need to run Tomcat in debugging mode. The easiest way to do that is to modify the startup file (.bat or .sh depending if you are Windows or not). Find the line near or at the end of the file that contains the start command, and change it to jpda start. This will cause Tomcat to start in debugging mode listening on port 8000.
Next, to connect to this process via Eclipse, select the Run menu and choose Debug Configurations.... In the pane on the left, choose Remote Java Application and click the New launch configuration button above the list. The important settings to note are the Host and Port fields. The host value must match the hostname of the Tomcat process, and the port should be 8000. You also might need to add entries on the Source tab to ensure that all of the source code is available to step through.
5 Comments
user811433
Laz, I did all of this. But am still ending up with the error saying "Failed to connect to remote VM. Connection refused." Any idea why this error comes up?
laz
Sounds like Tomcat isn't listening for whatever reason. Which file did you end up modifying?
user811433
Finally got it working. I added the JVM OPTS explicitly and gave a port other than the default 8000. Was able to get the debug connection working that way. Thanks for the help Laz!
Gopakumar N G
@user811433 How did you add JVM OPTS ? Can you just post your startup.bat in which you added JVM OPTS?
thisdotnull
Finally it worked. Port for debugging is
different from connector port for your app. For some reason I thought that the port had to be 8080 or whatever it is that you are using instead of 8000.- Create a new tomcat server
- Create a new dynamic web project
Export war to tomcat server
- Tomcat debug configuration(important), first double click tomcat server, then select "Use Tomcat installation (takes control of Tomcat installation)"
- Add breakpoints
- Run tomcat in debug mode
- Test war in web browser
- Edit source path
- Debug source code in Tomcat
The war file is available here.
1 Comment
Brent Sandstrom
This is a super useful answer, just not to this question. I learned something, but not the answer to this problem
Simply change the line in startup.bat (if you are using Windows)
from:
call "%EXECUTABLE%" start %CMD_LINE_ARGS%
to:
call "%EXECUTABLE%" jpda start %CMD_LINE_ARGS%
Comments
yes, you need to configure tomcat to accept remote debugging connections. There is a FAQ on how to do it with various IDEs.
https://cwiki.apache.org/confluence/display/TOMCAT/Developing#Developing-Q1
1 Comment
user811433
Thanks for the link. I added the settings and tomcat on startup days "Listening for transport dt_socket at address: 8000". After this I tried Remote debugging from eclipse and it again fails with the same error "Failed to connect to remote VM. Connection refused."
- Right Click on the project you want to debug and go to Debug As Menu and in the list click on Debug Configurations.
Then Double click on the Remote Java Application from left menu list. browse for the project u wanna add in then click apply.
- Also change the listening port to 7999, then after you started the web app from your localhost click the debug button on the same window. Then any break point's will be hit after that.
Comments
Debug worked for me. I was using tomcat 8, configured on centos 7. Debug port opened for me after changing 2 settings.
- Open tomcat/conf/bin/startup.sh and added below lines
export JPDA_ADDRESS=8000
export JPDA_TRANSPORT=dt_socket
- In the same file startup.sh, added jpda before start command.
exec "$PRGDIR"/"$EXECUTABLE" jpda start "$@"
Restart the tomcat. In eclipse go to Run>Debug configuration>Remote java application>Add host ip and port(8000) where tomcat is running. In my case i required to open 8000 through firewall too.
firewall-cmd --zone=public --permanent --add-port=8000/tcp
firewall-cmd --reload
Comments
Steps to setup the tomcat Debugger with eclipse
Install the following things:
java 1.8+
eclipse EE version
download tomcat 8+
open eclipse and go to
serverstab and add a new server(window-> show View-> Others -> Search Servers)Mark your project as Dynamic web Project(Rightclick on Project-> project facets -> select Dynamic web module)
Export war (File-> Export-> search war -> select module and choose the path)
Run as -> Run on Server
Start the tomcat Server in Debug or Run Mode
check on
localhost:8080
Comments
Beside remote debugging, you can debug your app locally within eclipse if you added tomcat in eclipse. just start server and wright click your app and from debug menu hit debug on server. If you have multi module maven project, debug on server just shown up for module with war packaging. If you want debug a class that runs at startup by self, like methods that annotated with @PostConstruct, remember that you should increase server timeout. To do that, go to server view and double click on tomcat and in server preview tab, increase the timeout value.
