Analysis of JDK dynamic proxy examples in java

1. Description

Java provides a dynamic proxy class Proxy. Proxy is not a class of what we call proxy objects, but provides a static method for creating proxy objects. Method (newProxyInstance) to obtain the proxy object.

2. Example

public class HelloWorld {
    public static void main(String[] args) {
        // 获取代理对象
        ProxyFactory factory = new ProxyFactory();
        
        SellTickets proxyObject = factory.getProxyObject();
        
        proxyObject.sell();
    }
}
 
// 卖票接口
interface SellTickets {
    void sell();
}
 
// 火车站，火车站具有卖票功能，所以需要实现SellTickets接口
class TrainStation implements SellTickets {
    @Override
    public void sell() {
        System.out.println("火车站卖票");
    }
}
 
// 代理工厂，用来创建代理对象
class ProxyFactory {
    private TrainStation station = new TrainStation();
 
    public SellTickets getProxyObject() {
        // 使用Proxy获取代理对象
 
        /**
         * newProxyInstance() 方法参数说明：
         *  ClassLoader loader: 类加载器，用于加载代理类，使用真实对象的类加载器即可
         *  Class<?>[] interfaces：真实对象所实现的接口，代理模式真实对象和代理对象实现相同的接口
         *  InvocationHandler h：代理对象的调用处理程序
         */
 
        SellTickets sellTickets = (SellTickets) Proxy.newProxyInstance(
                station.getClass().getClassLoader(),
                new InvocationHandler() {
                    /**
                     * InvocationHandle中invoke方法参数说明：
                     *  proxy：代理对象
                     *  method：对应于在代理对象上调用的方法的Method实例
                     *  args：代理对象调用接口方法是传递的实际参数
                     */
                    
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        System.out.println("代理点收取一些服务费用（JDK动态代理方法）");
                        
                        // 执行真实对象
                        Object result = method.invoke(station, args);
                        return result;
                    }
                });
        return sellTickets;
    }
}

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