Spring Boot 教程：拦截器

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

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：

观察以下代码以加深理解：

@Componentpublic 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：

@Componentpublic 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;@Componentpublic 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;@Componentpublic 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;@RestControllerpublic class ProductServiceController {   private static Map<String, Product> 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<Object> getProduct() {      return new ResponseEntity<>(productRepo.values(), HttpStatus.OK);   }}

       POJO 类文件 Product.java 如下：

package com.tutorialspoint.demo.model;public class Product {   private String id;   private String name;   public String getId() {      return id;   }   public void setId(String id) {      this.id = id;   }   public String getName() {      return name;   }   public void setName(String name) {      this.name = name;   }}

       主 Spring Boot 应用类文件 DemoApplication.java 如下所示：

package com.tutorialspoint.demo;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class DemoApplication {   public static void main(String[] args) {      SpringApplication.run(DemoApplication.class, args);      }}

       Maven build – pom.xml 文件在此：

<?xml version = "1.0" encoding = "UTF-8"?><project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "   http://www.w3.org/2001/XMLSchema-instance"   xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0   http://maven.apache.org/xsd/maven-4.0.0.xsd">      <modelVersion>4.0.0</modelVersion>   <groupId>com.tutorialspoint</groupId>   <artifactId>demo</artifactId>   <version>0.0.1-SNAPSHOT</version>   <packaging>jar</packaging>   <name>demo</name>   <description>Demo project for Spring Boot</description>   <parent>      <groupId>org.springframework.boot</groupId>      <artifactId>spring-boot-starter-parent</artifactId>      <version>1.5.8.RELEASE</version>      <relativePath/>   </parent>   <properties>      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>      <java.version>1.8</java.version>   </properties>   <dependencies>      <dependency>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-starter-web</artifactId>      </dependency>      <dependency>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-starter-test</artifactId>         <scope>test</scope>      </dependency>   </dependencies>   <build>      <plugins>         <plugin>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-maven-plugin</artifactId>         </plugin>      </plugins>   </build>   </project>

      Gradle Build build.gradle 文件在此：

buildscript {   ext {      springBootVersion = '1.5.8.RELEASE'   }   repositories {      mavenCentral()   }   dependencies {      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")   }}apply plugin: 'java'apply plugin: 'eclipse'apply plugin: 'org.springframework.boot'group = 'com.tutorialspoint'version = '0.0.1-SNAPSHOT'sourceCompatibility = 1.8repositories {   mavenCentral()}dependencies {   compile('org.springframework.boot:spring-boot-starter-web')   testCompile('org.springframework.boot:spring-boot-starter-test')}

      你可以使用下面的 Maven 或 Gradle 命令创建可执行的 JAR 文件，运行 Spring Boot 应用：

对于 Maven，使用以下命令：

mvn clean install

       在 “BUILD SUCCESS” 之后，你可以在 target 目录下找到 JAR 文件：

对于 Gradle，使用以下命令：

gradle clean build

       在 “BUILD SUCCESSFUL” 之后，你可以在 build/libs 目录下找到 JAR 文件：

可以使用以下命令运行 JAR 文件：

java –jar

此时，应用已经在 Tomcat 8080 端口启动了，如下所示：

在 POSTMAN 应用中单击以下 URL，你可以看到下面的结果：

GET API: [http://localhost:8080/products](http://localhost:8080/products): 


在控制台窗口，你可以看到加在拦截器中的 System.out.println 打印出来的结果，截屏如下：