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

java reflection invoke
brasskazoo picture brasskazoo · Oct 2, 2008 · Viewed 913.8k times · Source

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 String return value. It's a getter for a Java bean.

Answer

Henrik Paul picture Henrik Paul · Oct 2, 2008

Coding from the hip, it would be something like:

java.lang.reflect.Method method;
try {
  method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..);
} catch (SecurityException e) { ... }
  catch (NoSuchMethodException e) { ... }

The parameters identify the very specific method you need (if there are several overloaded available, if the method has no arguments, only give methodName).

Then you invoke that method by calling

try {
  method.invoke(obj, arg1, arg2,...);
} catch (IllegalArgumentException e) { ... }
  catch (IllegalAccessException e) { ... }
  catch (InvocationTargetException e) { ... }

Again, leave out the arguments in .invoke, if you don't have any. But yeah. Read about Java Reflection

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