(Eclipse) is it possible to dump execution data programatically?

[lufi...@redhat.com]

Hello,

While debugging SWT, I have the situation where I'm interested in what happens during a particular event (e.g low level drawing issues).

Currently I do a Thread...sleep(..) manually dump the execution. Let the event run and at the end I do System.exit(..).
This gives me a picture of what ran during that event.

However, above method is sometimes hard to use with some events. (e.g Drag and Drop debugging).

Is there any way to programatically initiate a "Dump Execution Data" ? (with "reset data" enabled).

Thank you

[Evgeny Mandrikov]

Hi Leo,

First of all - there is extensive documentation covering features of EclEmma ( http://www.eclemma.org/ ) and its underlying coverage engine JaCoCo ( http://www.jacoco.org/jacoco/ ). Please study.

In particular there is documentation about APIs that JaCoCo exposes - http://www.jacoco.org/jacoco/trunk/doc/api/index.html

The interesting part is "JaCoCo Runtime" package "org.jacoco.agent.rt" with description "API to access the JaCoCo agent from within the JVM under test",

which contains class

http://www.jacoco.org/jacoco/trunk/doc/api/org/jacoco/agent/rt/RT.html - "Entry point to access the JaCoCo agent runtime."

that provides access to

http://www.jacoco.org/jacoco/trunk/doc/api/org/jacoco/agent/rt/IAgent.html - "Runtime API and MBean agent interface."

In a usual Java application this can be easily used via reflection, because agent is loaded into application classloader and so application can easily access these classes.

For example to call method "reset" which will clear already collected information:

public class Example {

  public static void main(String[] args) throws Exception {

    Object jacocoAgent = Example.class.getClassLoader().loadClass("org.jacoco.agent.rt.RT").getMethod("getAgent").invoke(null);

    jacocoAgent.getClass().getMethod("reset").invoke(jacocoAgent);

  }

}

But I assume that your tests are executed inside OSGi container? In this case access gets complicated.

Fortunately the exact same API can be exposed via MBean by setting agent option "jmx=true" - see http://www.jacoco.org/jacoco/trunk/doc/agent.html

However EclEmma exposes limited set of agent options and "jmx" is not one of them - see http://www.eclemma.org/userdoc/preferences.html

Luckily there is no validation of properties, so you can abuse a bit e.g. "includes" to set "jmx=true" :

but please don't tell anyone that I recommended to do this ;) :D we state on the same page: "Use these options with caution! Invalid entries might break the code coverage launcher."

For the example - below is screenshot of usage of EclEmma for the one of its own UI tests that use SWTBot and are executed inside OSGi container, pay attention on elements marked as covered:

Now let's add reset via MBean and execute this test again:

As you can see from screenshots: code above "reset" is not considered as covered anymore, as well as creation of "view" that is done by this code, but disposal of "view" is considered as covered because executes after "reset".

Hope this helps.

P.S. please take a bit of time to study documentation.

Regards,

Evgeny

[lufi...@redhat.com]

On Friday, March 16, 2018 at 4:54:07 PM UTC-4, Evgeny Mandrikov wrote:
> Hi Leo,

Thank you very much, exactly what I was looking for :-D.

I updated my blog article and added how to programatically restart code coverage:
https://developers.redhat.com/blog/2017/10/06/java-code-coverage-eclipse/

The api is also quite interesting, thanks for pointing to the relevant sections.

I've been using the above technique to figure out some SWT bugs, very helpful!