code: public Class<?> getType(String key) {
        if (beanDescriptor.hasReadMethod(key)) {
           return beanDescriptor.getReadMethod(key).getReturnType();
        } else if (beanDescriptor.hasWriteMethod(key)) {
           Class<?>[] paramTypes = beanDescriptor.getWriteMethod(key).getParameterTypes();
           if (paramTypes.length > 0) {
              return paramTypes[0];
           }
        }
        return null;
     }
docs: Gets the type of the parameter on the setter method.
  
  @param key The setter method
  @return A <code>Class</code> representing the parameter type of the setter method