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ahucoderahucoder
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The Proxy Pattern
1 parent f0087f3 commit 51bdbe2

17 files changed

+305
-9
lines changed

‎pom.xml‎

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<maven.compiler.release>21</maven.compiler.release>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<junit.version>5.8.2</junit.version>
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<lombok.version>1.18.36</lombok.version>
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<spring-boot-starter-web.version>3.4.5</spring-boot-starter-web.version>
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<guava.version>33.4.0-jre</guava.version>
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<commons-lang3.version>3.12.0</commons-lang3.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<version>1.18.36</version>
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<version>${lombok.version}</version>
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<scope>provided</scope>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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<version>3.4.5</version>
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<version>${spring-boot-starter-web.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>33.4.0-jre</version>
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<version>${guava.version}</version>
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</dependency>
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<!-- JUnit 5 -->
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<dependency>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-lang3</artifactId>
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<version>3.12.0</version>
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<version>${commons-lang3.version}</version>
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<scope>test</scope>
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</dependency>
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</dependencies>

‎src/main/java/proxy/dynamicproxy/App.java‎

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package proxy.dynamicproxy;
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import proxy.service.OrderService;
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import java.math.BigDecimal;
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public class App {
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public static void main(String[] args) {
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// jdk dynamic proxy
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OrderService proxy = new OrderServiceJdkProxyFactory().createProxy();
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proxy.createOrder("user123", "prod456", new BigDecimal("199.99"));
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System.out.println();
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proxy.cancelOrder("order789");
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System.out.println("========================================================");
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// cglib dynamic proxy
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proxy = new OrderServiceCglibProxyFactory().createProxy();
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proxy.createOrder("user123", "prod456", new BigDecimal("199.99"));
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System.out.println();
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proxy.cancelOrder("order789");
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}
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}

‎src/main/java/proxy/dynamicproxy/OrderServiceCglibProxyFactory.java‎

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package proxy.dynamicproxy;
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import org.springframework.cglib.proxy.Enhancer;
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import org.springframework.cglib.proxy.MethodInterceptor;
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import org.springframework.cglib.proxy.MethodProxy;
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import proxy.service.AuthService;
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import proxy.service.LogService;
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import proxy.service.OrderService;
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import proxy.service.impl.AuthServiceImpl;
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import proxy.service.impl.LogServiceImpl;
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import proxy.service.impl.OrderServiceImpl;
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import java.lang.reflect.Method;
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public class OrderServiceCglibProxyFactory {
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private final OrderService orderService;
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private final AuthService authService;
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private final LogService logService;
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private final OrderServiceProxyProcess orderServiceProxyProcess;
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public OrderServiceCglibProxyFactory() {
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this.orderService = new OrderServiceImpl();
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this.authService = new AuthServiceImpl();
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this.logService = new LogServiceImpl();
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this.orderServiceProxyProcess = new OrderServiceProxyProcess();
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}
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public OrderService createProxy() {
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Enhancer enhancer = new Enhancer();
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enhancer.setSuperclass(orderService.getClass());
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enhancer.setCallback(new OrderServiceMethodInterceptor());
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return (OrderService) enhancer.create();
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}
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private class OrderServiceMethodInterceptor implements MethodInterceptor {
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@Override
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public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
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// before
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orderServiceProxyProcess.processBefore(method, args, authService, logService);
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// invoke real objects
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Object result = proxy.invokeSuper(obj, args);
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// after
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orderServiceProxyProcess.processAfter(method, args, authService, logService);
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return result;
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}
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}
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}

‎src/main/java/proxy/dynamicproxy/OrderServiceJdkProxyFactory.java‎

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package proxy.dynamicproxy;
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import proxy.service.AuthService;
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import proxy.service.LogService;
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import proxy.service.OrderService;
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import proxy.service.impl.AuthServiceImpl;
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import proxy.service.impl.LogServiceImpl;
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import proxy.service.impl.OrderServiceImpl;
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import java.lang.reflect.InvocationHandler;
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import java.lang.reflect.Method;
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import java.lang.reflect.Proxy;
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public class OrderServiceJdkProxyFactory {
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private final OrderService orderService;
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private final AuthService authService;
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private final LogService logService;
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private final OrderServiceProxyProcess orderServiceProxyProcess;
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public OrderServiceJdkProxyFactory() {
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this.orderService = new OrderServiceImpl();
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this.authService = new AuthServiceImpl();
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this.logService = new LogServiceImpl();
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this.orderServiceProxyProcess = new OrderServiceProxyProcess();
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}
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public OrderService createProxy() {
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return (OrderService) Proxy.newProxyInstance(
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orderService.getClass().getClassLoader(),
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orderService.getClass().getInterfaces(),
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new OrderServiceInvocationHandler()
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);
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}
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private class OrderServiceInvocationHandler implements InvocationHandler {
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@Override
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public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
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// before
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orderServiceProxyProcess.processBefore(method, args, authService, logService);
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// invoke real objects
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Object result = method.invoke(orderService, args);
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// after
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orderServiceProxyProcess.processAfter(method, args, authService, logService);
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return result;
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}
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}
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}

‎src/main/java/proxy/dynamicproxy/OrderServiceProxyProcess.java‎

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package proxy.dynamicproxy;
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import proxy.service.AuthService;
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import proxy.service.LogService;
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import java.lang.reflect.Method;
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public class OrderServiceProxyProcess {
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public void processBefore(Method method, Object[] args, AuthService authService, LogService logService) {
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String methodName = method.getName();
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if ("createOrder".equals(methodName)) {
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String userId = (String) args[0];
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authService.checkPermission(userId, "CREATE_ORDER");
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logService.log("Begin to create order", userId, (String) args[1], args[2].toString());
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} else if ("cancelOrder".equals(methodName)) {
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String orderId = (String) args[0];
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String userId = getUserIdByOrderId(orderId);
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authService.checkPermission(userId, "CANCEL_ORDER");
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logService.log("Start canceling orders", userId, orderId);
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}
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}
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public void processAfter(Method method, Object[] args, AuthService authService, LogService logService) {
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String methodName = method.getName();
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if ("createOrder".equals(methodName)) {
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String userId = (String) args[0];
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logService.log("Order creation completed", userId, (String) args[1], args[2].toString());
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} else if ("cancelOrder".equals(methodName)) {
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String orderId = (String) args[0];
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String userId = getUserIdByOrderId(orderId);
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logService.log("Order cancellation completed", userId, orderId);
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}
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}
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private String getUserIdByOrderId(String orderId) {
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return STR."user_\{orderId.hashCode()}"; // Mock
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}
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}

‎src/main/java/proxy/service/AuthService.java‎

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package proxy.service;
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public interface AuthService {
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void checkPermission(String userId, String permission);
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}

‎src/main/java/proxy/service/LogService.java‎

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package proxy.service;
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public interface LogService {
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void log(String action, String... params);
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}

‎src/main/java/proxy/service/OrderService.java‎

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package proxy.service;
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import java.math.BigDecimal;
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public interface OrderService {
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void createOrder(String userId, String productId, BigDecimal amount);
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void cancelOrder(String orderId);
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}

‎src/main/java/proxy/service/impl/AuthServiceImpl.java‎

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package proxy.service.impl;
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import proxy.service.AuthService;
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public class AuthServiceImpl implements AuthService {
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@Override
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public void checkPermission(String userId, String permission) {
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System.out.printf("[validate permission] user[%s] permission[%s]\n", userId, permission);
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//do sth...
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}
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}

‎src/main/java/proxy/service/impl/LogServiceImpl.java‎

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package proxy.service.impl;
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import proxy.service.LogService;
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import java.util.Arrays;
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public class LogServiceImpl implements LogService {
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@Override
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public void log(String action, String... params) {
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System.out.printf("[log record] operation[%s] params%s\n", action, Arrays.toString(params));
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}
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}

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