Eclipse breakpoint invalid

[gaop818]

I created four maven projects, namely:

project_core, project_a, project_b, project_main.

The relationships are:

project_a relies on project_core,
project_b relies on project_core;
project_main as a startup project, through external configuration files and customized ClassLoader load project_a and project_b, similar to tomcat.
The problem is:

I set up a breakpoint in the project_core, project_a, project_b related classes.

I thought when I start project_main, you can debug project_core, project_a, project_b.

But in project_a, project_b the breakpoint is invalid, only in the project_core my breakpoint works.

I added project_core, project_a, project_b in the project_main debug configurations -> Source Lookup Path.

When the project_main start, how to project_a, project_b debugging ?

[chaarmann]

The problem is that Eclipse cannot find the source code files for the compiled subprojects (class files). For maven there are special jar libraries containing the source code that you should include.
Non-maven: If the jar is in a library, you should see the path to the jar in the package explorer view of eclipse.
View the Properties for the JAR files of your subprojects. You should see where Eclipse gets the source code for classes in the JAR file under Java Source Attachment.
If this doesn't help, ask your question in an Eclipse forum. (You are here in the Java forum.)