How can I tell from a JUnit test whether an Eclipse project is open?

I need to run Maven from the command line while Eclipse is open. Since this can confuse Eclipse, I configured the two to use different output folders (Maven writes to target, Eclipse m2e uses target-eclipse). This works very well.

But in one of my unit te开发者_开发知识库sts, I need to load classes which are part of a project but not on the classpath. Basically, I build my own URL classloader. Now, I have a problem: Which class folder to add?

If the project is open, target-eclipse/classes is the correct choice, otherwise I should use target/classes.

Assume that I know the Eclipse folder and the workspace folder. How can I tell from Java code running in a child process of Eclipse (not an Eclipse plugin) which projects are open and which aren't?

The existence of the folder is not a good criteria since the folder isn't deleted when I close a project.

[EDIT] Basically my question is: Eclipse must store that information somewhere in $workspace/.metadata or in $ECLIPSE_HOME/configuration. In which file do I need to look?

A file [Workspace_Home]/.metadata/.lock tells You the workspace is open.

The list and settings of projects in the workspace are in [Workspace_Home]/.metadata/.plugins/org.eclipse.core.resources/.projects.

It seems like open Java projects have a folder [Workspace_Home]/.metadata/.plugins/org.eclipse.core.resources/.projects/[Project_name]/.indexes, and closed don't have it. - I double checked it, and it seems I was wrong here.

But I just checked that closed Java projects have a file: [Workspace_Home]/.metadata/.plugins/org.eclipse.core.resources/.projects/[Project_name]/org.eclipse.jdt.core/state.dat, and open projects don't have it.

I would just use some configuration parameter (a system property for example), telling where the folder is. See http://maven.apache.org/plugins/maven-surefire-plugin/examples/system-properties.html for how to pass system properties when running tests with Maven. The first example in this page shows how to pass the build directory as a system property.