Spring Boot 简明教程

Spring Boot - Interceptor

你可以在 Spring Boot 中使用 Interceptor 在下列情况中执行操作 −

You can use the Interceptor in Spring Boot to perform operations under the following situations −

Before sending the request to the controller
Before sending the response to the client

例如，你可以在向控制器发送请求之前使用拦截器添加请求头，并在向客户端发送响应之前添加响应头。

For example, you can use an interceptor to add the request header before sending the request to the controller and add the response header before sending the response to the client.

要使用拦截器，你需要创建支持它的 @Component 类，并实现 HandlerInterceptor 接口。

To work with interceptor, you need to create @Component class that supports it and it should implement the HandlerInterceptor interface.

以下是使用拦截器时你需要了解的三种方法 −

The following are the three methods you should know about while working on Interceptors −

preHandle() method − This is used to perform operations before sending the request to the controller. This method should return true to return the response to the client.
postHandle() method − This is used to perform operations before sending the response to the client.
afterCompletion() method − This is used to perform operations after completing the request and response.

观察以下代码以更好地理解 −

Observe the following code for a better understanding −

@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 {}
}

你需要通过使用 WebMvcConfigurerAdapter 将此 Interceptor 注册到 InterceptorRegistry ，如下所示 −

You will have to register this Interceptor with InterceptorRegistry by using WebMvcConfigurerAdapter as shown below −

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

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

在下面的示例中，我们将触及 GET products API，其输出如下所示 −

In the example given below, we are going to hit the GET products API which gives the output as given under −

Interceptor 类 ProductServiceInterceptor.java 的代码如下 −

The code for the Interceptor class ProductServiceInterceptor.java is given below −

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");
   }
}

The code for Application Configuration class file to register the Interceptor into Interceptor Registry – ProductServiceInterceptorAppConfig.java is given below −

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);
   }
}

控制器类文件 ProductServiceController.java 的代码如下 −

The code for Controller class file ProductServiceController.java is given below −

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<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);
   }
}

Product.java 的 POJO 类文件的代码如下 −

The code for POJO class for Product.java is given below −

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;
   }
}

Spring Boot 应用程序类文件 DemoApplication.java 的代码如下 −

The code for main Spring Boot application class file DemoApplication.java is given below −

package com.tutorialspoint.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
}

Maven 构建代码 – pom.xml 如下所示 −

The code for Maven build – pom.xml is shown here −

<?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 构建代码 build.gradle 如下所示 −

The code for Gradle Build build.gradle is shown here −

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')
}

您可以创建一个可执行的 JAR 文件，并使用以下 Maven 或 Gradle 命令运行 Spring Boot 应用程序。

You can create an executable JAR file, and run the Spring Boot application by using the below Maven or Gradle commands.

对于 Maven，使用如下所示的命令：

For Maven, use the command as shown below −