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深度解析责任链Filter模式：构建灵活可扩展的请求处理管道

java 2025/5/6 11:46:28

一、责任链Filter模式：Web请求的「流水线」处理

1.1 什么是责任链Filter模式？

责任链Filter模式是一种通过链式结构组织多个处理器（Filter），依次处理请求的设计模式。每个Filter都能：

拦截请求：在请求到达目标前进行预处理
处理响应：在响应返回客户端前进行后处理
动态编排：灵活调整处理顺序和逻辑

典型应用场景：
✅ 用户身份认证
✅ 请求日志记录
✅ 数据加密/解密
✅ 接口限流熔断

二、Servlet Filter原理解析

2.1 Servlet Filter执行流程

2.2 核心接口解析

public interface Filter {void init(FilterConfig config);  // 初始化void doFilter(ServletRequest request, ServletResponse response,FilterChain chain); // 核心处理void destroy();                  // 销毁
}

三、Spring Security过滤器链实战 🔐

3.1 安全过滤器链结构

http.addFilterBefore(new LogFilter(), BasicAuthenticationFilter.class).addFilterAfter(new CorsFilter(), SecurityContextPersistenceFilter.class).authorizeRequests().anyRequest().authenticated();

3.2 自定义Filter示例

public class JwtFilter extends OncePerRequestFilter {@Overrideprotected void doFilterInternal(HttpServletRequest request,HttpServletResponse response,FilterChain chain) throws IOException, ServletException {String token = parseToken(request);if (validateToken(token)) {SecurityContextHolder.getContext().setAuthentication(...);}chain.doFilter(request, response); // 继续执行链}
}

四、手写轻量级Filter框架

4.1 定义Filter接口

public interface MyFilter {void doFilter(Request request, Response response,FilterChain chain);
}public class FilterChain {private List<MyFilter> filters = new ArrayList<>();private int index = 0;public FilterChain addFilter(MyFilter filter) {filters.add(filter);return this;}public void doFilter(Request request, Response response) {if (index < filters.size()) {MyFilter filter = filters.get(index++);filter.doFilter(request, response, this);}}
}

4.2 实现具体Filter

public class LogFilter implements MyFilter {@Overridepublic void doFilter(Request request, Response response,FilterChain chain) {System.out.println("请求开始: " + request.getUrl());chain.doFilter(request, response);System.out.println("响应状态: " + response.getStatus());}
}public class AuthFilter implements MyFilter {@Overridepublic void doFilter(Request request, Response response,FilterChain chain) {if (!checkToken(request)) {response.setStatus(401);return; // 中断链}chain.doFilter(request, response);}
}

五、责任链模式的六大设计技巧

5.1 动态调整Filter顺序

Collections.swap(filters, 0, 1); // 交换前两个Filter

5.2 条件跳过滤

public void doFilter(Request request, Response response,FilterChain chain) {if (shouldSkip(request)) {chain.doFilter(request, response); // 跳过当前Filter} else {// 执行处理逻辑}
}

5.3 性能优化方案

缓存Filter实例：避免重复创建
并行处理：对无依赖的Filter使用多线程
短路机制：及时终止无效请求

六、企业级应用场景

6.1 全链路日志追踪

public class TraceFilter implements Filter {@Overridepublic void doFilter(...) {MDC.put("traceId", UUID.randomUUID().toString());chain.doFilter(request, response);MDC.clear();}
}

6.2 API限流控制

public class RateLimitFilter implements Filter {private RateLimiter limiter = RateLimiter.create(100); // 100QPS@Overridepublic void doFilter(...) {if (!limiter.tryAcquire()) {response.sendError(429);return;}chain.doFilter(request, response);}
}

七、常见问题解决方案

问题	现象	解决方案
Filter顺序错误	安全Filter未优先执行	调整@Order或注册顺序
内存泄漏	Filter未正确释放资源	实现destroy()方法清理资源
性能瓶颈	Filter链过长	合并轻量级Filter，异步处理
循环调用	chain.doFilter缺失	确保每个Filter正确传递链
异常处理遗漏	Filter未捕获异常	添加try-catch块统一处理

八、源码级调试技巧

8.1 Servlet Filter调试

// 关键断点位置
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter()
org.apache.catalina.core.ApplicationFilterChain.doFilter()

8.2 Spring Security调试

// 观察过滤器链构建过程
org.springframework.security.config.annotation.web.builders.HttpSecurity.addFilter()
org.springframework.security.web.DefaultSecurityFilterChain