jython-users

[Jython-users] Threads:-java.lang.ExceptionInInitializationError:java.lang.NullPointerException

[rohit s. <ro2...@ya...>]

I am getting
"java.lang.ExceptionInInitializationError:
java.lang.NullPointerException
at
org.Python.core.PySystemState.<init>(PySystemState.java:158)
at
org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:67)
at
org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:45)
at PyFactory.initialize(PyFactory.java 9)
at A.run(A.java 9)

The classes I am using are as follows(I have included
only the required portion of the code):-

CLASS A:-

import java.util.*;
public class A extends Thread{
  public A(){
  }
  public void run(){
    try{
      synchronized(this){
        PyFactory.initialize();
	PyFactory.getInterp().execfile("Python1.py");
	PyFactory.getInterp().execfile("Python2.ghs");
      }
    }catch(Exception e){
      System.out.println("Exception1"+e);
      e.printStackTrace();
    }
  }
}

CLASS B:-

import java.util.*;
public class B{
   public static void main(String args[]){
	A1 a1=new A1();
	A1 a2=new A1();
	a1.start();
	a2.start();
   }
}

PyFactory.java:-

public class PyFactory{
  private static PythonInterpreter pyInterp;
  public static void initialize() throws
ClassNotFoundException{
    pyInterp=new PythonInterpreter();
  }
  public static PythonInterpreter getInterp(){
    return pyInterp;
  }
}

Python1.py:-

class ExecPython1:
  def __init__(self,b):
    self.test(b)
  def test(self,b):
    a="This is a test"
    print a
    print b

Python2.ghs:-

ExecPython1(1)

Pl explain the cause of the error. When I am creating
and running only one thread then it works fine. But
with more than one threads, it gives this exception.

Pl help!!!!
I am sinking!!!
Thanx in Advance!
Rohit

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Re: [Jython-users] Threads:-java.lang.ExceptionInInitializationError:java.lang.NullPointerException

[<bc...@wo...>]

[rohit seth]

>I am getting
>"java.lang.ExceptionInInitializationError:
>java.lang.NullPointerException
>at
>org.Python.core.PySystemState.<init>(PySystemState.java:158)
>at
>org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:67)
>at
>org.Python.util.PythonInterpreter.<init>(PythonInterpreter.java:45)
>at PyFactory.initialize(PyFactory.java 9)
>at A.run(A.java 9)
>
>The classes I am using are as follows(I have included
>only the required portion of the code):-

[A very good example snipped. This kind of bugs can be hell to track
down, but with your example it was very easy. Thanks]

>Pl explain the cause of the error. When I am creating
>and running only one thread then it works fine. But
>with more than one threads, it gives this exception.

As you have probably guessed, it is a synchronization bug in jython and
we will ofcourse add a fix to jython. Meanwhile you can change the
definition of your own PyFactory.initialize() to:

  public static synchronized void initialize() 
         throws ClassNotFoundException{
    pyInterp=new PythonInterpreter();
  }

as a workaround.

regards,
finn