1. 创建两个类，增强类和被增强类，创建方法。

package com.demo.study_spring.aop.xml;

public class Book {

    public void buy() {
        System.out.println("buy ……");
    }
}

package com.demo.study_spring.aop.xml;

public class BookProxy {

    public void before() {
        System.out.println("before ……");
    }
}

2. 在spring配置文件中创建两个类对象。

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

        <!--创建两个类的对象-->
        <bean id="book" class="com.demo.study_spring.aop.xml.Book"></bean>
        <bean id="bookProxy" class="com.demo.study_spring.aop.xml.BookProxy"></bean>
</beans>

3. 在spring配置文件中配置切入点。

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

        <!--创建两个类的对象-->
        <bean id="book" class="com.demo.study_spring.aop.xml.Book"></bean>
        <bean id="bookProxy" class="com.demo.study_spring.aop.xml.BookProxy"></bean>

        <!--配置aop的增强-->
        <aop:config>
                <!--切入点-->
                <aop:pointcut id="p" expression="execution(* com.demo.study_spring.aop.xml.Book.buy(..))"/>

                <!--配置切面-->
                <aop:aspect ref="bookProxy">
                        <!--配置增强作用在具体的方法上-->
                        <aop:before method="before" pointcut-ref="p" />
                </aop:aspect>
        </aop:config>
</beans>