AOP 面向切面程式設計

一、相關概念

Aspect:切面

PointCut:切點

Advisor:通知

共有五種通知：

Before:前置通知   

After:後置通知

Around:環繞通知（功能最強大）

AfterReturing:返回通知  （沒有異常的時候回執行）

AfterThrowing:異常通知 （有異常的時候回執行）

二、應用

<?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.example.beanValidation</groupId>
   <artifactId>demo</artifactId>
 
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>demo</name>
   <description>Demo project for Spring Boot</description>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
 
      <version>1.5.7.RELEASE</version>
      <relativePath/> <!-- lookup parent from repository -->
</parent>
   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-aop</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>
   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
</project>

建立一個切面WebLogAspect

package com.example.beanvalidation.aop;
import com.example.beanvalidation.exception.WrapException;
import com.fasterxml.jackson.databind.ObjectMapper;
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.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import java.util.Arrays;
/**
 * Created by sai.luo on 2017-9-19.
 */
@Component
@Aspect
public class WebLogAspect {

    private static final Logger log = LoggerFactory.getLogger(WebLogAspect.class);
    private static  final ObjectMapper objectMapper = new ObjectMapper();
/**
     * 定義切點
     */
@Pointcut("execution(* com.example.beanvalidation.controller..*.*(..))")
    public void webLog(){}
    /**
     * 定義前置通知
     */
@Before("webLog()")
    public void before(JoinPoint joinPoint){
        log.info("前置通知執行");
HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
//記錄日誌
String className = joinPoint.getTarget().getClass().getName();
String methodName = joinPoint.getSignature().getName();
log.info("請求方法："+className+"."+methodName);
log.info("請求引數："+ Arrays.asList(joinPoint.getArgs()[0]));
log.info("IP:"+request.getRemoteAddr());
}
    /**
     * 返回通知 不管是拋異常還是正常都是會執行
     */
@After("webLog()")
    public void after(){
        log.info("後置通知執行");
}
    /**
     * 定義環繞通知 方法簽名有返回型別
     */
@Around("webLog()")
    public Object  around(ProceedingJoinPoint proceedingJoinPoint)throws Throwable{
        log.info("環繞通知開始");
// 實際開發中需要定義一個返回類，包裝返回結果。
/**
         * public class ResponseResult{
         *   int code ;
         *   String message ;
         *   T result ;
         *
         *   // get set methods
         *   // constructor
         *   }
         */
try {
            Object proceed = proceedingJoinPoint.proceed();
log.info("返回正常結果："+objectMapper.writeValueAsString(proceed));
            return proceed;
}catch (WrapException ex){
           log.error("出現異常："+ex.getMessage());
}

        log.info("環繞通知結束");
        return null;
}
    /**
     * 異常通知 不建議使用異常通知，因為會使用系統輸出列印日誌，消耗系統資源，建議在環繞通知中 捕獲不同異常，進行處理
     */
@AfterThrowing(pointcut = "webLog()",throwing = "ex")
    public void afterThrowing(Throwable ex){
        log.info("異常通知");
log.error("error: "+ex.getMessage());
}

    /**
     * 正常返回通知
     */
@AfterReturning(pointcut = "webLog()",returning = "result")
    public void afterReturning(Object result)throws Exception{
        log.info("正常返回通知");
log.info(objectMapper.writeValueAsString(result));
}
}

如果切面類WenLogAspect不在main啟動類所在的包或者子包中，則需要手動注入到spring 容器中，才能生效