Java Interceptor 拦截器如何实现请求合并

在Java中，拦截器（Interceptor）通常用于在方法调用前后执行一些操作，例如日志记录、权限检查等。要实现请求合并，我们可以在拦截器中缓存请求，然后在一定时间内合并相同的请求。以下是一个简单的示例，使用Java的动态代理实现拦截器，并实现请求合并功能：

1. 首先，创建一个接口Request，表示请求：

public interface Request {
    String getOperation();
    Object[] getParams();
}

2. 创建一个实现了Request接口的具体请求类：

public class ConcreteRequest implements Request {
    private String operation;
    private Object[] params;

    public ConcreteRequest(String operation, Object[] params) {
        this.operation = operation;
        this.params = params;
    }

    @Override
    public String getOperation() {
        return operation;
    }

    @Override
    public Object[] getParams() {
        return params;
    }
}

3. 创建一个RequestMerger类，用于合并请求：

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

public class RequestMerger {
    private final long mergeInterval;
    private final Map<String, Request> requestMap = new ConcurrentHashMap<>();

    public RequestMerger(long mergeInterval) {
        this.mergeInterval = mergeInterval;
    }

    public synchronized Request merge(Request request) {
        String key = request.getOperation() + Arrays.toString(request.getParams());
        Request existingRequest = requestMap.get(key);

        if (existingRequest == null) {
            requestMap.put(key, request);
            return request;
        } else {
            // 合并请求逻辑
            // ...
            return existingRequest;
        }
    }

    public synchronized void clearExpiredRequests() {
        long currentTime = System.currentTimeMillis();
        requestMap.entrySet().removeIf(entry -> currentTime - entry.getValue().getTimestamp() > mergeInterval);
    }
}

4. 创建一个拦截器类RequestMergeInterceptor：

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class RequestMergeInterceptor implements InvocationHandler {
    private final Object target;
    private final RequestMerger requestMerger;

    public RequestMergeInterceptor(Object target, long mergeInterval) {
        this.target = target;
        this.requestMerger = new RequestMerger(mergeInterval);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Request request = new ConcreteRequest(method.getName(), args);
        Request mergedRequest = requestMerger.merge(request);
        return method.invoke(target, mergedRequest.getParams());
    }

    public static Object createProxy(Object target, long mergeInterval) {
        return Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                new RequestMergeInterceptor(target, mergeInterval)
        );
    }
}

5. 使用拦截器：

public interface SomeService {
    void doSomething(String param);
}

public class SomeServiceImpl implements SomeService {
    @Override
    public void doSomething(String param) {
        System.out.println("执行操作: " + param);
    }
}

public class Main {
    public static void main(String[] args) {
        SomeService someService = new SomeServiceImpl();
        SomeService proxyService = (SomeService) RequestMergeInterceptor.createProxy(someService, 1000);

        proxyService.doSomething("请求1");
        proxyService.doSomething("请求1"); // 这个请求将被合并
        proxyService.doSomething("请求2");
    }
}

在这个示例中，我们创建了一个RequestMergeInterceptor拦截器，它可以将相同的请求合并。在RequestMerger类中，我们使用一个ConcurrentHashMap来存储请求，并在一定时间内合并相同的请求。这个示例仅用于演示目的，实际应用中可能需要根据具体需求进行调整。