I have a tomcat running after making configuration and when I type jdb in terminal it says initializing. So I like to know
How to attach jdb with tomcat and specify servlet name.
What is the compile option (like in C its eg. -g with gdb) to include debugging symbols when compiling servlet with javac
I have opt/tomcat/apache-tomcat-10.0.10 so I guess Tomcat version is 10
The javac command switch to add all debugging symbols is ... -g. Line numbers and source file names are actually added by default, you only gain information on local variables (see this question).
You can not connect a debugger to a running JVM, unless it was started with the appropriate command line option (see this question).
Tomcat has a helper script bin/catalina.sh that can help you start it with the correct parameters:
catalina.sh jpda start starts Tomcat in the background with debugging enabled. You can connect to it with:
jdb -attach localhost:8000
catalina.sh jpda run works as in the previous case, but in the foreground,
catalina.sh debug starts Tomcat through jdb. You just need to use run to start it.
Once you are connected you can use:
stop in <class id>.<method>
to add break points.
Remark: Both javac and jdb are not often used these days. Most people use tools like Ant, Maven, Gradle, etc. to compile their projects and IDEs to debug the code.
Related
Sometimes I have to deal with an improperly configured Eclipse installation and when I try to run it only the dialog "Java was started but returned exit code shows up without giving me any useful information to trace the actual reason Java failed to start.
What is the best approach to debug this kind of problem?
There are several command-line options that can help with troubleshooting. I'd start with -debug -consoleLog and see if that produces useful output.
You can run eclipse with the verbose attribute from command line
eclipse -verbose
Read more about debugging eclipse and plugins here http://exploreeclipse.blogspot.nl/2014/01/enable-eclipse-verbose-for-trouble.html?m=1
By default, eclipse launches with javaw.exe process, since it's a window thread so you will not be able to see any verbose messages.
Step 1: Add below VM parameter in eclipse.ini file. By default, eclipse will have javaw.exe, modify it to java.exe
-vm
C:/KK/jdk1.6.0_32/bin/java.exe
Step 2: Pass verbose parameter during the eclipse launch.
eclipse -verbose
Im trying to enable remote debugging for an eclipse plugin project, for the purpose of using IntelliJ IDEA as a debugger.
The steps I've taken so far:
Launch Eclipse.
Run -> Debug Configurations...
Create a new "Eclipse Application" (as to launch a local workspace which loads the plugin).
Add -Xdebug -Xrunjdwp:transport=dt_socket,address=1044,server=y,suspend=n to VM arguments.
Press the Debug button.
I get the following error:
ERROR: Cannot load this JVM TI agent twice, check your java command line for duplicate jdwp options.
Error occurred during initialization of VM
agent library failed to init: jdwp
What steps should I be taking to get IntelliJ IDEA to be able to debug an Eclipse Plugin running in a runtime workspace?
Run -> Debug Configurations...
Add -Xdebug -Xrunjdwp:transport= dt_socket,address=1044,server=y,suspend=n to VM arguments.
This is redundant. Using a debug configuration already starts the application with the eclipse debugger attached to the process. Start it as a run configuration instead if you want to enable debugging through a server socket.
You can then create an additional "remote java application" debug configuration to attach to that socket.
I would suggest you NOT try to launch the Eclipse app from within Eclipse.
Export the app to be a stand alone eclipse application.
Modify the eclipse.ini file and add the necessary debug parameters to the '-vmargs' entry.
Launch the stand alone app as you normally would.
Attach the development Eclipse instance to the test app as you would normally do for a remote debug.
Tomcat Configuration:->
By default remote debug happens at 8000 port.If you want to change this then go to catalina.bat file and update this line
set JPDA_ADDRESS=localhost:8000 to desired port no.
And you can also set this property in setenv.bat file. Generally this file is not there in tomcat so just create one batch file with name
setenv and write this line set JPDA_ADDRESS=localhost:8000.
Now go to bin directory then open command promt and write "catalina jpda start". It will make the tomcat run in debug mode. You can verify it
by seeing something like this "Listening for transport dt_socket at address: 8000"
1)Eclipse
Go to run->debug configuration->Remote Java Application->Click on new Launch configuration
And then fill the detials like project ,port(Give same port no as you have configured in tomcat), host(If you are using local you can give
local then apply and debug
I am using eclipse 2020.09 .
Eclipse remote debug img
2)Intellij Idea:
Go to Add configuration->click on +->and select remote jvm debug->Then give the same port no and name(any name) then apply.
Intellij Idea Remote Debug img
The problem:
Debugging a java web application deployed in Tomcat 7 is not working. Eclipse seems to connect to Tomcat but breakpoints are ignored when I try to debug. I did the following:
First of all I have also tried: Remote debugging Tomcat with Eclipse.
started Tomcat7 in debug mode with :
set JPDA_OPTS=-agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=n
catalina.bat jpda start
Debug as - > Remote Java Application with host : localhost and port : 8000.
Created a few breakpoints on a servlet where the request should suspend and let me debug but it's like there is no breakpoint set.
Thank you all,
Daniel
P.S. This is my first question so please be kind .
One possible explanation is that the class files in your WAR file (deployed on Tomcat) do not contain line numbers.
If you told us with which compiler and compiler plugin (Oracle javac, Eclipse, ANT, Maven, etc.) the class files were produced and what settings were used we may be able to provide further details.
Update
Author says in comment that ANT is used to compile. Follow-up:
The ANT javac task is just a wrapper around a concrete compiler. So, the options you can set depend on the actual javac. However, what you're looking for is debug="true" debuglevel="lines". ANT will then pass -g:lines to javac (see docs).
Sidenote: optimize="true" is ignored (check the docs).
Does anyone know how to make eclipse or netbeans use the graphics card in optimus laptops by invoking optirun (bumblebee) inside the IDE so that one can just use the run button in the IDE to run the program in a graphics card within the IDE.
In simplest form I just want the IDE to do the equivalent of optirun ./javaproject
The way I did this in Eclipse was to first start the Java debugger jdwp and listen to a port. Then start the JVM with optirun java ... and use jdwp to connect to this port. Both tasks can be started at the same time in Eclipse by creating a Launch Group in the debug configuration settings (Run -> Debug Configurations). In detail:
Create a Remote Java Application debug configuration with "Standard (Socket Listen)" Connection Type and some arbitrary port, e.g. 56789. This attaches the Java debugger jdwp on port 56789 to a virtual machine which accepts debug connections at this port.
Now we need to start a JVM with optirun. This can be done with a External Tool Configuration (Run -> External Tools -> External Tool Configurations). Create a new Program configuration in the left side of the External Tools Configurations window. You could directly start optirun java <additional arguments> by filling in the required fields. However, I have decided to use a shell script which is reusable by different projects (As can be seen below, there is one part missing to make it entirely reusable. I'm glad for any help from more experienced Eclipse users...). Hence, the Location field points to this shell script. The script itself accepts three arguments: the classpath for the project, the name of the Java executable, and the port number. These arguments can be passed to the script in the Arguments field of the Main tab, e.g.
${project_classpath:${selected_resource_name}}
ExecName
56789
The shell script looks like this, assuming optirun is in your PATH:
#!/bin/sh
CLASS_PATH=${1}
JAVA_EXECUTABLE=${2}
PORT=${3}
# TODO: fix this java library path: pass it as an argument as well. Is there an Eclipse variable which stores this?
JAVA_LIBRARY_PATH=/usr/local/share/OpenCV/java
#------------------------------------------------------------------------------
optirun ${JAVA_BIN} -agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:${PORT} -Djava.library.path=${JAVA_LIBRARY_PATH} -Dfile.encoding=UTF-8 -classpath ${CLASS_PATH} ${JAVA_EXECUTABLE}
#------------------------------------------------------------------------------
Finally, the two pieces are brought together in a Launch Group in the Debug Configurations window (Run -> Debug Configurations). Create a new Launch Group and add the two previously generated Debug configurations by clicking on Add in the Launches tab and by selecting the appropriate configurations.
Note that due to the classpath variable in step 2 (i.e. ${project_classpath:${selected_resource_name}}), the appropriate package needs to be selected in the Package Explorer before clicking on the run debug configuration button (make sure that the Launch Group is selected).
This solution works perfectly for me: I can debug Java code inside Eclipse which calls native code involving CUDA optimizations and Bumblebee only activates the discrete graphics card when necessary.
Just use optirun to start the IDE. For example, optirun eclipse or optirun netbeans
I build the project in Netbeans (F11) and run the following in a terminal:
optirun java -jar path/to/javaproject/dist/javaproject.jar
Mind that if you have any java parameters in your project, you need to add it manually. My workflow is like this:
Locate the Java options from the project, open Project -> Properties, Run. At VM Options I see -Djava.library.path=lwjgl/native/windows;:lwjgl/native/linux. I also have some parameters that I want to pass to main(String[]). With this information, I open a terminal and run:
cd path/to/javaproject
optirun java -Djava.library.path=lwjgl/native/windows;:lwjgl/native/linux \
-jar dist/javaproject.jar some paremeters
Another hint, if you have to open and close the program frequently, run optirun bash in a different tab so that preparing the use of the graphics card becomes faster. Alternatively, you can run optirun netbeans, but that means that the nvidia card will always be on even if you are programming which increases power use and increase the heat.
Important: if you are using a 32-bit JVM or Java libraries on a 64-bit machine, you also need to install the 32-bit drivers and libraries. For Ubuntu, the nvidia package already contains 32-bit drivers, see this answer. For other distros, you likely need to install lib32-* packages for Mesa, VirtualGL and nvidia-utils.
You can also rename java to java_real and use this portion of code as your java command :
#!/bin/bash
path=$(dirname $(readlink -f $0))
args=""
runner="$path/java_real"
for var in "$#"
do
if [ "$var" = "-3d" ]; then
runner="primusrun $runner"
else
args="$args $var"
fi
done
$runner $args
NOTE : I had to do this in /usr/lib/jvm/java-7-openjdk-amd64/jre/bin, not in /usr/bin to make it work with Eclipse.
In Eclipse, just add "-3d" in your program arguments and you're good to go !
Is it possible to launch a debugger such as jdb from Maven? I have a pom.xml file that compiles the project successfully. However, the program hangs somewhere and I would really like to launch jdb or an equivalent debugger to see what's happening.
I compile using mvn compile and launch using:
mvn exec:java -Dexec.mainClass="com.mycompany.app.App"
I was expecting something like:
mvn exec:jdb -Dexec.mainClass="com.mycompany.app.App"
to launch the debugger but, as usual, my expectations are incongruent with maven's philosophy.
Also, I couldn't find any documentation (on Maven's website or google) to describe how debugging works. I suspect that I have to use some plugin.
If you are using Maven 2.0.8+, run the mvnDebug command in place of mvn and attach a debugger on port 8000.
For Maven <2.0.8, uncomment the following line in your %M2_HOME%/bin/mvn.bat (and maybe save the modified version as mvnDebug.bat):
#REM set MAVEN_OPTS=-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
More details in MNG-2105 and Dealing with Eclipse-based IDE.
Just as Brian said, you can use remote debugging:
mvn exec:exec -Dexec.executable="java" -Dexec.args="-classpath %classpath -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=1044 com.mycompany.app.App"
Then in your eclipse, you can use remote debugging and attach the debugger to localhost:1044.
I thought I would expand on these answers for OSX and Linux folks (not that they need it):
I prefer to use mvnDebug too. But after OSX maverick destroyed my Java dev environment, I am starting from scratch and stubbled upon this post, and thought I would add to it.
$ mvnDebug vertx:runMod
-bash: mvnDebug: command not found
DOH! I have not set it up on this box after the new SSD drive and/or the reset of everything Java when I installed Maverick.
I use a package manager for OSX and Linux so I have no idea where mvn really lives.
(I know for brief periods of time.. thanks brew.. I like that I don't know this.)
Let's see:
$ which mvn
/usr/local/bin/mvn
There you are... you little b#stard.
Now where did you get installed to:
$ ls -l /usr/local/bin/mvn
lrwxr-xr-x 1 root wheel 39 Oct 31 13:00 /
/usr/local/bin/mvn -> /usr/local/Cellar/maven30/3.0.5/bin/mvn
Aha! So you got installed in /usr/local/Cellar/maven30/3.0.5/bin/mvn.
You cheeky little build tool. No doubt by homebrew...
Do you have your little buddy mvnDebug with you?
$ ls /usr/local/Cellar/maven30/3.0.5/bin/mvnDebug
/usr/local/Cellar/maven30/3.0.5/bin/mvnDebug
Good. Good. Very good. All going as planned.
Now move that little b#stard where I can remember him more easily.
$ ln -s /usr/local/Cellar/maven30/3.0.5/bin/mvnDebug /usr/local/bin/mvnDebug
ln: /usr/local/bin/mvnDebug: Permission denied
Darn you computer... You will submit to my will. Do you know who I am? I am SUDO! BOW!
$ sudo ln -s /usr/local/Cellar/maven30/3.0.5/bin/mvnDebug /usr/local/bin/mvnDebug
Now I can use it from Eclipse (but why would I do that when I have IntelliJ!!!!)
$ mvnDebug vertx:runMod
Preparing to Execute Maven in Debug Mode
Listening for transport dt_socket at address: 8000
Internally mvnDebug uses this:
MAVEN_DEBUG_OPTS="-Xdebug -Xnoagent -Djava.compiler=NONE \
-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000"
So you could modify it (I usually debug on port 9090).
This blog explains how to setup Eclipse remote debugging (shudder)
http://javarevisited.blogspot.com/2011/02/how-to-setup-remote-debugging-in.html
Ditto Netbeans
https://blogs.oracle.com/atishay/entry/use_netbeans_to_debug_a
Ditto IntelliJ
http://www.jetbrains.com/idea/webhelp/run-debug-configuration-remote.html
Here is some good docs on the -Xdebug command in general.
http://docs.oracle.com/cd/E13150_01/jrockit_jvm/jrockit/jrdocs/refman/optionX.html
"-Xdebug enables debugging capabilities in the JVM which are used by the Java Virtual Machine Tools Interface (JVMTI). JVMTI is a low-level debugging interface used by debuggers and profiling tools. With it, you can inspect the state and control the execution of applications running in the JVM."
"The subset of JVMTI that is most typically used by profilers is always available. However, the functionality used by debuggers to be able to step through the code and set breakpoints has some overhead associated with it and is not always available. To enable this functionality you must use the -Xdebug option."
-Xrunjdwp:transport=dt_socket,server=y,suspend=n myApp
Check out the docs on -Xrunjdwp too. You can enable it only when a certain exception is thrown for example. You can start it up suspended or running. Anyway.. I digress.
I found an easy way to do this -
Just enter a command like this -
>mvn -Dtest=TestClassName#methodname -Dmaven.surefire.debug test
It will start listening to 5005 port. Now just create a remote debugging in Eclipse through Debug Configurations for localhost(any host) and port 5005.
Source - https://doc.nuxeo.com/display/CORG/How+to+Debug+a+Test+Run+with+Maven
If you are using Netbeans, there is a nice shortcut to this.
Just define a goal exec:java and add the property jpda.listen=maven
Tested on Netbeans 7.3
If you don't want to be IDE dependent and want to work directly with the command line, you can use 'jdb' (Java Debugger)
As mentioned by Samuel with small modification (set suspend=y instead of suspend=n, y means yes which suspends the program and not run it so you that can set breakpoints to debug it, if suspend=n means it may run the program to completion before you can even debug it)
On the directory which contains your pom.xml, execute:
mvn exec:exec -Dexec.executable="java" -Dexec.args="-classpath %classpath -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=1044 com.mycompany.app.App"
Then, open up a new terminal and execute:
jdb -attach 1044
You can then use jdb to debug your program!=)
Sources:
Java jdb remote debugging command line tool
Why not use the JPDA and attach to the launched process from a separate debugger process ? You should be able to specify the appropriate options in Maven to launch your process with the debugging hooks enabled. This article has more information.
I use the MAVEN_OPTS option, and find it useful to set suspend to "suspend=y" as my exec:java programs tend to be small generators which are finished before I have manage to attach a debugger.... :) With suspend on it will wait for a debugger to attach before proceding.
I couldn't make any of the other solutions work and then I tried starting maven with the following.
mvn exec:exec -Dexec.executable="java" -Dexec.args="-classpath %classpath -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000 com.example.Main"
This worked for me and then I searched some more and found this other answer. IntelliJ can run Maven project in debug mode but ignores breakpoints
The fact is that my application is a spring-boot application. Now, the link referred to above may be right and the problem is that the spring-boot plugin creates a new fork that somehow invalidates the interaction between debugger and target app. I'm saying this because I got some info on how this may work from here
In any case, I don't know how the two solutions are related to each other. Is the first solution also preventing spring-boot from creating a fork??
Sadly I have no clue at the moment.
Here is how I do it.
For example:
mvn clean azure-functions:run -DenableDebug
Then, after it starts up, you'll see a link in the Terminal that says "Attach Debugger".
To me, that is the easiest way to do it.