Call to get an annotation that is expected on the given class, throwing a runtime exception if not found. - Java java.lang.annotation

Java examples for java.lang.annotation:Class Annotation

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Description

Call to get an annotation that is expected on the given class, throwing a runtime exception if not found.

Demo Code

/**/*  w  w  w . j  a v  a  2s  . co  m*/
 * Copyright (C) 2011 Tom Spencer <thegaffer@tpspencer.com>
 *
 * This file is part of TAL.
 *
 * TAL is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * TAL is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TAL. If not, see <http://www.gnu.org/licenses/>.
 *
 * Note on dates: Year above is the year this code was built. This
 * project first created in 2008. Code was created between these two
 * years inclusive.
 */
//package com.java2s;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

public class Main {
    public static void main(String[] argv) throws Exception {
        Class annotationType = String.class;
        Class cls = String.class;
        System.out.println(getExpectedAnnotation(annotationType, cls));
    }

    /**
     * Call to get an annotation that is expected on the given
     * class, throwing a runtime exception if not found.
     * 
     * @param annotationType The expected annotation
     * @param cls The Java class to check
     * @return The annotation
     * @throws IllegalArgumentException If annotation not found
     */
    public static <T extends Annotation> T getExpectedAnnotation(
            Class<T> annotationType, Class<?> cls) {
        T ret = cls.getAnnotation(annotationType);
        if (ret == null)
            throw new IllegalArgumentException("Expected annotation ["
                    + annotationType + "] not found on class: " + cls);
        return ret;
    }

    /**
     * Call to get an annotation that is expected on the given
     * method, throwing a runtime exception if not found.
     * 
     * @param annotationType The expected annotation
     * @param method The method to check
     * @return The annotation
     * @throws IllegalArgumentException If annotation not found
     */
    public static <T extends Annotation> T getExpectedAnnotation(
            Class<T> annotationType, Method method) {
        T ret = method.getAnnotation(annotationType);
        if (ret == null)
            throw new IllegalArgumentException("Expected annotation ["
                    + annotationType + "] not found on method: " + method);
        return ret;
    }
}

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