Cglib agent - Code enhancement test

Guide pack

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.3.0</version>
</dependency>

Write method interceptors

• Method to enhance specific logic

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;
import java.util.Arrays;

/** *  Customize  cglib  agent  * * @author Ara * @since 2022/6/20 */
public class MyCglibProxyMethodInterceptor<T> implements MethodInterceptor {
    

    /** *  Target audience  */
    private final T target;

    /** *  Construction method  */
    public MyCglibProxyMethodInterceptor(T target) {
    
        this.target = target;
    }

    /** *  Get proxy object  */
    public T getProxyObject(){
    
        Enhancer enhancer = new Enhancer();
        // Set parent class   because cglib Is to generate a subclass for the specified class to enhance its behavior 
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);
        return (T) enhancer.create();
    }

    // TODO  Perform the enhancement 
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
    
        System.out.println(" Before execution   Method parameter : " + Arrays.toString(objects));

        Object result = method.invoke(target, objects);

        System.out.println(" After execution   Return value : " + result);

        return result;
    }
}

Write the test class to be enhanced

• Enhance target points

/** *  article  Service * * @author Ara * @since 2022/6/20 */
public class ArticleService {
    

    public String saveArticle(String article) {
    
        System.out.printf(" Save the article [%s]...%n", article);
        return article;
    }

}

Write tests

• Check whether it can be enhanced

public class MainTest {
    
    public static void main(String[] args) {
    
        ArticleService articleService = new ArticleService();
        // Statement Cglib Method intercept enhanced implementation class 
        MyCglibProxyMethodInterceptor<ArticleService> cglibProxyMethodInterceptor = new MyCglibProxyMethodInterceptor<>(articleService);
        //  Get proxy class 
        ArticleService articleServiceProxy = cglibProxyMethodInterceptor.getProxyObject();

        // Use proxy classes to call methods 
        articleServiceProxy.saveArticle("Java");
    }
}

The verification results

A small summary

Simple comparison cglib And JDK A dynamic proxy ：

• Use here cglib When acting , Whether or not the target class implements the interface , Can be enhanced .
• But when used alone JDK A dynamic proxy , You can only enhance the methods of class overrides that implement interfaces .

Blogger JDK Links to articles about dynamic agents

The following is right cglib and JDK Whether dynamic proxy can enhance the comparison code of classes with and without interface implementation , Interested readers can test ：

public class MainTest {
    
    public static void main(String[] args) {
    
        cglibProxyNoInterfaceTest();
    }

    /** * cglib agent ( Proxy target class does not implement interface ) */
    private static void cglibProxyNoInterfaceTest(){
    
        ArticleService articleService = new ArticleService();
        // Statement Cglib Method intercept enhanced implementation class 
        MyCglibProxyMethodInterceptor<ArticleService> cglibProxyMethodInterceptor = new MyCglibProxyMethodInterceptor<>(articleService);
        //  Get proxy class 
        ArticleService articleServiceProxy = cglibProxyMethodInterceptor.getProxyObject();

        // Use proxy classes to call methods 
        articleServiceProxy.saveArticle("Java");
    }

    /** * cglib agent ( The proxy target class implements the interface ) */
    private static void cglibProxyHasInterfaceTest(){
    
        UserService userService = new UserServiceImpl();
        // Statement Cglib Method intercept enhanced implementation class 
        MyCglibProxyMethodInterceptor<UserService> cglibProxyMethodInterceptor = new MyCglibProxyMethodInterceptor<>(userService);
        //  Get proxy class 
        UserService userServiceProxy = cglibProxyMethodInterceptor.getProxyObject();

        // Use proxy classes to call methods 
        userServiceProxy.add("Ara");
    }

    /** * JDK A dynamic proxy ( The proxy target class implements the interface ) */
    private static void jdkDynamicProxyHasInterfaceTest(){
    
        // The original object  ( Interface receive parameters )
        UserService userService = new UserServiceImpl();

        // Declare enhanced handlers 
        MyJdkProxyInvocationHandler<UserService> proxyInvocationHandler = new MyJdkProxyInvocationHandler<>(userService);
        // Get proxy object 
        UserService proxyUserService = proxyInvocationHandler.getProxyObject();

        // Use proxy objects to call methods 
        proxyUserService.add("Ara");
    }

    /** * JDK A dynamic proxy ( Proxy target class does not implement interface ) *  Mistake , Use JDK Dynamic proxy implementation enhancements , The proxy target must be required to implement the interface  */
    private static void jdkDynamicProxyNoInterfaceTest(){
    
        ArticleService articleService = new ArticleService();

        // Declare enhanced handlers 
        MyJdkProxyInvocationHandler<ArticleService> proxyInvocationHandler = new MyJdkProxyInvocationHandler<>(articleService);
        // Get proxy object 
        ArticleService proxyArticleService = proxyInvocationHandler.getProxyObject();

        // Use proxy objects to call methods 
        proxyArticleService.saveArticle("Java");
    }
}