Java 静态代理 vs 动态代理 vs CGLib Proxy

不念不忘少年蓝@ 2022-06-04 02:25 180阅读 0赞

代理：为其他对象提供访问目标对象的一种控制或机制。

### **接口定义** ###

public interface FontProvider {
        Font getFont(String name);
    }

### **实现定义** ###

@Slf4j
    public class FontProviderImpl implements FontProvider { 
    
        public FontProviderImpl() {
            log.info("FontProviderImpl Constructor");
        }
    
        @Override
        public Font getFont(String name) {
            log.info("ready to call getFont()");
            return new Font(name, Font.ITALIC, 18);
        }
    }

### **代理定义** ###

*  **静态代理**

@Slf4j
    public class FontProviderSimpleProxy implements FontProvider { 
        private FontProvider fontProvider;
    
        public FontProviderSimpleProxy(FontProvider fontProvider) {
            this.fontProvider = fontProvider;
        }
    
        public Font getFont(String name) {
            log.info("ready to call getFont in FontProviderSimpleProxy, args is {}", name);
            return fontProvider.getFont(name);
        }
    }

*  **JDK动态代理**

@Slf4j
    public class FontProviderDynamicProxy implements InvocationHandler { private Object target; public FontProviderDynamicProxy(Object target) { this.target = target; }
    
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { log.info("ready to call getFont in FontProviderDynamicProxy, args is {}", args);
            Type[] types = method.getParameterTypes();
            if (method.getName().matches("get.+") && (types.length == 1) && (types[0] == String.class)) { return method.invoke(target, args); } return method.invoke(target, args);
        }
    }

*  **CGLib动态代理**

@Slf4j
    public class FontProviderCGLibProxy implements MethodInterceptor { 
        public <T> T getProxy(Class<T> cls) {
            return (T) Enhancer.create(cls, this);
        }
    
        @Override
        public Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
            log.info("ready to call getFont in FontProviderCGLibProxy, args is {}", args);
            Object result = methodProxy.invokeSuper(o, args);
            log.info("proxy method result is {}", result);
            return result;
        }
    }

### **抽象代理工厂** ###

public interface ProviderFactory {
        FontProvider getFontProviderStaticProxy();
        FontProvider getFontProviderDynamicProxy();
        FontProvider getFontProviderCGlibProxy();
    }

### **工厂方法实现** ###

@Slf4j
    public class ProviderFactoryImpl implements ProviderFactory { 
        @Override
        public FontProvider getFontProviderStaticProxy() {
            log.info("Get FontProvider by Simple Proxy");
            return new FontProviderSimpleProxy(new FontProviderImpl());
        }
    
        @Override
        public FontProvider getFontProviderDynamicProxy() {
            log.info("Get FontProvider by JDK Dynamic Proxy");
            Class<FontProvider> targetClass = FontProvider.class;
            return (FontProvider) Proxy.newProxyInstance(targetClass.getClassLoader(),
                    new Class[]{targetClass},
                    new FontProviderDynamicProxy(new FontProviderImpl()));
        }
    
        @Override
        public FontProvider getFontProviderCGlibProxy() {
            log.info("Get FontProvider by CGLib Proxy");
            FontProviderCGLibProxy fontProviderCGLibProxy = new FontProviderCGLibProxy();
            FontProvider fontProvider = fontProviderCGLibProxy.getProxy(FontProviderImpl.class);
            return fontProvider;
        }
    
    }

### **方法调用** ###

@Slf4j
    public class ProxyEntry {
        public static void main(String[] args) {
            ProviderFactoryImpl providerFactoryImpl = new ProviderFactoryImpl();
            FontProvider fontProviderStaticProxy = providerFactoryImpl.getFontProviderStaticProxy();
            log.info("{}", fontProviderStaticProxy.getFont("Microsoft YaHei"));
            log.info("***********************************************");
            FontProvider fontProviderDynamicProxy = providerFactoryImpl.getFontProviderDynamicProxy();
            log.info("{}", fontProviderDynamicProxy.getFont("微软雅黑"));
            log.info("***********************************************");
            FontProvider fontProviderCGlibProxy = providerFactoryImpl.getFontProviderCGlibProxy();
            log.info("{}", fontProviderCGlibProxy.getFont("微软雅黑"));
        }
    }

### **JDK 动态代理 vs CGLib Proxy** ###

*  JDK动态代理只能通过接口来代理，因此，目标委托类需要实现一个接口，代理类也需要同时实现该接口。
 *  CGLIB可以通过子类创建代理，在这种应用场景下，代理类成为目标类的子类，不需要接口。

![这里写图片描述][SouthEast]

### **EnableAspectJAutoProxy** ###

Spring中添加@EnableAspectJAuotProxy注解用以支持@AspectJ自动代理

> @EnableAspectJAutoProxy(proxyTargetClass=true)

强制Spring 容器使用CGLib代理，而非默认的基于接口的JDK动态代理方式。

[https://stackoverflow.com/questions/10664182/what-is-the-difference-between-jdk-dynamic-proxy-and-cglib][https_stackoverflow.com_questions_10664182_what-is-the-difference-between-jdk-dynamic-proxy-and-cglib]  
[https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/EnableAspectJAutoProxy.html][https_docs.spring.io_spring_docs_current_javadoc-api_org_springframework_context_annotation_EnableAspectJAutoProxy.html]

[SouthEast]: /images/20220604/1487633471e243199d2648a491df57f6.png
[https_stackoverflow.com_questions_10664182_what-is-the-difference-between-jdk-dynamic-proxy-and-cglib]: https://stackoverflow.com/questions/10664182/what-is-the-difference-between-jdk-dynamic-proxy-and-cglib
[https_docs.spring.io_spring_docs_current_javadoc-api_org_springframework_context_annotation_EnableAspectJAutoProxy.html]: https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/EnableAspectJAutoProxy.html