HandlerInterceptor介绍-笔记

1. HandlerInterceptor简介

org.springframework.web.servlet.HandlerInterceptor 是 Spring MVC 中用于拦截 HTTP 请求的核心接口。

public interface HandlerInterceptor {default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {return true;}default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {}default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {}
}

HandlerInterceptor 的核心方法介绍

preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
- 作用：在请求处理之前执行（即在控制器方法执行前）。
- 返回值：返回 true 表示继续后续处理；返回 false 表示中断请求（直接返回响应）。
- 典型用途：权限校验、请求日志记录。
postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
- 作用：在请求处理完成后、视图渲染之前执行。
- 参数说明：modelAndView 是控制器方法返回的结果。
- 典型用途：修改模型数据、记录响应日志。
afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
- 作用：在整个请求完成时执行（即视图渲染结束后）。
- 典型用途：资源清理、异常处理、性能统计。

它允许开发者在请求处理的不同阶段插入自定义逻辑，例如权限验证、日志记录、性能监控等。通过实现该接口的三个关键方法，可以灵活控制请求的处理流程。

2. 使用示例

2.1 日志拦截器demo

下面以一个日志拦截器为例，演示如何使用HandlerInterceptor。

`step1.`实现 `HandlerInterceptor` 接口

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.UUID;public class LoggingHandlerInterceptor implements HandlerInterceptor {// 请求处理前执行@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception {String requestId = UUID.randomUUID().toString();request.setAttribute("requestId", requestId);System.out.println("=== PreHandle ===");System.out.println("Request ID: " + requestId);System.out.println("Request URL: " + request.getRequestURL());return true; // 继续后续处理}// 请求处理后、视图渲染前执行@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,ModelAndView modelAndView) {System.out.println("=== PostHandle ===");if (modelAndView != null) {System.out.println("View Name: " + modelAndView.getViewName());return;}System.out.println("No view");}// 请求完成时执行@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,Exception ex) {System.out.println("=== AfterCompletion ===");if (ex != null) {System.out.println("Exception occurred: " + ex.getMessage());}System.out.println("Response Status: " + response.getStatus());System.out.println("Request ID: " + request.getAttribute("requestId"));}
}

step2.注册拦截器到 Spring MVC 配置

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;@Configuration
public class HandlerInterceptorWebConfig implements WebMvcConfigurer {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoggingHandlerInterceptor()).addPathPatterns("/**") // 拦截所有路径.excludePathPatterns("/public/**"); // 排除特定路径;}
}

step3.创建测试controller

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
public class HandlerInterceptorController {@GetMapping("HandlerInterceptorController/test")public String test() {return "test";}
}

step4. 测试

启动应用，浏览器输入 http://127.0.0.1:8080/HandlerInterceptorController/test ，日志输出如下：

2.2 其他使用场景demo

2.2.1 权限验证

在 preHandle 中检查用户是否登录，未登录则重定向到登录页面：

@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {if (userNotAuthenticated(request)) {response.sendRedirect("/login");return false; // 中断请求}return true;
}

2.2.2 性能监控

在 preHandle 记录开始时间，在 afterCompletion 计算耗时：

private Long startTime;@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {startTime = System.currentTimeMillis();return true;
}@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {long duration = System.currentTimeMillis() - startTime;System.out.println("Request took " + duration + " ms");
}