spring boot 拦截器获取controller返回的数据_Spring Boot快速入门之（十三）： 拦截器...

【注】本文译自：https://www.tutorialspoint.com/spring_boot/spring_boot_interceptor.htm

在以下两种情况下，可以在 Spring Boot 中使用拦截器来执行操作：

• • 发送请求到控制器之前
  • 发送响应到客户端之前

譬如，可以使用拦截器在发送请求到控制器之前添加请求头，并在发送响应到客户端之前添加响应头。

要用拦截器，你需要创建 @Component 类，并且要实现 HandlerInterceptor 接口。

下面是使用拦截器要知道的三个方法：

• • preHandle() 方法：用于在发送请求到控制器之前执行操作。这个方法应当返回 true 以响应客户端。
  • postHandle() 方法：用于在发送响应到客户端之前执行操作。
  • afterCompletion() 方法： 用于在请求和响应完成之后执行操作。

观察以下代码以加深理解：

@Component
public class ProductServiceInterceptor implements HandlerInterceptor {
   @Override
   public boolean preHandle(
      HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
      
      return true;
   }
   @Override
   public void postHandle(
      HttpServletRequest request, HttpServletResponse response, Object handler,
      ModelAndView modelAndView) throws Exception {}
   
   @Override
   public void afterCompletion(HttpServletRequest request, HttpServletResponse response,
      Object handler, Exception exception) throws Exception {}
}

还要通过 WebMvcConfigurerAdapter 用 InterceptorRegistry 注册这个拦截器：

@Component
public class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter {
   @Autowired
   ProductServiceInterceptor productServiceInterceptor;

   @Override
   public void addInterceptors(InterceptorRegistry registry) {
      registry.addInterceptor(productServiceInterceptor);
   }
}

在下面给出的示例中，我们将要使用后面给出的 GET products API：

Interceptor 类文件 ProductServiceInterceptor.java 如下所示：

package com.tutorialspoint.demo.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

@Component
public class ProductServiceInterceptor implements HandlerInterceptor {
   @Override
   public boolean preHandle
      (HttpServletRequest request, HttpServletResponse response, Object handler)
      throws Exception {
      
      System.out.println("Pre Handle method is Calling");
      return true;
   }
   @Override
   public void postHandle(HttpServletRequest request, HttpServletResponse response,
      Object handler, ModelAndView modelAndView) throws Exception {
      
      System.out.println("Post Handle method is Calling");
   }
   @Override
   public void afterCompletion
      (HttpServletRequest request, HttpServletResponse response, Object
      handler, Exception exception) throws Exception {
      
      System.out.println("Request and Response is completed");
   }
}

Application Configuration 类文件把拦截器注册到 Interceptor Registry中，ProductServiceInterceptorAppConfig.java 文件如下：

package com.tutorialspoint.demo.interceptor;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Component
public class ProductServiceInterceptorAppConfig extends WebMvcConfigurerAdapter {
   @Autowired
   ProductServiceInterceptor productServiceInterceptor;

   @Override
   public void addInterceptors(InterceptorRegistry registry) {
      registry.addInterceptor(productServiceInterceptor);
   }
}

Controller 类文件 ProductServiceController.java 如下：

package com.tutorialspoint.demo.controller;

import java.util.HashMap;
import java.util.Map;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.tutorialspoint.demo.exception.ProductNotfoundException;
import com.tutorialspoint.demo.model.Product;

@RestController
public class ProductServiceController {
   private static Map productRepo = new HashMap<>();   
   static {      
      Product honey = new Product();
      honey.setId("1");
      honey.setName("Honey");
      productRepo.put(honey.getId(), honey);      
      Product almond = new Product();
      almond.setId("2");
      almond.setName("Almond");
      productRepo.put(almond.getId(), almond);      
   }
   @RequestMapping(value = "/products")
   public ResponseEntity