How do I invoke a Java method when given the method name as a string?

Question

If I have two variables:

Object obj; String methodName = "getName";

Without knowing the class of obj, how can I call the method identified by methodName on it?

The method being called has no parameters, and a Stringreturn value. It's a getter for a Java bean.

Answer 1

From Java Reflection, you can use method invocation to call the method identified by methodName on it without knowing the class of the object:

java.lang.reflect.Method method;

try {

  method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..);

} catch (SecurityException e) { ... }

  catch (NoSuchMethodException e) { ... }

The parameters recognize the very specific method we need (if there are many overloaded available, if the method has no arguments, only give methodName).

 

To invoke that method, use:

try {

  method.invoke(obj, arg1, arg2,...);

} catch (IllegalArgumentException e) { ... }

  catch (IllegalAccessException e) { ... }

  catch (InvocationTargetException e) { ... }

In case if there aren't any arguments in .invoke,  then exclude it.