Commons Digester example source code file (AnnotationUtils.java)

This example Commons Digester source code file (AnnotationUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

annotation, annotation, annotationutils, annotationutils, object, object, pattern, pattern, string, string, throwable, value

The Commons Digester AnnotationUtils.java source code

/* $Id: AnnotationUtils.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * 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.
 */
package org.apache.commons.digester.annotations.utils;

import java.lang.annotation.Annotation;

import org.apache.commons.beanutils.MethodUtils;

/**
 * Simple utility class to introspect annotations.
 *
 * @since 2.1
 */
public class AnnotationUtils {

    /**
     * The {@code value} string constant.
     */
    private static final String VALUE = "value";

    /**
     * The {@code pattern} string constant.
     */
    private static final String PATTERN = "pattern";

    /**
     * This class can't be instantiated.
     */
    private AnnotationUtils() {
        // this class can' be instantiated
    }

    /**
     * Extract the {@code value()} from annotation.
     *
     * @param annotation the annotation has to be introspected.
     * @return the annotation {@code value()}.
     */
    public static Object getAnnotationValue(Annotation annotation) {
        return invokeAnnotationMethod(annotation, VALUE);
    }

    /**
     * Extract the {@code pattern()} from annotation.
     *
     * @param annotation the annotation has to be introspected.
     * @return the annotation {@code pattern()}.
     */
    public static String getAnnotationPattern(Annotation annotation) {
        Object ret = invokeAnnotationMethod(annotation, PATTERN);
        if (ret != null) {
            return (String) ret;
        }
        return null;
    }

    /**
     * Extract the Annotations array {@code value()} from annotation if present,
     * nul otherwise.
     *
     * @param annotation the annotation has to be introspected.
     * @return the annotation {@code value()} as Annotations array.
     */
    public static Annotation[] getAnnotationsArrayValue(Annotation annotation) {
        Object value = getAnnotationValue(annotation);
        if (value != null
                && value.getClass().isArray()
                && Annotation.class.isAssignableFrom(value.getClass().getComponentType())) {
            return (Annotation[]) value;
        }
        return null;
    }

    /**
     * Invokes an annotation method.
     *
     * @param annotationn the annotation has to be introspected.
     * @param method the method name to execute.
     * @return the annotation method value, null if any error occurs.
     */
    private static Object invokeAnnotationMethod(Annotation annotation, String method) {
        try {
            return MethodUtils.invokeExactMethod(annotation, method, null);
        } catch (Throwable t) {
            return null;
        }
    }

}