利用AOP实现自定义注解

最近有个新需求，是对用户的某些操作进行监控，操作记录要写入数据库，首先想到了使用Filter过滤器和Spring的Interceptor(拦截器)，这两种都需要复杂的配置（能用代码解决的问题绝不上手），于是灵机一动想到了基于注解实现AOP,在要进行监控的Action加上该注解，完美，开始！

编写自定义注解

package com.asiainfo.annotation;

import java.lang.annotation.*;

/**
 * @description: 自动以注解
 * @author: Mr-box
 * @create: 2019-05-23 10:00
 **/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Documented

public @interface EagleEye {

    String desc() default "";

}
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• 定义注解的生命周期为运行时
• 定义注解的作用于为方法
• 标记注解可以被JavaDoc记录
• 定义注解为EagleEye（鹰眼）
• 定义desc，用来描述被修饰的方法

定义AOP切面

package com.asiainfo.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
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;

/**
 * @description: 定义AOP切面
 * @author: Mr-box
 * @create: 2019-05-23 10:00
 **/

@Aspect
@Component
public class LogAspect {

    // 定义切点
    @Pointcut("@annotation(com.asiainfo.annotation.EagleEye)")
    public void eagleEye() {

    }

    // 利用环绕增强来实现我们的功能
    @Around("eagleEye()")
    public Object surroundInform(ProceedingJoinPoint proceedingJoinPoint) {

        System.out.println("环绕通知开始...");
        
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();

        System.out.println("请求路径 : " + request.getRequestURL());
        System.out.println("请求方式 : " + request.getMethod());
        System.out.println("方法名 : " + proceedingJoinPoint.getSignature().getName());
        System.out.println("类路径 : " + proceedingJoinPoint.getSignature().getDeclaringTypeName());
        System.out.println("参数 : " + Arrays.toString(proceedingJoinPoint.getArgs()));
        
        try {
            // 真实业务代码，这里是伪代码
            Object o =  proceedingJoinPoint.proceed();
            System.out.println("方法环绕proceed，结果是 :" + o);
            return o;
        } catch (Throwable e) {
            e.printStackTrace();
            return null;
        }
    }
}
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注解的使用

• 在方法上加入@EagleEye(desc = "测试接口")注解即可实现

package com.asiainfo.action;

import com.asiainfo.annotation.EagleEye;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @description: 定义AOP切面
 * @author: Mr-box
 * @create: 2019-05-23 10:00
 **/
 
@RestController
public class TestAction {

    @EagleEye(desc = "测试接口")
    @RequestMapping(value = "/sayHello")
    public String test(String params)throws Exception{
        System.out.println("参数:" + params);
        return "hello "+ params;
    }
}
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启动测试

浏览器调用： http://127.0.0.1:8081/aop-demo/sayHello?params=lala
观察日志输出：

.   ____          _            __ _ _
 /// / ___'_ __ _ _(_)_ __  __ _ / / / /
( ( )/___ | '_ | '_| | '_ // _` | / / / /
 ///  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_/__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

2019-05-23 10:00  INFO 3183 --- [           main] com.asiainfo.SpringAopDemoApplication    : Starting SpringAopDemoApplication on zhangdsdeiMac.local with PID 3183 (/Users/zhangds/Development/code/spring-aop-demo/target/classes started by zhangds in /Users/zhangds/Development/code/spring-aop-demo)
2019-05-23 10:00  INFO 3183 --- [           main] com.asiainfo.SpringAopDemoApplication    : No active profile set, falling back to default profiles: default
2019-05-23 10:00  INFO 3183 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8081 (http)
2019-05-23 10:00  INFO 3183 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-05-23 10:00  INFO 3183 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.31]
2019-05-23 10:00  INFO 3183 --- [           main] o.a.c.c.C.[.[localhost].[/aop-demo]      : Initializing Spring embedded WebApplicationContext
2019-05-23 10:00  INFO 3183 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 627 ms
2019-05-23 10:00  INFO 3183 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-05-23 10:00  INFO 3183 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8081 (http) with context path '/aop-demo'
2019-05-23 10:00  INFO 3183 --- [           main] com.asiainfo.SpringAopDemoApplication    : Started SpringAopDemoApplication in 1.115 seconds (JVM running for 1.654)
2019-05-23 10:00  INFO 3183 --- [nio-8081-exec-1] o.a.c.c.C.[.[localhost].[/aop-demo]      : Initializing Spring DispatcherServlet 'dispatcherServlet'
2019-05-23 10:00  INFO 3183 --- [nio-8081-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2019-05-23 10:00  INFO 3183 --- [nio-8081-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 4 ms
请求路径 : http://127.0.0.1:8081/aop-demo/sayHello
请求方式 : GET
方法名 : test
类路径 : com.asiainfo.action.TestAction
参数 : [lala]
环绕通知开始...
参数:lala
方法环绕proceed，结果是 :hello lala
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总结

• 要比配置切点用execution表达式灵活性要高，execution表达式具有一定的局限性。
• 自定义注解灵活性比较高，但这只是自定义注解的小用法而已。