newClasspathContainerEntry

Introduction

Setting Java project build path involves setting classpaths of the project which are different from the Java runtime classpath. In JDT classpaths are represented with classpath entries which roughly fall into five kinds: source folder entries, binary library entries, prerequisite project entries, classpath variables, and classpath containers.

Start you eclipse JDT, open a Java project and launch the build path configuration window, and you’ll find all the options enabling you to add/remove all kinds of classpath entries. The frequently used JAVA_HOME system variable (under Windows) can be considered as a classpath variable here. And for a classpath container, hereafter comes more.

Classpath Container

Conceptually it is a data structure which represents a set of tupes with each in the form of . An instance of this data structure can be referenced as an instance of IClasspathEntry which wrapped a unique path of type IPath called a container path. It is noteworthy that all kinds of classpath entries mentioned above are represented by instances of IClasspathEntry within which there is a field called kind identifying the kind of entries. And also, it is noteworthy that an instance of ClasspathContainer is not an instance of IClasspathEntry of kind container. Simply speaking, each instance of IClasspathEntry of kind container references as its member field a container path which uniquely identifies an instance of the data structure mentioned above which contains (or references) a set of instances of ClasspathContainer. Actually, it’s still a little complicated. But that’s it. Below is sketched the relationship.

IClasspathEntry(kind: container)-aContainerPath –> , …}>.

Ways of Creating Classpath Container Entries

The implementation details are more complicated. Class or interfaces involved in include JavaModelManager, JavaCore, IClasspathEntry, ClassContainer, IClassContainerInitializer, and other Java Model classes. The set of tupes of the form of are maintained in JavaModelManager.

Generally, there’re two ways of creating a classpath container entry. The 1st way is to hard code creating instances of ClasspathContainer, and the 2nd way is to create instances of ClasspathContainer via the lazily invoked classpath container initializer which you may define onto the extension point org.eclipse.jdt.core.classpathContainerInitializer.

The hard code way:

// create an instance of IClasspathEntry of kind CPE_CONTAINER
// but ClasspathContainer associated to this entry are not yet defined.
JavaCore.newContainerEntry(..);
…
// Create and set the classpath container
JavaCore.setClasspathContainer(..);
…
// Put container path, containers and projects into hashmaps.
// Invoked in JavaCore.setClasspathContainer(..).
JavaModelManager.containerPut(..)

The initializer way:

// Contribute an extension to the initializer extension point.

When classpath entries contained in containers get resolved, the execution process is:

// Methods resolving classpath entries will get method getClasspathContainer(..) invoked.
JavaCore.getClasspathContainer(..);
…
JavaModelManager.getClasspathContainer(..);
…
// Both ways would get this method invoked.
JavaModelManager.containerGet(..);
…
// The initializer way would get this method invoked,
// within which initializer extension(s) will be lazily invoked.
JavaModelManager.initializeAllContainers(..);
or JavaModelManager.initializeContainer(..);

Resources

1. Setting the Java build path
2. JDT 3.2 Source Codes.
   

Technorati : Eclipse, JDT, classpath, java, plugin