springboot aop使用介绍

Posted 2021-01-12 撸码识途

第一步：添加依赖

        <dependency>  
            <groupId>org.springframework.boot</groupId>  
            <artifactId>spring-boot-starter-aop</artifactId>  
        </dependency>  

第二步：定义一个切面类

package com.example.demo.aop;


import java.lang.reflect.Method;
import java.util.Arrays;

import javax.servlet.http.HttpServletRequest;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import static com.sun.xml.internal.ws.dump.LoggingDumpTube.Position.Before;

@Component
@Aspect // 将一个java类定义为切面类
@Order(-1)//如果有多个aop,这里可以定义优先级,越小级别越高
public class LogDemo {
    private static final Logger LOG = LoggerFactory.getLogger(LogDemo.class);

    @Pointcut("execution(* com.example.demo.test.TestController.test(..))")//两个..代表所有子目录，最后括号里的两个..代表所有参数
    public void logPointCut() {
    }

    @Before("logPointCut()")
    public void doBefore(JoinPoint joinPoint) throws Throwable {
        // 接收到请求，记录请求内容
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
        System.out.println("before");

    }

    @After(value = "logPointCut()")
    public void after(JoinPoint joinPoint) {
        System.out.println("after");
    }


    @AfterReturning(returning = "ret", pointcut = "logPointCut()")// returning的值和doAfterReturning的参数名一致
    public void doAfterReturning(Object ret) throws Throwable {
        System.out.println("AfterReturning");
    }

    @Around("logPointCut()")
    public void doAround(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("around1");
        Object ob = pjp.proceed();//环绕通知的进程方法不能省略，否则可能导致无法执行
        System.out.println("around2");
    }
}

注意：

如果同一个 切面类，定义了定义了两个 @Before，那么这两个 @Before的执行顺序是无法确定的

对于@Around，不管它有没有返回值，但是必须要方法内部，调用一下 pjp.proceed();否则，Controller 中的接口将没有机会被执行，从而也导致了 @Before不会被触发

 

测试的controller如下：

package com.example.demo.test;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;


@Controller
public class TestController {

    @RequestMapping(value = "test",method = RequestMethod.GET)
    @ResponseBody
    public String test(String name){
        System.out.println("============method");
        return name;
    }
}

 

配置完成，看看效果，输出如下：

around1
before
============method
around2
after
AfterReturning

可以看到，切面方法的执行如下：

around-->before-->method-->around-->after-->AfterReturning

如果配置了@AfterThrowing,当有异常时，执行如下：

around-->before-->method-->around-->after-->AfterThrowing