Spring底层原理学习笔记--第九讲--(aop之ajc增强)

AOP实现之ajc编译器

AOP的另一种实现及原理

A10Application.java

package com.lucifer.itheima.a10;import com.lucifer.itheima.a10.service.MyService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;@SpringBootApplication
@Slf4j
public class A10Application {public static void main(String[] args) {ConfigurableApplicationContext context = SpringApplication.run(A10Application.class,args);MyService service = context.getBean(MyService.class);// 不是代理，说明aop的实现不只代理，这种没有用代理来实现，用的是aspect的编译器来进行增强，这个编译器的原理，就是把我们MyService的类改写了，改写后的class加入了前置增强，最终编译的class// 类在target->classes->包->MyService.class 把这个文件找到，然后拖到idea中来，idea就可以帮我们反编译，编译好的结果中，在我们的foo()方法中多了MyAspect// .aspectOf().before()方法的调用，所以是改写了class来实现增强，目标的类文件都被改写了，那还需要用代理吗，那就不需要了，既然class容器都被改写了，那么跟spring// 容器有关系吗，没有关系，我们的MyAspect切面类没有加@Component注解，说明他并不是由spring来管理的，它是由aspect的编译器来读到切面然后做的增强，并不是spring做的增强，log.info("service class：{}",service.getClass());service.foo();context.close();}
}

MyAspect.java

package com.lucifer.itheima.a10.aop;import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;@Aspect    //注意此切面未被spring管理
@Slf4j
public class MyAspect {@Before("execution(* com.lucifer.itheima.a10.service.MyService.foo())")public void before(){log.info("before()");}
}

MyService.java

package com.lucifer.itheima.a10.service;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;@Service
@Slf4j
public class MyService {public void foo(){log.info("foot()");}
}

pom.xml中添加插件

			<plugin><groupId>org.codehaus.mojo</groupId><artifactId>aspectj-maven-plugin</artifactId><version>1.14.0</version><configuration><comlianceLevel>1.8</comlianceLevel><source>8</source><target>8</target><showWeaveInfo>true</showWeaveInfo><verbose>true</verbose><Xlint>ignore</Xlint><encoding>UTF-8</encoding></configuration><executions><execution><goals><!-- use this goal to weave all your main classes--><goal>compile</goal><!-- use this goal to weave all your test classes--><goal>test-compile</goal></goals></execution></executions></plugin>

class文件中，显示的是：

MyService.class

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package com.lucifer.itheima.a10.service;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;@Service
public class MyService {private static final Logger log = LoggerFactory.getLogger(MyService.class);public MyService() {}public void foo() {MyAspect.aspectOf().before();log.info("foot()");}
}