Name: nt126004 Date: 12/06/2001


java version "1.4.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta3-b84)
Java HotSpot(TM) Client VM (build 1.4.0-beta3-b84, mixed mode)

Introspection behaviour does not appear consistent on AIX and Windows. The AIX
VM seems to be more strict than the Windows version in its interpretation of
the bean specs.

In the TestBean.java class (below), according to the JavaBeans specs, there is a single
unambiguous property "p2" and an ambiguous property "p1". "p1" is ambiguous
because introspection cannot absolutely resolve the type of the property.

The sample below has 3 related methods:
 
    public int getP1();
    public void setP1(String s);
    public void setP1(int i);
 
The AIX VM correctly(I think) ignores the ambiguous property and hence its
corresponding "getter". The Windows VM returns a property P1 based on the signatures of the
first and third methods. Since the spec is not explicit on the subject
of a tie-breaker in such a situation and since without such a
specification there is no way the VM can intelligently recognize the
intentions of the coder, this is clearly not the right thing to do.
 
I feel that the Windows VM should be strict in this case, as the AIX
version is, and ignore the ambiguous property. Alternatively, the
specification could be made more explicit to cover this grey area.

Although I agree that the Windows VM works according to specs, I think
the specification itself is inadequate in this case and the Windows VM
handles the underspecification inappropriately. An underspecified area
in a standards document may allow multiple, correct interpretations.
However, where adhering to the wording of the spec clearly leads to the
acceptance of a fallacious situation, such adherance cannot be a good
thing.

Suppose you have the following class definition:

====BEGIN TestBean.java=================
public class TestBean
{
   public int getP1()
   {
      return 0;
   }

   public void setP1(String s)
   {
      return;
   }

   public void setP1(int i)
   {
      return;
   }

   public int getP2()
   {
      return 0;
   }

   public void setP2(int i)
   {
      return;
   }
}
====END TestBean.java===========================
====BEGIN CLASS TestPropertyGetter.java==============
/**
 * This class takes a class name parameter and a
 * property name parameter and prints out the results of introspection
 */
public class TestPropertyGetter
{
   /**
    * @param args
    */
   public static void main(String[] args)
   {
      try
      {
         String targetClassName = args[0];
         String targetPropertyName = args[1];
         Class class1 = Class.forName(targetClassName);
         String s = targetPropertyName;

         Method method = null;
         Class class2 = null;

         try
         {
            BeanInfo beaninfo = Introspector.getBeanInfo(class1);
            if(beaninfo != null)
            {
                PropertyDescriptor apropertydescriptor[] =
beaninfo.getPropertyDescriptors();
                for(int i = 0; i < apropertydescriptor.length; i++)
                {
                    if(!apropertydescriptor[i].getName().equals(s))
                    {
                        continue;
                    }

                    System.out.println("Located property descriptor " +
apropertydescriptor[i].getName());
                    method = apropertydescriptor[i].getReadMethod();
                    class2 = apropertydescriptor[i].getPropertyType();
                    break;
                }

            }
            else
            {
                System.out.println("jsp.error.beans.nobeaninfo");
            }
        }
        catch(Exception exception)
        {
            System.out.println(exception.getClass().getName() + ">" +
exception.getMessage());
        }
        if(method == null)
        {
            if(class2 == null)
            {
                System.out.println("jsp.error.beans.noproperty");
            }
            else
            {
                System.out.println("jsp.error.beans.nomethod");
            }
        } else
        {
            System.out.println("Success finding method " + method.getName());
        }

      }
      catch (Exception e)
      {
         e.printStackTrace();
      }

   }
}
========END CLASS TestPropertyGetter.java==============
(Review ID: 136363)
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