IntelliJ IDEA 13 debugger don't stop on breakpoint in java for maven project

Question

I have a breakpoint on a line where is the System.out.println("test") command. I believe that the command is reached by execution because I see the printed string "test". But the breakpoint is ignored.

Breakpoint is a red circle all the time, without a tick or cross. I think this is an issue when IDEA thinks the class is not loaded, while it is, because the command is executed.

I can reproduce it in various circumstances:

1. When I press debug (with maven configuration install exec:exec -DforkMode=never)

2. Remote debugging - I run maven goal in debug mode in the console:

   mvnDebug install exec:exec -DforkMode=never

   or

   mvnDebug install exec:exec

   remote debug configuration in IDEA:

   • Arguments for running remote JVM:
     -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000
   • For JDK 1.4.X:
     -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
   • Transport: Socket
   • Debugger mode: Attach
   • Host: localhost
   • Port: 8000

In both cases the debugger only prints "Connected to the target VM, address: 'localhost:8000', transport: 'socket'"

I have also tried File > Invalidate Caches / Restart and clean build, but the breakpoint is still ignored.

Configuration:

Ubuntu 13.10
IntelliJ IDEA Ultimate build 133.944
Apache Maven 3.0.4
Java version: 1.7.0_51, vendor: Oracle Corporation
OS name: "linux", version: "3.11.0-17-generic", arch: "amd64", family: "unix"

EDIT: relevant part of pom.xml:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>1.2.1</version>
  <configuration>
    <executable>java</executable>
      <arguments>
        <argument>-D--secret--.server.configuration=/usr/local/etc</argument>
        <argument>-classpath</argument><classpath/>
        <argument>com.--secret--.Server</argument>
      </arguments>
  </configuration>
</plugin>

Answer 1

Update 2021:

Nowadays, on most situations, debugging should work out of the box.

Newer versions of IntelliJ IDEA (tested with 2020.3) can now auto-detect maven exec configurations and add the proper options to enable debugging. See IDEA-189973 for further info. Thanks @Gili for opening a ticket for this functionality back in 2018.

Nevertheless my original answer bellow can still be useful for older versions of IntelliJ, Remote Debugging or to debug while using certain Maven / Gradle plugins that Fork the VM and require debugging options to be manually passed downstream (adjust configuration accordingly).

---

My solution:

Considering that you have a program that depends on system properties:

package com.mycompany.app;


public class App {

    private static final String GREETING = System.getProperty("greeting", "Hi");

    public static void main(String[] args) {
        int x = 10;
        System.out.println(GREETING);
    }
}

And you are running it with exec:exec:

mvn exec:exec -Dexec.executable=java "-Dexec.args=-classpath %classpath -Dgreeting=\"Hello\" com.mycompany.app.App"

With some "inception magic" we can debug the process started by Mavenexec:exec.

Maven

Change your exec:exec goal to enable remote debugging. I'm using suspend=y and server=n, but feel free to configure the JDWP Agent as you please:

-agentlib:jdwp=transport=dt_socket,server=n,address=127.0.0.1:8000,suspend=y`

This will not be passed directly to the maven JVM, instead it will be passed to exec.args which will be used by exec:exec:

mvn exec:exec -Dexec.executable=java "-Dexec.args=-classpath %classpath -agentlib:jdwp=transport=dt_socket,server=n,address=127.0.0.1:8000,suspend=y -Dgreeting=\"Hello\" com.mycompany.app.App"

IntelliJ IDEA

Create a Remote configuration (again I'm using a Listen strategy. You should adjust it accordingly):

Now toggle your breakpoints and Debug your remote configuration. Using the settings above it will wait until your process starts:

Finally run the exec:exec line above and debug your application at will:

---

So basically you need two "Run/Debug" configurations for this to work:

1. A Maven configuration for exec:exec with the system properties and JDWP agent configuration:

2. The remote configuration acting as a client.