spring boot 拦截器例子

在Spring Boot中，拦截器是通过实现`HandlerInterceptor`接口来实现的。它允许你在请求到达控制器方法之前和之后执行自定义的逻辑。下面我将为你提供一个简单的Spring Boot拦截器的例子。

假设我们有一个简单的控制器类`UserController`，其中有两个请求处理方法：`getUser`和`saveUser`，我们希望在每次请求这两个方法前后记录日志。

1. 创建一个拦截器类 `LoggingInterceptor` 实现 `HandlerInterceptor` 接口：

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;public class LoggingInterceptor implements HandlerInterceptor {@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("Before handling request. URL: " + request.getRequestURL());return true; // Returning true allows the request to continue to the controller method. Returning false will stop the request.}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("After handling request. URL: " + request.getRequestURL());}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {// This method is called after the view rendering is complete.// It can be used for resource cleanup tasks.}
}

2. 在Spring Boot中注册拦截器，创建一个配置类`InterceptorConfig`：

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 InterceptorConfig implements WebMvcConfigurer {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoggingInterceptor());}
}

3. 创建一个简单的`UserController`：

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;@RestController
public class UserController {@GetMapping("/user")public String getUser(@RequestParam("id") String userId) {System.out.println("Getting user: " + userId);return "User: " + userId;}@PostMapping("/user")public String saveUser(@RequestParam("name") String username) {System.out.println("Saving user: " + username);return "Saved user: " + username;}
}

4. 运行Spring Boot应用，然后通过浏览器或者API请求测试：

当访问`http://localhost:8080/user?id=123`时，控制台输出：