dynamic method call using reflection only works with certain methods?

[Soefara]

Dear all,

I'm really struggling to see what's wrong with the following
method which uses reflection to dynamically call a method
of an object.

It compiles fine, but when I pass it a String instance and
the methodName "toUpperCase" or "toLowerCase" it reports
no such method found. It does however work with "toString" !

The same thing happens with any other class objects I pass
it. About the only methodName that is understood is "toString".
Anything else will return the "no such method" error

Am I missing something obvious here?

-------------------------------------------------------------

// Call a method of an object with no arguments/parameters.
public static Object callMethod(Object obj, String methodName) {
Class c = Object.class;
Object result = null;
try {
Method m = c.getMethod(methodName, new Class[]{});
result = m.invoke(obj, new Object[]{} );
}
catch(java.lang.NoSuchMethodException e) {
System.out.println("Error - No such method: \n" + e.getMessage());
}
catch(java.lang.IllegalAccessException e) {
System.out.println("Error - Illegal access: \n" + e.getMessage());
}
catch (java.lang.reflect.InvocationTargetException e) {
System.out.println("Error - Reflection error : \n" + e.getMessage());
}
return result;
}

-------------------------------------------------------------


Thank you very much in advance,

Soefara

 

[Robert Olofsson]

Soefara ([email protected]) wrote:
: public static Object callMethod(Object obj, String methodName) {
: Class c = Object.class;
: Object result = null;
: try {
: Method m = c.getMethod(methodName, new Class[]{});

Hmm, c is the class Object, not the class of obj. That is the
misstake right?

Object does have a toString, but it does not have a toUpperCase.

/robo

 

[pete kirkham]

You also will need to specify the types and classes of the parameters if
you are trying to find a method which takes any.

Pete