Eclipse - Unable to install breakpoint due to missing line number attributes

Question

I had the same error message in Eclipse 3.4.1, SUN JVM1.6.0_07 connected to Tomcat 6.0 (running in debug-mode on a different machine, Sun JVM1.6.0_16, the debug connection did work correctly).

Window --> Preferences --> Java --> Compiler --> Classfile Generation: "add line number attributes to generated class file" was checked. I did a clean, recompile. I did uncheck it, recompile, check it, recompile. I made sure the project did use the global settings. Still the same message.

I switched to ant build, using

<javac srcdir="./src/java" destdir="./bin" debug="true">

Still, same message.

I didn't find out what caused this message and why it wouldn't go away. Though it seemed to have something to do with the running Tomcat debug session: when disconnected, recompiling solves the issue. But on connecting the debugger to Tomcat or on setting new breakpoints during a connected debug session, it appeared again.

However, it turned out the message was wrong: I was indeed able to debug and set breakpoints, both before and during debugging (javap -l did show line numbers, too). So just ignore it :)

1. In eclipse menu, go to Window->Preferences->Java->Compiler
2. Unmark checkbox "Add line number attributes..."
3. Click Apply -> Yes
4. Mark checkbox "Add line number attribute..."
5. Apply again.
6. Go happy debugging

This fixed my issue:

1. Window -> preferences -> server -> runtime environments
2. Apache Tomcat -> edit
3. Select a JDK instead of JRE

For Spring related issues consider that in some cases it generate classes "without line numbers"; for example a @Service annotated class without an interface, add the interface and you can debug. see here for a complete example.

@Service("SkillService")
public class TestServiceWithoutInterface {
   public void doSomething() {
      System.out.println("Hello TestServiceWithoutInterface");
   }
}

The service above will have an interface generated by spring causing "missing line numbers". Adding a real interface solve the generation problem:

public interface TestService {
    void doSomething();
}

@Service("SkillService")
public class TestServiceImpl implements TestService {
   public void doSomething() {
      System.out.println("Hello TestServiceImpl");
   }
}