spring AOP 概述（三） Advisor

Advisor通知器

　　完成对目标方法的切面增强设计（Advice）和关注点的设计（Pointcut）以后，需要一个对象把它们结合起来，完成这个作用的就是Advisor（通知器）。通过Advisor，可以

定义应该使用哪个通知并在哪个关注点使用它，也就是说通过Advisor，把Advice和Pointcut结合起来。

　　我们以一个Advisor的实现（DefaultPointcutAdvisor）为例，来了解Advisor的工作原理，在DefaultPointcutAdvisor中，有两个属性，分别是advice和pointcut

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * 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
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 * 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.
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package org.springframework.aop.support;

import java.io.Serializable;

import org.aopalliance.aop.Advice;

import org.springframework.aop.Pointcut;

/**
 * Convenient Pointcut-driven Advisor implementation.
 *
 * <p>This is the most commonly used Advisor implementation. It can be used
 * with any pointcut and advice type, except for introductions. There is
 * normally no need to subclass this class, or to implement custom Advisors.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setPointcut
 * @see #setAdvice
 */
@SuppressWarnings("serial")
public class DefaultPointcutAdvisor extends AbstractGenericPointcutAdvisor implements Serializable {

    private Pointcut pointcut = Pointcut.TRUE;


    /**
     * Create an empty DefaultPointcutAdvisor.
     * <p>Advice must be set before use using setter methods.
     * Pointcut will normally be set also, but defaults to {@code Pointcut.TRUE}.
     */
    public DefaultPointcutAdvisor() {
    }

    /**
     * Create a DefaultPointcutAdvisor that matches all methods.
     * <p>{@code Pointcut.TRUE} will be used as Pointcut.
     * @param advice the Advice to use
     */
    public DefaultPointcutAdvisor(Advice advice) {
        this(Pointcut.TRUE, advice);
    }

    /**
     * Create a DefaultPointcutAdvisor, specifying Pointcut and Advice.
     * @param pointcut the Pointcut targeting the Advice
     * @param advice the Advice to run when Pointcut matches
     */
    public DefaultPointcutAdvisor(Pointcut pointcut, Advice advice) {
        this.pointcut = pointcut;
        setAdvice(advice);
    }


    /**
     * Specify the pointcut targeting the advice.
     * <p>Default is {@code Pointcut.TRUE}.
     * @see #setAdvice
     */
    public void setPointcut(Pointcut pointcut) {
        this.pointcut = (pointcut != null ? pointcut : Pointcut.TRUE);
    }

    public Pointcut getPointcut() {
        return this.pointcut;
    }


    @Override
    public String toString() {
        return getClass().getName() + ": pointcut [" + getPointcut() + "]; advice [" + getAdvice() + "]";
    }

}