Name: joT67522 Date: 10/01/97


/*
 * filename: test.java
 *
 * Cut out this code, compile and run it.
 *
 * OUTPUT description: The constructor gets called repeatedly.
 *
 * The reason for this lies in ResourceBundle.getBundle().
 * In ResourceBundle class, getBundle() uses findBundle()
 * first to look for a class with the given argument string
 * and it tries to instanstiate it. It does not check whether
 * it is a subclass of ResourceBundle before instantiating it.
 * Since the constructor for class test is public, there is
 * no problem with trying to instantiate it, and it will,
 * however ResourceBundle.getBundle() will be called
 * repeatedly.
 */

import java.util.ResourceBundle;

public class test
{
    String message = null;
    ResourceBundle rb;
    
    // remove the public access modifier for the constructor
    // and this code will work fine.
    public test()
    {
        System.out.println( "constructor called" );

        try
        {
            rb = ResourceBundle.getBundle( "test" );
            System.out.println( "read properties file" );
        }
        catch( Exception e )
        {
            System.err.println( "test.properties not found" );
            e.printStackTrace();
            System.exit( 1 );
        }

        try
        {
            message = rb.getString( "message" );
            System.out.println( message );
        }
        catch( Exception e )
        {
            e.printStackTrace();
        }
    }

    public static void main( String args[] )
    {
        test t = new test();
    }
}

//------------------------------------------
// Cut below the next line and remove the comments and save as test.properties
//------------------------------------------
message=Hello!
======================================================================


The bug actually covers two problems, only one of which is corrected by this fix:

Problem 1: ResourceBundle.getBundle does not find a .properties file. This occurs if you try to load a .properties file that has the same name as a class (and the class file does not descend from ResourceBundle). Ex. you have a class named MyClass (which does not descend from ResourceBundle) and a properties file named MyClass.properties. Resource bundle will try to return an object of type MyClass, fail when casting it to a ResourceBundle, and throw a ClassCastException. The .properties file is never looked for.

Problem 2: ResourceBundle.getBundle can cause an infinite recursion. This occurs when you meet the conditions of problem 1 AND you try to load the properties file from the class constructor or initialization code. ex. MyClass tries to load MyClass.properties from its constructor.

Problem 1 is corrected by this fix. Problem 2 is not.

johnfz@eng 1999-03-16