10 Spring AOP

2019-03-09 本文已影响0人陶然然_niit

AOP（Aspect Oriented Programming，面向切面编程），通过提供另一种思考程序的方式来补充OOP（Object Oriented Programming，面向对象编程）。AOP是横向抽取，OOP是纵向抽象。
切面可以用于事务管理、日志等方面的模块化

AOP核心概念

Aspect（切面）
Join Point（连接点）
Advice（通知/增强）
Pointcut（切点）
Introduction（引入）
Target Object（目标对象）
AOP Proxy（AOP代理）
Weaving（织入）

其中，Advice的主要类型有:

Before Advice（前置通知）
After Returning Advice(返回后通知）
After Throwing Advice（抛出异常后通知）
After （finally）Advice（最后通知）
Around Advice（环绕通知）

切入点和连接点的匹配，是AOP的关键

Spring AOP

Spring AOP用纯Java实现，目前仅支持方法调用作为连接点。
Spring AOP通常和Spring IoC容器一起使用

Hello的前置增强练习

pom.xml中添加AOP相关依赖

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.spring</groupId>
    <artifactId>aop</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>aop</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <spring.version>5.1.5.RELEASE</spring.version>
        <aspectj.version>1.9.2</aspectj.version>
        <junit.version>4.12</junit.version>
        <log4j.version>1.2.17</log4j.version>
        <slf4j.version>1.7.12</slf4j.version>
    </properties>

    <dependencies>
        <!--spring-context依赖-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!--spring-aop依赖-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!--aspectj依赖-->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${aspectj.version}</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>${aspectj.version}</version>
        </dependency>
        <!--spring-test依赖-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!--junit依赖-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <!-- log4j日志依赖 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>${log4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
    </dependencies>

    <build>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
                <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                <plugin>
                    <artifactId>maven-site-plugin</artifactId>
                    <version>3.7.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-project-info-reports-plugin</artifactId>
                    <version>3.0.0</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

Hello接口和实现类

package com.spring.aop;

public interface Hello {
    String sayHello();
}

package com.spring.aop;

public class HelloImpl implements Hello {
    @Override
    public String sayHello() {
        return "Spring AOP";
    }
}

MyBefore类

package com.spring.aop;

/**
 * 用戶自定义前置增强类
 */
public class MyBefore {
    public void beforeMethod() {
        System.out.println("This is a before method...");
    }
 }

配置文件

    <bean id="hello" class="com.spring.aop.HelloImpl"/>
    <bean id="myBefore" class="com.spring.aop.MyBefore"/>
    <aop:config>
        <aop:aspect id="before" ref="myBefore">
            <aop:pointcut id="myPointcut" expression="execution(* com.spring.aop.*.*(..))"/>
            <aop:before method="beforeMethod" pointcut-ref="myPointcut"/>
        </aop:aspect>
    </aop:config>

应用主类

package com.spring.aop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class HelloApp {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        Hello hello = (Hello) ac.getBean("hello");
        System.out.println(hello.sayHello());
    }
}

运行结果

运行结果

可以看到：Mybefore的方法被织入到了Hello的调用方法前面，前置增强生效

实战：使用@AspectJ注解的例子

“武松打虎”——武松（Fighter）在山里等着老虎（Tiger）出现，只要发现老虎出来，就打老虎。

定义业务模型
Tiger类

package com.spring.aspectj;

public class Tiger {
    public void walk() {
        System.out.println("Tiger is walking...");
    }
}

定义切面和配置
前置通知和后置通知
Fighter类

package com.spring.aspectj;

import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class Fighter {
    @Pointcut("execution(* com.spring.aspectj.Tiger.walk())")
    public void foundTiger() {

    }

    @Before(value = "foundTiger()")
    public void foundBefore() {
        System.out.println("Fighter wait for tiger...");
    }

    @AfterReturning("foundTiger()")
    public void foundAfter() {
        System.out.println("Fighter fight with tiger...");
    }
}

配置文件

    <!--启动AspectJ支持-->
    <aop:aspectj-autoproxy/>
    <!--配置bean-->
    <bean id="tiger" class="com.spring.aspectj.Tiger"/>
    <bean id="fighter" class="com.spring.aspectj.Fighter"/>

主程序

package com.spring.aspectj;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class FighterApp {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Tiger tiger = context.getBean(Tiger.class);
        tiger.walk();
    }
}

运行结果

运行结果

10 Spring AOP

AOP核心概念

Spring AOP

Hello的前置增强练习

实战：使用@AspectJ注解的例子

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