关于springboot: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

在以下两种状况下，能够在 Spring Boot 中应用拦截器来执行操作：

• 发送申请到控制器之前
• 发送响应到客户端之前

  譬如，能够应用拦截器在发送申请到控制器之前增加申请头，并在发送响应到客户端之前增加响应头。

  要用拦截器，你须要创立 @Component 类，并且要实现 HandlerInterceptor 接口。

  上面是应用拦截器要晓得的三个办法：

• preHandle() 办法：用于在发送申请到控制器之前执行操作。这个办法该当返回 true 以响应客户端。
• postHandle() 办法：用于在发送响应到客户端之前执行操作。
• afterCompletion() 办法： 用于在申请和响应实现之后执行操作。

  察看以下代码以加深了解：

@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); }}

在上面给出的示例中，咱们将要应用前面给出的 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;](http://org.springframework.stereotype.component%3b/)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 利用类文件 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](http://maven.apache.org/POM/4.0.0)" xmlns:xsi = " [http://www.w3.org/2001/XMLSchema-instance](http://www.w3.org/2001/XMLSchema-instance)" xsi:schemaLocation = "[http://maven.apache.org/POM/4.0.0](http://maven.apache.org/POM/4.0.0) [http://maven.apache.org/xsd/maven-4.0.0.xsd](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 = 1.8  repositories { mavenCentral()}dependencies { compile('org.springframework.boot:spring-boot-starter-web') testCompile('org.springframework.boot:spring-boot-starter-test')}

你能够应用上面的 Maven 或 Gradle 命令创立可执行的 JAR 文件，运行 Spring Boot 利用：

对于 Maven，应用以下命令：

mvn clean install

在 “BUILD SUCCESS” 之后，你能够在 target 目录下找到 JAR 文件：

对于 Gradle，应用以下命令：

gradle clean build

在 “BUILD SUCCESSFUL” 之后，你能够在 build/libs 目录下找到 JAR 文件：

能够应用以下命令运行 JAR 文件：

java –jar <JARFILE>

此刻，利用曾经在 Tomcat 8080 端口启动了，如下所示：

在 POSTMAN 利用中单击以下 URL，你能够看到上面的后果：

GET API: http://localhost:8080/products

在控制台窗口，你能够看到加在拦截器中的 System.out.println 打印进去的后果，截屏如下：