find Unique Annotated Method - Java java.lang.annotation

Java examples for java.lang.annotation:Method Annotation

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Description

find Unique Annotated Method

Demo Code

/*/*from  w  ww  . j  a  v a2  s  .  c  om*/
 * Copyright 2008 Whohoo Licensed under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable
 * law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 */
//package com.java2s;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

public class Main {
    public static void main(String[] argv) throws Exception {
        Object instance = "java2s.com";
        Class annotationClass = String.class;
        System.out.println(findUniqueAnnotedMethod(instance,
                annotationClass));
    }

    private static Method findUniqueAnnotedMethod(Object instance,
            Class<? extends Annotation> annotationClass) {
        Method methods[] = instance.getClass().getDeclaredMethods();
        Method postConstruct = null;
        for (int i = 0; i < methods.length; i++) {
            if (!methods[i].isAnnotationPresent(annotationClass)) {
                continue;
            }
            if (postConstruct != null
                    || methods[i].getParameterTypes().length != 0
                    || Modifier.isStatic(methods[i].getModifiers())
                    || methods[i].getExceptionTypes().length > 0
                    || !methods[i].getReturnType().getName().equals("void"))
                throw new IllegalArgumentException(
                        "Invalid method annotation");
            postConstruct = methods[i];
        }

        return postConstruct;
    }
}

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