Java 代理模式

package proxydemo;// 账户服务实现类public class BankAccountImpl implements BankAccount {    @Override    public void viewBalance() {        System.out.println("Displaying account balance.");    }    @Override    public void withdraw() {        System.out.println("Withdrawing funds from account.");    }    @Override    public void deposit() {        System.out.println("Depositing funds into account.");    }}

package proxydemo;// 账户服务代理类// 代理类负责控制对实际账户服务操作的访问。只有管理员角色才能执行// withdraw()、deposit()和 transfer()操作，而普通用户只能查看余额// 和退出服务。public class BankAccountProxy implements BankAccount {    private BankAccountImpl BankAccount;    private String userRole;    // 构造方法，传入实际的账户服务对象和用户角色    public BankAccountProxy(BankAccountImpl BankAccount, String userRole) {        this.BankAccount = BankAccount;        this.userRole = userRole;        System.out.println("BankAccountProxy initialized with user role: " + userRole);    }    @Override    public void viewBalance() {        System.out.println("User with role " + userRole + " is viewing balance.");        BankAccount.viewBalance(); // 所有用户都可以查看余额    }    @Override    public void withdraw() {        if ("ADMIN".equals(userRole)) {            BankAccount.withdraw(); // 只有管理员可以取款        } else {            System.err.println("Access denied for user with role " + userRole + ": Only ADMIN can withdraw funds.");        }    }    @Override    public void deposit() {        if ("ADMIN".equals(userRole)) {            BankAccount.deposit(); // 只有管理员可以存款        } else {            System.err.println("Access denied for user with role " + userRole + ": Only ADMIN can deposit funds.");        }    }}

package proxydemo;public class Main {    public static void main(String[] args) {        BankAccountImpl BankAccount = new BankAccountImpl();        // 创建管理员用户的代理        System.out.println("Admin user:");        BankAccount adminProxy = new BankAccountProxy(BankAccount, "ADMIN");        adminProxy.viewBalance(); // 管理员可以查看余额        adminProxy.withdraw(); // 管理员可以取款        adminProxy.deposit(); // 管理员可以存款        // 创建普通用户的代理        System.out.println("\nRegular user:");        BankAccount userProxy = new BankAccountProxy(BankAccount, "USER");        userProxy.viewBalance(); // 普通用户可以查看余额        userProxy.withdraw(); // 普通用户无法取款        userProxy.deposit(); // 普通用户无法存款    }}

package proxydemo;import java.lang.reflect.Proxy;public class Main {    public static void main(String[] args) {        // 创建银行账户的真实对象        BankAccount realAccount = new BankAccountImpl();        // 创建代理对象        BankAccount proxyAccount = (BankAccount) JdkProxyFactory.getProxy(realAccount);        // 使用代理对象执行方法        proxyAccount.deposit(100);        proxyAccount.withdraw(50);        System.out.println("Balance: " + proxyAccount.getBalance());    }}class JdkProxyFactory {    public static Object getProxy(Object target) { // target: real object which implements BankAccount Interface        // 通过 Proxy 类创建动态代理对象        // 参数1：类加载器，通常使用目标对象的类加载器        // 参数2：目标对象实现的接口，可指定多个        // 参数3：InvocationHandler 实现类        return Proxy.newProxyInstance(                target.getClass().getClassLoader(),                target.getClass().getInterfaces(),                new BankAccountProxyHandler((BankAccount) target));    }}

import net.sf.cglib.proxy.MethodInterceptor;import net.sf.cglib.proxy.MethodProxy;import java.lang.reflect.Method;public class BankAccountInterceptor implements MethodInterceptor {    /**     * 拦截器方法     *     * @param proxyObj 代理对象     * @param method 被代理的方法     * @param args 方法的参数     * @param proxy 方法的代理对象，用于调用父类的方法     * @return 方法的返回值     * @throws Throwable 抛出的异常     */    @Override    public Object intercept(Object proxyObj, Method method, Object[] args, MethodProxy proxy) throws Throwable {        System.out.println("Method" + method.getName() + "is being called with arguments: " + java.util.Arrays.toString(args));        Object res = proxy.invoke(proxyObj, args);        System.out.println("Method" + method.getName() + "execution completed");        return res;    }}

import net.sf.cglib.proxy.Enhancer;public class Main {    public static void main(String[] args) {        // 创建动态代理类        Enhancer enhancer = new Enhancer();        enhancer.setSuperclass(BankAccount.class);        enhancer.setCallback(new BankAccountInterceptor());        // 创建代理对象        BankAccount proxyAccount = (BankAccount)enhancer.create();        // 通过代理对象调用方法        proxyAccount.deposit(100);        proxyAccount.withdraw(50);    }}