CODEWITHSUNDEEP
javareflection
Andriy Drozdyuk
Andriy Drozdyuk

Reputation: 61121

How to get string name of a method in java?

How can I find out through reflection what is the string name of the method?

For example given:

class Car{
   public void getFoo(){
   }
}

I want to get the string "getFoo", something like the following:

 Car.getFoo.toString() == "getFoo" // TRUE

Upvotes: 37

Views: 85853

Answers (7)

Jan Gassen
Jan Gassen

Reputation: 3534

With Java 8, you can do this with a few lines of code (almost) without any additional libraries. The key is to convert your method into a serialisable lambda expression. Therefore, you can just define a simple interface like this:

@FunctionalInterface
public interface SerializableFunction<I, O> extends Function<I, O>, Serializable {
  // Combined interface for Function and Serializable
}

Now, we need to convert our lambda expression into a SerializedLambda object. Apparently, Oracle does not really want us to do that, so take this with a grain of salt... As the required method is private, we need to invoke it using reflections:

private static final <T> String nameOf(SerializableFunction<T, ?> lambda) {
  Method findMethod = ReflectionUtils.findMethod(lambda.getClass(), "writeReplace");
  findMethod.setAccessible(true);

  SerializedLambda invokeMethod = (SerializedLambda) ReflectionUtils.invokeMethod(findMethod, lambda);
  return invokeMethod.getImplMethodName();
}

I'm using Springs ReflectionUtils class here for simplicity, but you can of course replace this by manually looping through all superclasses and use getDeclaredMethod to find the writeReplace method.

And this is it already, now you can use it like this:

@Test
public void testNameOf() throws Throwable {
  assertEquals("getName", nameOf(MyClassTest::getName));
}

I haven't checked this with Java 9s module system, so as a little disclaimer it might be more tricky to do this with more recent Java versions...

Upvotes: 4

olivmir
olivmir

Reputation: 722

Look into this thread:

Getting the name of the currently executing method

It offers some more solutions - for example:

String name = new Object(){}.getClass().getEnclosingMethod().getName();

Upvotes: 10

Malcolm
Malcolm

Reputation: 41498

You can get the String like this:

Car.class.getDeclaredMethods()[0].getName();

This is for the case of a single method in your class. If you want to iterate through all the declared methods, you'll have to iterate through the array returned by Car.class.getDeclaredMethods():

for (Method method : Car.class.getDeclaredMethods()) {
    String name = method.getName();
}

You should use getDeclaredMethods() if you want to view all of them, getMethods() will return only public methods.

And finally, if you want to see the name of the method, which is executing at the moment, you should use this code:

Thread.currentThread().getStackTrace()[1].getMethodName();

This will get a stack trace for the current thread and return the name of the method on its top.

Upvotes: 41

Jesper
Jesper

Reputation: 207006

So, you want to get the name of the currently executing method? Here's a somewhat ugly way to do that:

Exception e = new Exception();
e.fillInStackTrace();
String methodName = e.getStackTrace()[0].getMethodName();

Upvotes: 15

zhy2002
zhy2002

Reputation: 389

try this,

 import java.lang.reflect.*;
    public class DumpMethods {
        public static void main(String args[]) {
            try {
                Class c = Class.forName(args[0]);
                Method m[] = c.getDeclaredMethods();
                for (int i = 0; i < m.length; i++)
                    System.out.println(m[i].toString());
            } catch (Throwable e) {
                System.err.println(e);
            }
        }
    }

Upvotes: 1

Bozho
Bozho

Reputation: 597412

Wait, since you already know the method name, can't you just type it as a string?

Instead of (pseudo) Class.methodName.toString(), just use "methodName".

Otherwise you can use Class#getDeclaredMethods() to get all the methods in a class

Upvotes: 0

Matt
Matt

Reputation: 44078

Since methods aren't objects themselves, they don't have direct properties (like you would expect with first-class functions in languages like JavaScript).

The closest you can do is call Car.class.getMethods()

Car.class is a Class object which you can use to invoke any of the reflection methods.

However, as far as I know, a method is not able to identify itself.

Upvotes: 24

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