AOP aspect becomes - create enhanced class

illustrate

Spring uses enhanced classes to define horizontal logic, while Spring only supports method join points, and incremental classes also contain information on where to add cross-cutting code to the method. So the enhancement contains both the horizontal logic and the information of some connection points.

Types of

According to the position of the connection point of the enhancement in the target class method, it is divided into

1. pre-enhancement
2. rear boost
3. Surround enhancement
4. Exception throwing enhancement
5. Referral enhancement

pre-enhancement

Scenario: The waiter provides 2 services: welcoming customers, serving customers

package com.jihite;

public interface Waiter {
    void greetTo(String name);
    void serveTo(String name);
}

The new arrivals are as follows

package com.jihite;

public class NaiveWaiter implements Waiter{
    @Override
    public void greetTo(String name) {
        System.out.println("Greet to " + name);
    }

    @Override
    public void serveTo(String name) {
        System.out.println("Serve to " + name);
    }
}

The new waiter comes up to provide service, which is relatively vigorous. Before doing everything, he will say hello. The following defines the pre-enhanced class.

package com.jihite;
import org.springframework.aop.MethodBeforeAdvice;

import java.lang.reflect.Method;

public class GreetingBeforeAdvice implements MethodBeforeAdvice{
    @Override
    public void before(Method method, Object[] args, Object obj) throws Throwable {
        String clientName = (String)args[0];
        System.out.println("How are you! Mr." + clientName);
    }
}

Configure in Spring

Define beans.xml in src/main/resources

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="greetingBeforeAdvice" class="com.jihite.GreetingBeforeAdvice"/>
    <bean id="targetBefore" class="com.jihite.NaiveWaiter"/>
    <bean id="waiterBefore" class="org.springframework.aop.framework.ProxyFactoryBean"
          p:interceptorNames="greetingBeforeAdvice"
          p:target-ref="targetBefore"
          p:proxyTargetClass="true"
          />
</beans>

test

public class BeforeAdviceTest {
    private Waiter target;
    private BeforeAdvice advice;
    private ProxyFactory pf;

    @BeforeTest
    public void init() {
        target = new NaiveWaiter();
        advice = new GreetingBeforeAdvice();
        pf = new ProxyFactory();
        pf.setTarget(target);
        pf.addAdvice(advice);
    }
}

result

How are you! Mr.Jphn
Greet to Jphn
How are you! Mr.Tom
Serve to Tom

Other types of enhancement classes are similar to pre-enhancement, please refer to the code

code

Link