Spring Boot1.5.4 AOP实例

原文：https://github.com/x113773/testall/issues/12

1. 还是首先添加依赖（使用当前springboot的默认版本）
```
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>

```
- 参考下面[官方文档](http://docs.spring.io/spring-boot/docs/1.5.4.RELEASE/reference/htmlsingle/)的部分配置说明，可见aop是默认开启的，自动添加了@EnableAspectJAutoProxy注解
```
# AOP
spring.aop.auto=true # Add @EnableAspectJAutoProxy.
spring.aop.proxy-target-class=false # Whether subclass-based (CGLIB) proxies are to be created (true) as opposed to standard Java interface-based proxies (false).
```

2. 编写一个切面类，[AspectAdviceConfig.java](https://github.com/x113773/testall/blob/master/src/main/java/com/ansel/testall/aop/AspectAdviceConfig.java)，里面定义了一个切点指示器和各种通知(Advice，也译作 增强)

```
package com.ansel.testall.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.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.DeclareParents;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
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;

@Aspect
@Component
public class AspectAdviceConfig {
private Logger logger = LoggerFactory.getLogger(this.getClass());

/**
* 定义切点指示器：com.ansel.testall.aop包下，带@RestController注解的类。
*/
@Pointcut("execution(* com.ansel.testall.aop..*(..)) and @annotation(org.springframework.web.bind.annotation.RestController)")
public void myPointcut() {
}

/**
* 前置通知，在目标方法完成之后调用通知，此时不会关 心方法的输出是什么
*/
@Before("myPointcut()")
public void beforeAdvice() {
System.out.println("Before--通知方法会在目标方法调用之前执行");
}

/**
* 后置通知，在目标方法完成之后调用通知，此时不会关 心方法的输出是什么
*/
@After("myPointcut()")
public void afterAdvice() {
System.out.println("After--通知方法会在目标方法返回或抛出异常后调用");
}

/**
* 返回通知，在目标方法成功执行之后调用，可以获得目标方法的返回值，但不能修改（修改也不影响方法的返回值）
*
* @param jp
* JoinPoint接口，可以获得连接点的一些信息
*
* @param retVal
* 目标方法返回值，和jp一样会由spring自动传入
*/
@AfterReturning(returning = "retVal", pointcut = "myPointcut()")
public void afterReturningAdvice(JoinPoint jp, Object retVal) {
retVal = retVal + " (@AfterReturning can read the return value, but it can't change the value!)";
System.out.println("AfterReturning--通知方法会在目标方法返回后调用; retVal = " + retVal);
System.out.println(jp.toLongString());
}

/**
* 异常通知，在目标方法抛出异常后调用通知
*/

@AfterThrowing("myPointcut()")
public void afterThrowingAdvice() {
System.out.println("AfterThrowing--通知方法会在目标方法抛出异常后调用");
}

/**
* 环绕通知，可以在目标方法调用前后，自定义执行内容。可以修改目标方法的返回值
*
* @param pjp
*/
@Around("myPointcut()")
public Object aroundAdvice(ProceedingJoinPoint pjp) {
Object retVal = null;
try {
System.out.println("Around--目标方法调用之前执行");

ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = attributes.getRequest();

MethodSignature signature = (MethodSignature) pjp.getSignature();
Method method = signature.getMethod(); // 获取被拦截的方法
String methodName = method.getName(); // 获取被拦截的方法名

logger.info("requset method name is: " + methodName);
logger.info("request URL is: " + request.getRequestURL().toString());
logger.info("request http method: " + request.getMethod());
logger.info("request arguments are: " + Arrays.toString(pjp.getArgs()));

retVal = pjp.proceed();
retVal = retVal + " (@Around can change the return value!)";

System.out.println("Around--目标方法返回后调用");
} catch (Throwable e) {
System.out.println("Around--目标方法抛出异常后调用");
}
return retVal;
}
}

```
3. 通过Advice可以某些方法增加一些功能，若要为某个对象增加新的方法，则要用到Introduction，编写另外一个切面AspectIntroductionConfig.java

```
package com.ansel.testall.aop;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class AspectIntroductionConfig {

/**
* DeclareParents注解所标注的静态属性指明了要引入的接口;
* value属性指定了哪种类型的bean要引入该接口;
* defaultImpl属性指定了为引入功能提供实现的类。
*/
@DeclareParents(value = "com.ansel.testall.aop.AopService+", defaultImpl = IntroductionServiceImpl.class)
public static IntroductionService introductionService;
}

```
4. 编写两个接口AopService、IntroductionService，和2个实现AopServiceImpl、IntroductionServiceImpl

```
package com.ansel.testall.aop;

public interface AopService {
String myOwnMethod();
}
/***********************************/
package com.ansel.testall.aop;

public interface IntroductionService {
String IntroductionMethod();
}
/***********************************/
package com.ansel.testall.aop;

import org.springframework.stereotype.Service;

@Service
public class AopServiceImpl implements AopService {

@Override
public String myOwnMethod() {
return "this method is from AopService";
}

}
/***********************************/
package com.ansel.testall.aop;

import org.springframework.stereotype.Service;

@Service
public class IntroductionServiceImpl implements IntroductionService {

@Override
public String IntroductionMethod() {
return "this method from Introduction.";
}

}
```

5. 编写一个切点实例[AopController.java](https://github.com/x113773/testall/blob/master/src/main/java/com/ansel/testall/aop/AopController.java) (其实就是个普通的controller)

```
package com.ansel.testall.aop;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AopController {

/**
* 只注入AopService
*/
@Autowired
AopService aopService;

/**
* 测试AOP通知(Advice，也译作 增强)
*
* @return
*/
@RequestMapping(value = "/aop", method = RequestMethod.GET)
public String testAop() {
return "this is a AOP Advice test.";
}

/**
* 测试AOP引入(Introduction)
*
* @return
*/
@RequestMapping(value = "/aop/introdution", method = RequestMethod.GET)
public String testAopIntroduction() {
System.out.println(aopService.myOwnMethod());
//接口类型转换
IntroductionService introductionService = (IntroductionService) aopService;
System.out.println(introductionService.IntroductionMethod());
return "this is a AOP Introduction test.";
}
}

```

4. 启动项目，触发 localhost:8080/aop 请求，控制台输出结果如下：

```
Around--目标方法调用之前执行
2017-07-03 17:33:15.494 INFO 8548 --- [nio-8443-exec-7] tConfig$$EnhancerBySpringCGLIB$$5f4562fb : requset method name is: testAOP
2017-07-03 17:33:15.495 INFO 8548 --- [nio-8443-exec-7] tConfig$$EnhancerBySpringCGLIB$$5f4562fb : request URL is: https://localhost:8443/aop
2017-07-03 17:33:15.495 INFO 8548 --- [nio-8443-exec-7] tConfig$$EnhancerBySpringCGLIB$$5f4562fb : request http method: GET
2017-07-03 17:33:15.495 INFO 8548 --- [nio-8443-exec-7] tConfig$$EnhancerBySpringCGLIB$$5f4562fb : request arguments are: []
Before--通知方法会在目标方法调用之前执行
Around--目标方法返回后调用
After--通知方法会在目标方法返回或抛出异常后调用
AfterReturning--通知方法会在目标方法返回后调用; retVal = this is a AOP test. (@Around can change the return value!) (@AfterReturning can read the return value, but it can't change the value!)
execution(public java.lang.String com.ansel.testall.aop.AOPController.testAOP())
```

页面返回结果如下：
`this is a AOP test. (@Around can change the return value!)`

触发 localhost:8080/aop/introdution 请求，控制台输出结果如下：


---
注：

`@Pointcut("execution(* com.ansel.testall.aop..*(..)) and @annotation(org.springframework.web.bind.annotation.RestController)")`

当我使用and操作符连接上面两个切点指示器，没有任何问题（把注解RestController换成RequestMapping也没问题）
然而，当我使用&&操作符连接上面两个切点指示器时，完全没有触发AspectJ，切面没有织入任何连接点（把注解RestController换成RequestMapping就没问题）

```
/**
* OK
*/
@Pointcut("execution(* com.ansel.testall.aop..*(..)) and @annotation(org.springframework.web.bind.annotation.RestController)")

/**
* not OK
*/
@Pointcut("execution(* com.ansel.testall.aop..*(..)) && @annotation(org.springframework.web.bind.annotation.RestController)")

/**
* OK
*/
@Pointcut("execution(* com.ansel.testall.aop..*(..)) and @annotation(org.springframework.web.bind.annotation.RequestMapping)")

/**
* OK
*/
@Pointcut("execution(* com.ansel.testall.aop..*(..)) && @annotation(org.springframework.web.bind.annotation.RequestMapping)")
```