使用另一个OSGi捆绑包中的类

Question

I'm running in a strange issue with OSGi bundle.

I've got two bundle, let's say B1 and B2 . B1 export the package abc which contain a class name Foo with a method:

public JsonNode helloWorld() {
    System.out.println("Hello World!");
    return null;
}

Then B2 import B1 package and try to use the class Foo from B1 . I have no problem at compilation, neither when starting the bundle in Felix, everything seem to work fine.

BUT when B2 is call to use the helloWorld method, B2 stop working and do not throw any error ! After some debug I figure the return type of the method helloWorld is the cause, if I change JsonNode to String everything work as expected.

Why I haven't error in my felix console ? Why I can't call the helloWorld method when the return type is JsonNode ?

Thanks for help !

Edit1: More information, the following method does the exact same bug:

 public String helloWorld() {
     System.out.println("Hello World!");
     JsonNode test =  JsonNodeFactory.instance.objectNode();
     return test.asText();
 }

I see in the console the Hello World! Then nothing, no error, no trace, just like if the program choose to stop here and wait !

Edit2: I have this warning when building, I don't know if it's important:

 
 
 
 
  
  
  [WARNING] Bundle fr.aaa.ccc.bbbb:1.0.0 : Export javax.json, has 1, private references [javax.json.stream],
 
 
  

Warning remove, still got the same comportement.

Edit3: I manage to get an error in my console and I think i'm closed to find out what's the problem !!!

Caused by: java.lang.LinkageError: 
loader constraint violation: 
when resolving interface method "a.b.c.FooInterface.welcome(Ljava/lang/String;)Lorg/codehaus/jackson/JsonNode;"
the class loader (instance of org/apache/felix/framework/BundleWiringImpl$BundleClassLoaderJava5) 
of the current class, d/e/f/lasthope/Activator, 
and the class loader (instance of org/apache/felix/framework/BundleWiringImpl$BundleClassLoaderJava5) for the method's defining class, a/b/c/aa/bb/FooInterface,
have different Class objects for the type org/codehaus/jackson/JsonNode used in the signature
    at d.e.f.Activator.start(Activator.java:37)

Answer 1

I guess you call the method in a BundleActivator. A common problem there is that exceptions in eg the start method are not logged. So try to use try catch around the call to helloworld and print or log the exception.

I think the problem with JsonNode is that bundle B2 does not see the class or B1 sees a different class. Make sure that both bundles import the package JsonNode is in.