DefaultAnnotationResolver.java

/*
 *
 *  * Copyright (c) 2016. David Sowerby
 *  *
 *  * 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 uk.q3c.krail.core.shiro.aop;


import org.aopalliance.intercept.MethodInvocation;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

/**
 * Copied from the original Shiro implementation
 *
 * Default {@code AnnotationResolver} implementation that merely inspects the
 * {@link MethodInvocation MethodInvocation}'s {@link MethodInvocation#getMethod() target method},
 * and returns {@code targetMethod}.{@link Method#getAnnotation(Class) getAnnotation(class)}.
 * <p>
 * Unfortunately Java's default reflection API for Annotations is not very robust, and this logic
 * may not be enough - if the incoming method invocation represents a method from an interface,
 * this default logic would not discover the annotation if it existed on the method implementation
 * directly (as opposed to being defined directly in the interface definition).
 * <p>
 * More complex class hierarchy traversal logic is required to exhaust a method's target object's
 * classes, parent classes, interfaces and parent interfaces.  That logic will likely be added
 * to this implementation in due time, but for now, this implementation relies on the JDK's default
 * {@link Method#getAnnotation(Class) Method.getAnnotation(class)} logic.
 *
 * @since 1.1
 */
public class DefaultAnnotationResolver implements AnnotationResolver {

    /**
     * Returns {@code methodInvocation.}{@link org.apache.shiro.aop.MethodInvocation#getMethod() getMethod()}.{@link Method#getAnnotation(Class)
     * getAnnotation(clazz)}.
     *
     * @param mi
     *         the intercepted method to be invoked.
     * @param clazz
     *         the annotation class to use to find an annotation instance on the method.
     *
     * @return the discovered annotation or {@code null} if an annotation instance could not be
     * found.
     */
    @Override
    public <A extends Annotation> A getAnnotation(MethodInvocation mi, Class<A> clazz) {
        if (mi == null) {
            throw new IllegalArgumentException("method argument cannot be null");
        }
        Method m = mi.getMethod();
        if (m == null) {
            String msg = MethodInvocation.class.getName() + " parameter incorrectly constructed.  getMethod() returned null";
            throw new IllegalArgumentException(msg);

        }
        A annotation = m.getAnnotation(clazz);
        return annotation == null ? mi.getThis()
                                      .getClass()
                                      .getAnnotation(clazz) : annotation;
    }
}