I have a remote server that is running a Java program in debug mode.
It has the following Java opts:
JAVA_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005"
I can successfully connect to it with an IntelliJ Debugger.
I can stop the process from IntelliJ and also get thread dumps.
I would now like to add a breakpoint for a certain method. However, using the Breakpoint window to set i.e. a wildcard match for class pattern and a method name works theoretically, but it is so extremely slow that it’s impossible to use it to debug web requests.
I do have the jar available so I would like IntelliJ to decompile the jar, show it to me as source code and allow me to set breakpoints in the decompiled jar.
How can I achieve this?
(I have full permissions to do this and also the actual source code available, but for legal reasons I cannot transfer the source code to the machine from where I‘m debugging)
Turned out to be fairly simple:
Open the folder with all the jars in IntelliJ (they show as a list but aren’t „browsable“
Right-click the folder, „Open Module Settings“
Go to „Libraries“
Click „+“ and then „Java“
Select all the jars in that directory
Now all the jars are browsable
Set breakpoints in the jar code
I have a java project: simple telegram bot. It worked while I didn't tried deploy it on Heroku. I did a backup for stable version, but Eclipse keeps showing me this ERROR. IDK what's wrong with it, I tried a lot of stuff, like what's the problem? I have src folder, classes also, I have main... Maybe problem in .gitignore file?
But I deleted from it *.class, it's still not working. Help
It's not a duplicate, because I'm workin in Eclipse and it worked earlier. Added my folder properties. I need short answer, not just a wiki of possible problems because it doesnt help.
Folder props
Screenshot error and folders
Your project configuration is very bizarre; you have class files in a directory named 'SRC'. It's hard to tell what you did to manage to create a project def this bizarre. Some ideas:
You've compiled this on the command line. You should probably look into build systems like maven or gradle to build your code. Even if not, use the -d switch on javac to ensure the class files end up in a directory named 'bin' or 'build'.
You've turned off eclipse's autocompile function. Turn it back on.
Right click your Point.java file (not Point.class) and pick 'run...' from the context menu. Assuming autocompile is on this will work.
Generally, use packages. Stuff in the default package is unrunnable in various scenarios. From what I can tell you're not in one of those 'default package is not runnable' scenarios but perhaps I'm missing something.
I wrote a program that spans a few classes in IntelliJ and it works fine when I was testing it in the IDE. However, whenever I follow tutorials to make my project into a .jar executable, it does not run.
The file in the out folder does not run when double-click on it and says "The Java JAR file "projectName.jar" could not be launched.
When opening it from the terminal, I get the error "Could not find or load main class". I used "$ java -jar projectName.jar "
I followed these steps:
Open Project Structure, Artifacts and click the (+).
Under JAR, from modules with dependencies.
Point to the class with my main method and click OK.
Click apply and OK to exit.
Then I close project structure and open Build and then Build Artifacts...
Then I click Build.
Navigate to ~/IdeaProjects/projectName/out/artifacts/projectName_jar/projectName.jar
Then I would try to run it but it does not run. My project has both a GUI and can be run from command lines. When I compiled the main method in Terminal, it worked fine, but I need a JAR file. I'm not sure what I should include in the question, since I'm sure that my code is unrelated. I also utilize Maven, not sure if that is related. Are there other things that I should be doing or adding to my project before I build the JAR?
This can be a result of the Manifest being created in the wrong place.
First make sure it is in src/main/resources/META-INF/MANIFEST.MF
(Intellij sometimes incorrectly places it in /src/main/java/META-INF/MANIFEST.MF)
Then Make sure the jar is looking for META-INF in the src dir NOT in /java OR /resources. This means:
When you set up File>Project Structure>Artifacts>+>JAR>From modules with dependencies... then your Directory for META-INF/MANIFEST.MF should end at src. Example:
ONLY C:\Users\User\StudioProjects\Project\src\
NOT THE PREPOPULATED C:\Users\User\StudioProjects\Project\src\main\java
If your Project Structure jar is already set up change the Manifest File path to:
C:\Users\User\StudioProjects\Project\src\META-INF\MANIFEST.MF
INSTEAD OF C:\Users\User\StudioProjects\Project\src\main\java\META-INF\MANIFEST.MF
You need to make sure that the Main-Class attribute is set. One way to check this is by opening the Jar with a Zip utility and looking for META-MF/MANIFEST.MF extract or open that file with a notepad, notepad++ or any document reader. If "Main-Class" is not in their or set to the correct main class you will received the error you have received. Seeing the IntelliJ tutorial it has a Main-Class field when setting up artifact publishing. I have included the link below to the IntelliJ page.
IntelliJ Creating an Artifact Tutorial
I have a jar file which is having some issue and I would like to debug it.
I created the application on eclipse. During dev phase I have done debug but with the source code. I wanted to debug jar file to find out the reason of error i.e. it could be source code I have is different from jar file or some jar file issue.
Seems like you want to remote debug.
The use this command to launch your jar:
java -Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=y -jar [JAR NAME HERE]
It should state something like :
Listening for transport dt_socket at address : 8001
And in eclipse, create a "Remote Java Application" debug configuration. The configuration is the only thing that matters as long as you have your project of interest open. Add the project[s] of interest that you would like to debug onto your source lookup path and set the port number to the configured address from the java launch command.
When you connect to your debug-enabled jar launch, your jar will halt execution and await debugger input upon hitting breakpoints. Just make sure you have the same version of the code in your jar and your eclipse.
You can use a java decompiler to that effect. I suggest jd (http://jd.benow.ca/).
However, you would also need to include a realign feature (http://mchr3k.github.io/jdeclipse-realign/) for the line numbers to match.
Of course, this can only work if debug information is included in the jar file.
I have no idea why, but from today Eclipse doesn't compile .java files into .class. I press the "Run" button and Eclipse only tries to run the program rather then compiles it first, so i get this error all the time:
Exception in thread "main" java.lang.NoClassDefFoundError
open problems view from window -> show view -> problems, if there's any error, fix it
eclipse will reject to compile if there is any problems in your project
Close Project -> Open Project -> Clean -> Refresh
Hope it helps for someone else
This problem happens when "for some reasons" your project is corrupted and has a red icon near the project's name in Eclipse. The solution is to save the project's folder, delete the project in Eclipse, than create the project again in Eclipse coping all the previous files saved.
I ran into this problem with Eclipse Luna, for some reason the Java builder was missing from the project. Verify that in your .project file you have something like
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
You can also configure builders from Project Properties -> Builders
When I have had this exact same problem, its cause has always been the same and the solution has worked 100% of the time for me. It's caused by a missing jar file in the project's Java build path and it's indicated by a red exclamation point decoration on the project icon. To fix the problem, go to Project|Properties|Java Build Path, click on the Libraries tab and either remove or fix the path for all missing jar files. If your project is configured to rebuild automatically, it should start a build as soon as you apply your changes.
The eclipse needs to erase the output folder when building classes.
The folder is found on Project Properties -> Java Build Path -> Default Output Folder. It can differ from general output folder name found under Eclipse Preferences. If this output folder cannot be erased for some reason (for instance, on Windows, when a shell is opened on this location), the project is marked as corrupted (as Marco Micheli describes) and the classes then are not built.
You just need to make sure the output folder can be erased.
Yes I was facing this issue. Coz Eclipse cannot build the project for Build Path error. Check that your external jar files is not showing any error. Delete the Jar file which one is missing or which one is showing re color. delete that one. add a fresh one from the correct path or location. if all the error are gone. then in the project bin folder one class file will be created and then could not load main class error will be removed too.
there can be errors in your project, or other reasons like mentioned in above answers.
or you may be a fool like me
who moved the source code to other folder and not updated source path in project build properties. in this case it was not giving any error or class files too.
check that too.
goto
Project Properties -> Java Build Path -> Source
Add or Link new source folder location.
Do clean all projects ! This will erase all old class files, so eclipse is forced to generate them again.
Some times jars in the build path might be missing even though we are not using it. Since error is there, java files wont compile into classes.
Can check errors from problems view.
Either remove jars from build path or place the missing jars in the build path.
I had problem in eclipse for load module not found and no class file was getting created.
Solution: Go to Create New Project > Under JRE section Choose Use project Specific JRE.
Now Class files are created.
Please check if all the jars are there in your build path settings.
If any jar is missing this issue might come.
I had this problem, I tried the clean, the build manually, open, closing the project, deleting, and open, etc., nothing works, and after 4 hours I get a workaround what works for me.
Please, Make a RAR, ZIP, or copy from your entire project folder as a backup if it doesn't work and you mess around, OK, now:
Clean the Project. It cleaned all my class files from the output folder, but doesn't generate the class files after the clean with the building (but we already know that)
Delete the project (warning, make sure the Delete contents is not selected or your project will dissapear). For me it says something about that desynchronysation with code mix, and hibernate, blabla)
Close myEclipse
Restart your computer.
Open myEclipse
Import the project with the option "Projects from folder or Archive", not with the "existing projects into workspace" option.
Myeclipse start to build the class files, I don't know why, but works for me, I hope this helps somebody else.
Also ensure that there are no projects with fatal errors (projects with ! symbol over it) in the build path of the project which is not generating classes under the bin directory
Just restart your machine.
Its weird but it helps we had loads of problems this type in our company for unknown yet reason. Always restarting the machine helped.
It was normally encountered while trying to run Junit tests and it could not find a class even when the Run configuration was pointed to /bin.
I encountered a similar problem: previously compiled and running java files couldn't run anymore. Eclipse showed "couldn't find class xxxx". When I checked bin folder, the previous .class files were gone. That's why Eclipse couldn't run the files, NOT because of errors in files. I don't know why it can't just re-compile the file, and why the .class file gone missing in the first place.
But I found a solution:
Simply create a dummy java file in the same package (without doing anything just create), then run it. Then magically all previous .class files came back. And I can run those files as before.
Just Remove Your all Jars (Libraries) from the Build Path and refresh and add all jars and clean and build the project
This is probably a rare event but I declared a servlet with annotations and left off the "/" before the servlet mapping name. I spent over an hour chasing my tail, installing new servers, thinking I might even need to re-install my IDE and it was this simple error! Every time I tried to load any page from my Dynamic Web Project I got a 404 error. I could not even load a plain vanilla html page. There really needs to be better error logging with the IDE and Server interaction as there was zero indication of the error and my servlet was never called at the start of my web app. Hope this helps save someone else some frustration. Always name your servlet with a / slash like /myServlet never just myServlet.
I tried many different potential solutions: cleaning, rebuilding, removing, re importing, Update Maven Project and nothing. I still couldn't run my app from Eclipse. In my case the reason was that I was running Eclipse using openjdk-11 while my project was in Java 8. After I've reconfigured Eclipse to be ran from Java 8 everything started to work (in eclipse.ini).
-vm
/usr/lib/jvm/jdk1.8.0_202/bin
I'll explain my solution to this problem: "eclipse not compiling java files into class files". I'm using Eclipse version '2020-03 (4.15.0)'. I have a project that is dependent on a java project. For the dependent project, I was not able to export a jar file containing the compiles classes and resources. To be more precise, the exported jar file did not contain any class files. The output bin folder for the project is empty after doing a project build. In examining the console output when I tried to build all projects indicated that the build failed because the dependent project was missing. In looking at one of the log outputs, I saw something indicating that the build failed because some eclipse class was missing.
One of the things I tried was to do an eclipse update. Eclipse offered up the list of changes and I tried to apply them, but the update failed. I tried to update several times but they all failed. Looking more carefully at the offered up list of updates I noticed that one of the suggested update involved "deleting" Java Development Tools. That line had an warning indicating that the entire feature could not be deleted due to other dependencies and that only the non dependent features would be deleted. Doesn't that sound suspicious. Why was the update trying to delete Java Development Tools? My speculation is that something got deleted from the Java Development tool that was causing the build process to fail. The missing class I saw earlier also suspiciously sounds like it might be part of the Java Development Tools feature.
So what I did to solve the problem was to reinstall eclipse. I used the eclipse loader application to do the reinstall. (Note, I did not uninstall it first). After the reinstall, the dependent project was able to produce classes, and things once again worked as they should.
I certainly don't know how the eclipse release got into this compromised state, but in my situation the re-install of eclipse was the only way I could find to resolve the problem.
There would be the case : if you have opened project explorer in eclipse then it may not show you classes generated under /**/build/classes, in such case open Navigator view of that project and check build directory under the same project.