一文搞懂Java常见的三种代理模式(静态代理、动态代理和cglib代理)

public interface FileUploader {
    void upload(String file);
}

public class RealFileUploader implements FileUploader {
    @Override
    public void upload(String file) {
        // 实际的文件上传逻辑
        System.out.println("Uploading file: " + file);
    }
}

public class ProxyFileUploader implements FileUploader {
    private FileUploader realFileUploader;
    public ProxyFileUploader(FileUploader realFileUploader) {
        this.realFileUploader = realFileUploader;
    }
    @Override
    public void upload(String file) {
        // 额外的处理，比如记录日志
        System.out.println("Before uploading: " + file);
        // 调用真实主题的上传方法
        realFileUploader.upload(file);
        // 额外的处理，比如记录日志
        System.out.println("After uploading: " + file);
    }
}

public class Main {
    public static void main(String[] args) {
        // 创建真实主题
        FileUploader realFileUploader = new RealFileUploader();
        // 创建代理主题，并将真实主题传入
        FileUploader proxyFileUploader = new ProxyFileUploader(realFileUploader);
        // 通过代理主题进行文件上传
        proxyFileUploader.upload("example.txt");
    }
}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class DynamicProxyHandler implements InvocationHandler {
    private Object realObject;
    public DynamicProxyHandler(Object realObject) {
        this.realObject = realObject;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 额外的处理，比如记录日志
        System.out.println("Before invoking: " + method.getName());
        // 调用真实主题的对应方法
        Object result = method.invoke(realObject, args);
        // 额外的处理，比如记录日志
        System.out.println("After invoking: " + method.getName());
        return result;
    }
}

import java.lang.reflect.Proxy;
public class Main {
    public static void main(String[] args) {
        // 创建真实主题
        FileUploader realFileUploader = new RealFileUploader();
        // 创建动态代理的处理器
        InvocationHandler handler = new DynamicProxyHandler(realFileUploader);
        // 创建代理类
        FileUploader proxyFileUploader = (FileUploader) Proxy.newProxyInstance(
                FileUploader.class.getClassLoader(),
                new Class[]{FileUploader.class},
                handler
        );
        // 通过动态代理进行文件上传
        proxyFileUploader.upload("example.txt");
    }
}

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>版本号</version>
</dependency>

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
}

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CalculatorProxyGenerator implements MethodInterceptor {
    private Object target;
    public CalculatorProxyGenerator(Object target) {
        this.target = target;
    }
    public Object createProxy() {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);
        return enhancer.create();
    }
    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("Before invoking: " + method.getName());
        Object result = proxy.invokeSuper(obj, args);
        System.out.println("After invoking: " + method.getName());
        return result;
    }
}

public class Main {
    public static void main(String[] args) {
        Calculator calculator = new Calculator();
        CalculatorProxyGenerator proxyGenerator = new CalculatorProxyGenerator(calculator);
        Calculator proxyCalculator = (Calculator) proxyGenerator.createProxy();
        int result = proxyCalculator.add(3, 5);
        System.out.println("Result: " + result);
    }
}