Spring学习(十八)----- Spring AOP+AspectJ注解实例

谁借莪１个温暖的怀抱￠ 2022-03-14 08:33 174阅读 0赞

[Spring学习(十八)----- Spring AOP+AspectJ注解实例][Spring_----- Spring AOP_AspectJ]

我们将向你展示如何将AspectJ注解集成到Spring AOP框架。在这个Spring AOP+ AspectJ 示例中，让您轻松实现拦截方法。

常见AspectJ的注解：

1.  @Before – 方法执行前运行
2.  @After – 运行在方法返回结果后
3.  @AfterReturning – 运行在方法返回一个结果后，在拦截器返回结果。
4.  @AfterThrowing – 运行方法在抛出异常后，
5.  @Around – 围绕方法执行运行，结合以上这三个通知。

## 1. 目录结构 ##

看到这个例子的目录结构。  
![1-15122H0213Q04.png][]

## 2. Spring Beans ##

普通 bean 中有几个方法，后来通过 AspectJ 注解拦截。

package com.yiibai.customer.bo;
    
    public interface CustomerBo {
    
        void addCustomer();
        
        String addCustomerReturnValue();
        
        void addCustomerThrowException() throws Exception;
        
        void addCustomerAround(String name);
    }
    
    package com.yiibai.customer.bo.impl;
    
    import com.yiibai.customer.bo.CustomerBo;
    
    public class CustomerBoImpl implements CustomerBo {
    
        public void addCustomer(){
            System.out.println("addCustomer() is running ");
        }
        
        public String addCustomerReturnValue(){
            System.out.println("addCustomerReturnValue() is running ");
            return "abc";
        }
        
        public void addCustomerThrowException() throws Exception {
            System.out.println("addCustomerThrowException() is running ");
            throw new Exception("Generic Error");
        }
        
        public void addCustomerAround(String name){
            System.out.println("addCustomerAround() is running, args : " + name);
        }
    }

## 4. 启用AspectJ ##

在 Spring 配置文件，把“<aop:aspectj-autoproxy />”，并定义Aspect(拦截)和普通的bean。

*File : applicationContext.xml*

## 4. AspectJ @Before ##

在下面例子中，logBefore()方法将在 customerBo接口的 addCustomer()方法的执行之前被执行。

AspectJ的“切入点”是用来声明哪种方法将被拦截，应该参考[Spring AOP切入点指南][Spring AOP]，支持切入点表达式的完整列表。

*File : LoggingAspect.java*

package com.yiibai.aspect;
    
    import org.aspectj.lang.JoinYiibai;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.Before;
    
    @Aspect
    public class LoggingAspect {
    
        @Before("execution(* com.yiibai.customer.bo.CustomerBo.addCustomer(..))")
        public void logBefore(JoinYiibai joinYiibai) {
    
            System.out.println("logBefore() is running!");
            System.out.println("hijacked : " + joinYiibai.getSignature().getName());
            System.out.println("******");
        }
    
    }

运行

CustomerBo customer = (CustomerBo) appContext.getBean("customerBo");
    customer.addCustomer();

输出结果

logBefore() is running!
    hijacked : addCustomer
    ******
    addCustomer() is running

## 5. AspectJ @After ##

在下面例子中，logAfter()方法将在 customerBo 接口的 addCustomer()方法的执行之后执行。

*File : LoggingAspect.java*

package com.yiibai.aspect;
    
    import org.aspectj.lang.JoinYiibai;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.After;
    
    @Aspect
    public class LoggingAspect {
    
        @After("execution(* com.yiibai.customer.bo.CustomerBo.addCustomer(..))")
        public void logAfter(JoinYiibai joinYiibai) {
    
            System.out.println("logAfter() is running!");
            System.out.println("hijacked : " + joinYiibai.getSignature().getName());
            System.out.println("******");
    
        }
    
    }

运行它

CustomerBo customer = (CustomerBo) appContext.getBean("customerBo");
    customer.addCustomer();

输出结果

addCustomer() is running 
    logAfter() is running!
    hijacked : addCustomer
    ******

## 6. AspectJ @AfterReturning ##

在下面例子中，logAfterReturning()方法将在 customerBo 接口的addCustomerReturnValue()方法执行之后执行。此外，还可以截取返回的值使用“returning”属性。

要截取返回的值，对“returning”属性(结果)的值必须用相同的方法参数(结果)。

*File : LoggingAspect.java*

package com.yiibai.aspect;
    
    import org.aspectj.lang.JoinYiibai;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.AfterReturning;
    
    @Aspect
    public class LoggingAspect {
    
       @AfterReturning(
          pointcut = "execution(* com.yiibai.customer.bo.CustomerBo.addCustomerReturnValue(..))",
          returning= "result")
       public void logAfterReturning(JoinYiibai joinYiibai, Object result) {
    
        System.out.println("logAfterReturning() is running!");
        System.out.println("hijacked : " + joinYiibai.getSignature().getName());
        System.out.println("Method returned value is : " + result);
        System.out.println("******");
       }
    }

运行它

CustomerBo customer = (CustomerBo) appContext.getBean("customerBo");
        customer.addCustomerReturnValue();

输出结果

addCustomerReturnValue() is running 
    logAfterReturning() is running!
    hijacked : addCustomerReturnValue
    Method returned value is : abc
    ******

## 7. AspectJ @AfterReturning ##

在下面的例子中，如果 customerBo 接口的addCustomerThrowException()方法抛出异常logAfterThrowing()方法将被执行。

*File : LoggingAspect.java*

package com.yiibai.aspect;
    
    import org.aspectj.lang.JoinYiibai;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.AfterThrowing;
    
    @Aspect
    public class LoggingAspect {
    
       @AfterThrowing(
          pointcut = "execution(* com.yiibai.customer.bo.CustomerBo.addCustomerThrowException(..))",
          throwing= "error")
        public void logAfterThrowing(JoinYiibai joinYiibai, Throwable error) {
    
        System.out.println("logAfterThrowing() is running!");
        System.out.println("hijacked : " + joinYiibai.getSignature().getName());
        System.out.println("Exception : " + error);
        System.out.println("******");
    
        }
    }

运行它

CustomerBo customer = (CustomerBo) appContext.getBean("customerBo");
    customer.addCustomerThrowException();

输出结果

![复制代码][copycode.gif]

addCustomerThrowException() is running 
    logAfterThrowing() is running!
    hijacked : addCustomerThrowException
    Exception : java.lang.Exception: Generic Error
    ******
    Exception in thread "main" java.lang.Exception: Generic Error
        //...

![复制代码][copycode.gif]

## 8. AspectJ @Around ##

在下面例子中，logAround()方法将在customerBo接口的addCustomerAround()方法执行之前执行， 必须定义“joinYiibai.proceed();” 控制何时拦截器返回控制到原来的addCustomerAround()方法。

*File : LoggingAspect.java*

package com.yiibai.aspect;
    
    import org.aspectj.lang.ProceedingJoinYiibai;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.Around;
    
    @Aspect
    public class LoggingAspect {
    
       @Around("execution(* com.yiibai.customer.bo.CustomerBo.addCustomerAround(..))")
       public void logAround(ProceedingJoinYiibai joinYiibai) throws Throwable {
    
        System.out.println("logAround() is running!");
        System.out.println("hijacked method : " + joinYiibai.getSignature().getName());
        System.out.println("hijacked arguments : " + Arrays.toString(joinYiibai.getArgs()));
            
        System.out.println("Around before is running!");
        joinYiibai.proceed(); //continue on the intercepted method
        System.out.println("Around after is running!");
            
        System.out.println("******");
    
       }
        
    }

运行它

CustomerBo customer = (CustomerBo) appContext.getBean("customerBo");
    customer.addCustomerAround("yiibai");

输出结果

![复制代码][copycode.gif]

logAround() is running!
    hijacked method : addCustomerAround
    hijacked arguments : [yiibai]
    Around before is running!
    addCustomerAround() is running, args : yiibai
    Around after is running!
    ******

![复制代码][copycode.gif]

## 总结 ##

它总是建议采用最少 AspectJ 注解。这是关于Spring AspectJ 的一篇相当长的文章。进一步的解释和例子，请访问下面的参考链接。

[Spring_----- Spring AOP_AspectJ]: https://www.cnblogs.com/zy-jiayou/p/7747910.html
[1-15122H0213Q04.png]: /images/20220313/55a83964d2614abbb1f7c9c6f15bb133.png
[Spring AOP]: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/aop.html#aop-pointcuts
[copycode.gif]: /images/20220313/2a1769cdcbee4067a51de4d28800e62b.png