CODEWITHSUNDEEP
javaeclipsepluginsreflectionclassloader
user2343753
user2343753

Reputation: 41

Class loading in eclipse plugin

I made a eclipse plugin that acts on JavaProject. It needs access to information contained in the bytecode of the classes of the project and, therefore, I used a URLClassLoader (saying to it that the classes are in the "bin" folder of the project) to get the reference to classes and retrieve all the information I need . Unfortunately, when I call the method loadClass("a certain class in JavaProject") I get an error of this type:

org.eclipse.e4.core.di.InjectionException: java.lang.NoClassDefFoundError: javassist/bytecode/BadBytecode

I have found that errors of this kind are due to the fact that external libraries added to the JavaProject's BuildPath are not "known" by the classloader: classes of these libraries are used by JavaProject's classes

In the previous case was used the BadBytecode class of library javassist in this statement of a class of JavaProject

public static void main(String[] args) throws NotFoundException, BadBytecode, IOException, CannotCompileException{

So how do I make my plugin visible to the classes of external libraries imported into the java project?

Upvotes: 4

Views: 1776

Answers (2)

yangyixiaof
yangyixiaof

Reputation: 257

You must get the classloader in the selected java project, then use the classloader to load class. Java project's classloader is different from the classloader in eclipse plugin. see the detail code in the following link: https://sdqweb.ipd.kit.edu/wiki/JDT_Tutorial:_Class_Loading_in_a_running_plugin

Upvotes: 2

Konstantin Komissarchik
Konstantin Komissarchik

Reputation: 29139

You can access Java project's build path by using JavaCore.create( [IProject] ) API which gives you an IJavaProject that has API to traverse the build path. Having said that, you should definitely not be doing this. URLClassLoader has no notion of reloading existing classes, so it would never see updated versions as user edits their code and it has a tendency of locking jar files (such as ones on your build path). JDT has API for safely traversing type structure of the Java Project that doesn't involve using class loaders.

Upvotes: 2

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