Spring之AOP注解之引来通知

引入通知是一种特殊的通知类型。它通过为接口提供实现类，允许对象动态地实现接口，就像对象已经在运行时扩展了实现类一样。

引入通知可以使用两个实现类 MaxCalculator 和 MinCalculator， 让 PureCalculator动态地实现 IMaxCalculator 和 IMinCalculator 接口。 而这与从 MaxCalculator 和 MinCalculator中实现多继承的效果相同。但却不需要修改 PureCalculator的源代码。引入通知也必须在切面中声明，在切面中，通过为任意字段添加@DeclareParents 注解来引入声明。注解类型的 value 属性表示哪些类是当前引入通知的目标。value 属性值也可以是一个 AspectJ 类型的表达式，可以将一个接口引入到多个类中。defaultImpl 属性中指定这个接口使用的实现类。

示例

1. 添加模型接口和类

package xyz.huning.spring4.aop.calculator;

public interface ICalculator {

	double add(double x,double y);
	
	double sub(double x,double y);
	
	double mul(double x,double y);
	
	double div(double x,double y);	
	
}

package xyz.huning.spring4.aop.calculator;

public interface IMaxCalculator {

	double max(double x,double y);
	
}

package xyz.huning.spring4.aop.calculator;

public interface IMinCalculator {

	double min(double x,double y);
	
}

package xyz.huning.spring4.aop.calculator;

import org.springframework.stereotype.Component;

@Component
public class PureCalculator implements ICalculator {

	@Override
	public double add(double x, double y) {
		System.out.println("execute method add ...");
		return x + y;
	}

	@Override
	public double sub(double x, double y) {
		System.out.println("execute method sub ...");
		return x - y;
	}

	@Override
	public double mul(double x, double y) {
		System.out.println("execute method mul ...");
		return x * y;
	}

	@Override
	public double div(double x, double y) {
		System.out.println("execute method div ...");
		return x / y;
	}

}

package xyz.huning.spring4.aop.calculator.aopimport.annotation;

import xyz.huning.spring4.aop.calculator.IMaxCalculator;

public class MaxCalculator implements IMaxCalculator {

	@Override
	public double max(double x, double y) {
		System.out.println("execute max method ...");
		return x > y ? x : y;
	}

}

package xyz.huning.spring4.aop.calculator.aopimport.annotation;

import xyz.huning.spring4.aop.calculator.IMinCalculator;

public class MinCalculator implements IMinCalculator {

	@Override
	public double min(double x, double y) {
		System.out.println("execute min method ...");
		return x < y ? x : y;
	}

}

package xyz.huning.spring4.aop.calculator.aopimport.annotation;

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

import xyz.huning.spring4.aop.calculator.IMaxCalculator;
import xyz.huning.spring4.aop.calculator.IMinCalculator;

@Order(3)
@Aspect
@Component
public class CalculatorMaxMinAspect {

	@DeclareParents(value="* *.PureCalculator",defaultImpl=MaxCalculator.class)
	private IMaxCalculator maxCalculator;
	
	@DeclareParents(value="* *.PureCalculator",defaultImpl=MinCalculator.class)
	private IMinCalculator minCalculator;
	
}

2. 添加配置文件

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	
	<!--自定义bean扫描范围-->
	<context:component-scan base-package="xyz.huning.spring4.aop.calculator"></context:component-scan>
	
	<!--使Aspectj注解启作用-->
	<aop:aspectj-autoproxy></aop:aspectj-autoproxy>
	
</beans>

3. 添加测试类

package xyz.huning.spring4.aop.calculator.aopimport.annotation;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import xyz.huning.spring4.aop.calculator.IMaxCalculator;
import xyz.huning.spring4.aop.calculator.IMinCalculator;

public class Main {

	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("calculator-aop-annotation.xml");

		IMaxCalculator maxCalculator = ctx.getBean("pureCalculator", IMaxCalculator.class);
		maxCalculator.max(30, 40);
		IMinCalculator minCalculator = ctx.getBean("pureCalculator", IMinCalculator.class);
		minCalculator.min(30, 40);
		
		((ClassPathXmlApplicationContext)ctx).close();
	}
}

4. 执行结果