结构型设计

AuthMiddleware.java

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+package middleware;
+
+/**
+ * 认证中间件装饰器
+ * 具体装饰器类，用于验证请求的认证信息
+ */
+public class AuthMiddleware extends MiddlewareDecorator {
+    
+    public AuthMiddleware(HttpRequestHandler decoratedHandler) {
+        super(decoratedHandler);
+    }
+    
+    @Override
+    public HttpResponse handle(HttpRequest request) {
+        // 简单的认证检查逻辑
+        String authHeader = request.getHeaders();
+        if (authHeader != null && authHeader.contains("Authorization: Bearer token123")) {
+            System.out.println("Authentication successful");
+            return super.handle(request);
+        } else {
+            HttpResponse response = new HttpResponse();
+            response.setStatusCode(401);
+            response.setBody("Unauthorized");
+            return response;
+        }
+    }
+}

BasicHttpRequestHandler.java

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+package middleware;
+
+/**
+ * 基本的HTTP请求处理器实现
+ * 装饰器模式中的具体组件类
+ */
+public class BasicHttpRequestHandler implements HttpRequestHandler {
+    @Override
+    public HttpResponse handle(HttpRequest request) {
+        HttpResponse response = new HttpResponse();
+        response.setBody("Hello from Basic Handler: " + request.getPath());
+        response.setHeaders("Content-Type: text/plain");
+        return response;
+    }
+}

CORSMiddleware.java

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+package middleware;
+
+/**
+ * CORS中间件装饰器
+ * 具体装饰器类，用于处理跨域资源共享请求
+ */
+public class CORSMiddleware extends MiddlewareDecorator {
+    
+    public CORSMiddleware(HttpRequestHandler decoratedHandler) {
+        super(decoratedHandler);
+    }
+    
+    @Override
+    public HttpResponse handle(HttpRequest request) {
+        HttpResponse response = super.handle(request);
+        
+        // 添加CORS头信息
+        String existingHeaders = response.getHeaders() != null ? response.getHeaders() + "\n" : "";
+        response.setHeaders(existingHeaders + "Access-Control-Allow-Origin: *\nAccess-Control-Allow-Methods: GET, POST, PUT, DELETE\nAccess-Control-Allow-Headers: *");
+        
+        return response;
+    }
+}

HttpRequest.java

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+package middleware;
+
+/**
+ * HTTP请求对象
+ */
+public class HttpRequest {
+    private String path;
+    private String method;
+    private String headers;
+    private String body;
+    
+    public HttpRequest(String path, String method) {
+        this.path = path;
+        this.method = method;
+    }
+    
+    public String getPath() {
+        return path;
+    }
+    
+    public String getMethod() {
+        return method;
+    }
+    
+    public void setHeaders(String headers) {
+        this.headers = headers;
+    }
+    
+    public String getHeaders() {
+        return headers;
+    }
+    
+    public void setBody(String body) {
+        this.body = body;
+    }
+    
+    public String getBody() {
+        return body;
+    }
+}

HttpRequestHandler.java

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+package middleware;
+
+/**
+ * HTTP请求处理器接口
+ * 装饰器模式的核心组件，定义了处理HTTP请求的方法
+ */
+public interface HttpRequestHandler {
+    /**
+     * 处理HTTP请求并返回响应
+     * @param request HTTP请求对象
+     * @return HTTP响应对象
+     */
+    HttpResponse handle(HttpRequest request);
+}

HttpResponse.java

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+package middleware;
+
+/**
+ * HTTP响应对象
+ */
+public class HttpResponse {
+    private int statusCode;
+    private String headers;
+    private String body;
+    
+    public HttpResponse() {
+        this.statusCode = 200;
+    }
+    
+    public int getStatusCode() {
+        return statusCode;
+    }
+    
+    public void setStatusCode(int statusCode) {
+        this.statusCode = statusCode;
+    }
+    
+    public void setHeaders(String headers) {
+        this.headers = headers;
+    }
+    
+    public String getHeaders() {
+        return headers;
+    }
+    
+    public void setBody(String body) {
+        this.body = body;
+    }
+    
+    public String getBody() {
+        return body;
+    }
+}

LoggingMiddleware.java

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+package middleware;
+
+/**
+ * 日志中间件装饰器
+ * 具体装饰器类，用于记录请求信息
+ */
+public class LoggingMiddleware extends MiddlewareDecorator {
+    
+    public LoggingMiddleware(HttpRequestHandler decoratedHandler) {
+        super(decoratedHandler);
+    }
+    
+    @Override
+    public HttpResponse handle(HttpRequest request) {
+        System.out.println("Logging request: " + request.getMethod() + " " + request.getPath());
+        HttpResponse response = super.handle(request);
+        System.out.println("Logging response status: " + response.getStatusCode());
+        return response;
+    }
+}

MiddlewareDecorator.java

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+package middleware;
+
+/**
+ * 中间件装饰器抽象类
+ * 装饰器模式中的装饰器类，实现了HttpRequestHandler接口并持有一个HttpRequestHandler引用
+ */
+public abstract class MiddlewareDecorator implements HttpRequestHandler {
+    protected HttpRequestHandler decoratedHandler;
+    
+    public MiddlewareDecorator(HttpRequestHandler decoratedHandler) {
+        this.decoratedHandler = decoratedHandler;
+    }
+    
+    @Override
+    public HttpResponse handle(HttpRequest request) {
+        return decoratedHandler.handle(request);
+    }
+}