AspectJ是主流的AOP框架,Spring在其AOP中支持AspectJ註解編寫的POJO aspect。
首先我們需要在Bean配置文件中啓用,只要使用標籤<aop:aspectj-autoproxy>
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
">
<!-- 添加註解功能 -->
<context:annotation-config/>
<!-- 添加自動掃描 -->
<context:component-scan base-package="com.lkt.entity.*"></context:component-scan>
<!-- 添加面向切面功能 -->
<aop:aspectj-autoproxy/>
</beans>
然後寫一個普通的接口
package com.lkt.entity.aspectj;
public interface IArithmeticCalculator {
public double add(double a, double b);
public double sub(double a, double b);
public double mul(double a, double b);
public double div(double a, double b);
}
寫實現接口的類,添加Spring的組件註解,可以讓Spring自動掃描到
package com.lkt.entity.aspectj;
import org.springframework.stereotype.Component;
@Component
public class ArithmeticCalculator implements IArithmeticCalculator {
@Override
public double add(double a,double b){
System.out.println("加法運算:"+(a+b));
return a+b;
}
@Override
public double sub(double a, double b) {
System.out.println("減法運算:"+(a-b));
return a-b;
}
@Override
public double mul(double a, double b) {
System.out.println("乘法運算:"+(a*b));
return a*b;
}
@Override
public double div(double a, double b) {
System.out.println("除法運算:"+(a/b));
return a/b;
}
}
然後編寫一個aspect類,用來對ArithmeticCalculator進行前置和後置通知
package com.lkt.entity.aspectj;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;
@Component
@Aspect
public class LogTest {
@Before("execution(* IArithmeticCalculator.add(..))")
public void logBefore(){
System.out.println("前置通知");
}
@AfterReturning("execution(* IArithmeticCalculator.add(..))")
public void logAfter(){
System.out.println("後置通知");
}
}
@Aspect表示爲一個aspect類,@Before("execution(* IArithmeticCalculator.add(..))"),表示執行IArithmeticCalculator的add方法之前要執行這個方法,@AfterReturning爲執行結束後再執行這個方法,*代表任何修飾符,後面的兩個點表示任何數量的參數
然後我們在執行add方法的時候就會打印
前置通知
加法運算:2.0
後置通知
如果你想在執行切入方法時,想知道是執行哪個方法時調用到該切入方法的,你可以使用JoinPoint這個對象實例。
後置通知中可以在@AfterReturning註解中添加一個returning屬性,訪問連接點的返回值,用於傳入返回值。
package com.lkt.entity.aspectj;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;
@Component
@Aspect
public class LogTest {
@Before("execution(* IArithmeticCalculator.*(..))")
public void logBefore(JoinPoint jp){
String name=jp.getSignature().getName();
System.out.println("前置通知,方法"+name);
}
@AfterReturning(pointcut="execution(* IArithmeticCalculator.*(..))",returning="result")
public void logAfterReturning(JoinPoint jp,Object result){
String name=jp.getSignature().getName();
System.out.println("後置通知,方法:"+name+",返回值:"+result);
}
@After("execution(* IArithmeticCalculator.*(..))")
public void logAfter(JoinPoint jp){
System.out.println("最終通知");
}
}
如果感覺每次都要定義重複的切入點很麻煩時,AspectJ也提供獨立定義切入點,在多個通知中重用
package com.lkt.entity.aspectj;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;
@Component
@Aspect
public class LogTest {
@Pointcut("execution(* IArithmeticCalculator.*(..))")
private void logginOperation(){};
@Before("logginOperation()")
public void logBefore(JoinPoint jp){
String name=jp.getSignature().getName();
System.out.println("前置通知,方法"+name);
}
@AfterReturning(pointcut="logginOperation()",returning="result")
public void logAfterReturning(JoinPoint jp,Object result){
String name=jp.getSignature().getName();
System.out.println("後置通知,方法:"+name+",返回值:"+result);
}
@After("logginOperation()")
public void logAfter(JoinPoint jp){
System.out.println("最終通知");
}
}
這樣每次寫切入點的時候,就可以使用logginOperation()了