[JBoss-dev] Verify primary key implements equals and hashCode

[Dain Sundstrom]

After some email with Bill, it looks like we can use 
Class.getDeclaredMethods to find which method the class implements (you 
learn something new every day).  It specifically excludes inherited 
methods, so we can use it to verify if a primary key has actually 
implemented hashCode and equals.

Since equals equals is not really inheritable (see Effective Java), I 
think we should throw a verifier error if a pk does not directly 
implement it.  HashCode on the other hand can be inherited (and still 
be valid), so I think we should only print a warning if they don't 
directly.  We could check the parents until we get to Object to see if 
they left the default implementation.

Who maintains the verifier?

-dain

Here is the code I wrote in to test this:

   public static boolean definesEquals(Class clazz)
   {
      Method[] method = clazz.getDeclaredMethods();
      for(int i=0; i<method.length; i++)
      {
         if(method[i].getName().equals("equals") &&
               method[i].getParameterTypes().length == 1 &&
               method[i].getParameterTypes()[0] == Object.class &&
               method[i].getReturnType() == Boolean.TYPE)
         {
            return true;
         }
      }
      return false;
   }
   public static boolean definesHashCode(Class clazz)
   {
      Method[] method = clazz.getDeclaredMethods();
      for(int i=0; i<method.length; i++)
      {
         if(method[i].getName().equals("hashCode") &&
               method[i].getParameterTypes().length == 0 &&
               method[i].getReturnType() == Integer.TYPE)
         {
            return true;
         }
      }
      return false;
   }


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