Finds all classes within a package which are annotated with certain annotation. - Java java.lang.annotation

Java examples for java.lang.annotation:Class Annotation

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Description

Finds all classes within a package which are annotated with certain annotation.

Demo Code

/*//w  w  w. j a  v  a  2  s  .  co m
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.io.File;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;

public class Main{

    /**
     * Finds all classes within a package which are annotated with certain
     * annotation.
     *
     * @param annotation  Annotation which we are looking for
     * @param <T>         Annotation class
     * @param packageName Package in which to search
     * @return The list of annotated classes
     */
    public static <T extends Annotation> List<Class<?>> getAnnotatedClasses(
            Class<T> annotation, String packageName) {
        ArrayList<Class<?>> ret = new ArrayList<Class<?>>();
        for (Iterator<Class<?>> it = getClassesIterator(packageName); it
                .hasNext();) {
            Class<?> clazz = it.next();
            if (clazz.getAnnotation(annotation) != null) {
                ret.add(clazz);
            }
        }
        return ret;
    }
    /**
     * @param packageName Package through which to iterate
     * @return Iterator through the classes of this jar file (if executed from
     *         jar) or through the classes of org package (if .class file is
     *         executed)
     */
    public static Iterator<Class<?>> getClassesIterator(String packageName) {
        if (isExecutedFromJar()) {
            try {
                return new JarClassesIterator(packageName);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        } else {
            return new GeneralClassesIterator(packageName);
        }
    }
    /**
     * @return Whether or not the code is executed from jar file
     */
    private static boolean isExecutedFromJar() {
        return AnnotationUtils.class.getResource("AnnotationUtils.class")
                .getProtocol().equals("jar");
    }
}

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