构建一个RESTful Web服务

构建一个RESTful Web服务

构建一个RESTful Web服务

Building a RESTful Web Service

此教程将告诉你如何使用Spring创建一个”hello world”RESTful web服务

This guide walks you through the process of creating a “hello world” RESTful web service with Spring.


What you’ll build

你将构建一个接受HTTP GET请求的服务:

You’ll build a service that will accept HTTP GET requests at:



and respond with a JSON representation of a greeting:

{"id":1,"content":"Hello, World!"}


You can customize the greeting with an optional name parameter in the query string:



The name parameter value overrides the default value of “World” and is reflected in the response:

{"id":1,"content":"Hello, User!"}


What you’ll need


How to complete this guide


Like most Spring Getting Started guides, you can start from scratch and complete each step, or you can bypass basic setup steps that are already familiar to you. Either way, you end up with working code.


To start from scratch, move on to Build with Gradle.


To skip the basics, do the following:

  • 下载并解压此教程的源码仓库,或者使用Git进行clone:git clone https://github.com/spring-guides/gs-rest-service.git
  • cd into gs-rest-service/initial
  • 跳至创建一个资源表示类.


When you’re finished, you can check your results against the code in gs-rest-service/complete.


Create a resource representation class


Now that you’ve set up the project and build system, you can create your web service.


Begin the process by thinking about service interactions.

此服务将处理/greetingGET请求,请求字符串中有个name可选参数。GET请求将返回一个200 OK响应的,响应体是表示问候的一个字符串。看起来应该如下:

The service will handle GET requests for /greeting, optionally with a name parameter in the query string. The GET request should return a 200 OK response with JSON in the body that represents a greeting. It should look something like this:

    "id": 1,
    "content": "Hello, World!"


The id field is a unique identifier for the greeting, and content is the textual representation of the greeting.


To model the greeting representation, you create a resource representation class. Provide a plain old java object with fields, constructors, and accessors for the id and content data:


package hello;

public class Greeting {

    private final long id;
    private final String content;

    public Greeting(long id, String content) {
        this.id = id;
        this.content = content;

    public long getId() {
        return id;

    public String getContent() {
        return content;

在下面的步骤中,Spring将使用Jackson JSON库把Greeting类型实例自动转换为JSON。

As you see in steps below, Spring uses the Jackson JSON library to automatically marshal instances of type Greeting into JSON.


Next you create the resource controller that will serve these greetings.


Create a resource controller

使用Spring构建RESTful web服务,需要用一个控制器来处理HTTP请求。此组件可以使用@RestController注解来声明,下面的GreetingController处理/greetingGET请求,并返回一个Greeting类实例:

In Spring’s approach to building RESTful web services, HTTP requests are handled by a controller. These components are easily identified by the @RestController annotation, and the GreetingController below handles GET requests for /greeting by returning a new instance of the Greeting class:


package hello;

import java.util.concurrent.atomic.AtomicLong;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

public class GreetingController {

    private static final String template = "Hello, %s!";
    private final AtomicLong counter = new AtomicLong();

    public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {
        return new Greeting(counter.incrementAndGet(),
                            String.format(template, name));


This controller is concise and simple, but there’s plenty going on under the hood. Let’s break it down step by step.


The @RequestMapping annotation ensures that HTTP requests to /greeting are mapped to the greeting() method.

上面的例子并没有指定是GETPUT, POST等,因为@RequestMapping默认映射所有的HTTTP操作。使用@RequestMapping(method=GET)来限定其映射。

The above example does not specify GET vs. PUT, POST, and so forth, because @RequestMapping maps all HTTP operations by default. Use @RequestMapping(method=GET) to narrow this mapping.


@RequestParam binds the value of the query string parameter name into the name parameter of the greeting() method. If the name parameter is absent in the request, the defaultValue of “World” is used.


The implementation of the method body creates and returns a new Greeting object with id and content attributes based on the next value from the counter, and formats the given name by using the greeting template.

传统MVC控制器和RESTful web服务控制器的一个主要区别是HTTP响应体的创建方式。不同于依赖于视图技术使用服务端渲染将问候数据转为HTML,RESTful web服务控制器简单地填充并返回一个Greeting对象。对象数据将直接通过HTTP响应输出为JSON。

A key difference between a traditional MVC controller and the RESTful web service controller above is the way that the HTTP response body is created. Rather than relying on a view technology to perform server-side rendering of the greeting data to HTML, this RESTful web service controller simply populates and returns a Greeting object. The object data will be written directly to the HTTP response as JSON.

上面代码使用了Spring 4中新的注解@RestController,标记此类为控制类并且每个方法都返回对象而不是视图。相当于@Controller@ResponseBody的合并简化版。

This code uses Spring 4’s new @RestController annotation, which marks the class as a controller where every method returns a domain object instead of a view. It’s shorthand for @Controller and @ResponseBody rolled together.

Greeting对象必须转换为JSON。因为Spring的HTTP消息转换器的支持,你不需要手动转换。因为Jackson 2在classpath中,将自动选择Spring的MappingJackson2HttpMessageConverterGreeting实例转换为JSON。

The Greeting object must be converted to JSON. Thanks to Spring’s HTTP message converter support, you don’t need to do this conversion manually. Because Jackson 2 is on the classpath, Spring’s MappingJackson2HttpMessageConverter is automatically chosen to convert the Greeting instance to JSON.


Make the application executable

虽然可以将服务打包作为传统的WAR包,并部署在一个外部应用服务上,但下面展示的更简单的方法是创建一个独立的应用。你可以将所有东西打包为一个独立的可执行的JAR包,由Java main()方法驱动。这样一来,就代替了使用外部实例进行部署,转而使用Spring支持的内嵌Tomcat servlet容器作为HTTP运行时。

Although it is possible to package this service as a traditional WAR file for deployment to an external application server, the simpler approach demonstrated below creates a standalone application. You package everything in a single, executable JAR file, driven by a good old Java main() method. Along the way, you use Spring’s support for embedding the Tomcat servlet container as the HTTP runtime, instead of deploying to an external instance.


package hello;

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

public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);


@SpringBootApplication is a convenience annotation that adds all of the following:

  • @Configuration标记此类作为应用上下文的bean定义来源。
  • @EnableAutoConfiguration告诉Spring Boot基于classpath设置、其他bean或者各种属性设置来开始添加bean。
  • 通常你会在Spring MVC应用中添加@EnableWebMvc,如果在classpath中发现spring-webmvc,则Spring Boot会自动添加。此注解会标记应用为web应用,并激活一些关键行为例如设置一个DispatcherServlet
  • @ComponentScan告诉Spring在hello包中寻找其他组件、配置、服务等,也允许找到controllers。
  • @Configuration tags the class as a source of bean definitions for the application context.
  • @EnableAutoConfiguration tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
  • Normally you would add @EnableWebMvc for a Spring MVC app, but Spring Boot adds it automatically when it sees spring-webmvc on the classpath. This flags the application as a web application and activates key behaviors such as setting up a DispatcherServlet.
  • @ComponentScan tells Spring to look for other components, configurations, and services in the hello package, allowing it to find the controllers.

main()方法中使用了Spring Boot的SpringApplication.run()方法来加载一个应用。你注意到了没有任何XML吗?同样也没有web.xml文件。此web应用是100%纯Java并且你不要处理任何基础架构方面的配置。

The main() method uses Spring Boot’s SpringApplication.run() method to launch an application. Did you notice that there wasn’t a single line of XML? No web.xml file either. This web application is 100% pure Java and you didn’t have to deal with configuring any plumbing or infrastructure.


Build an executable JAR


You can run the application from the command line with Gradle or Maven. Or you can build a single executable JAR file that contains all the necessary dependencies, classes, and resources, and run that. This makes it easy to ship, version, and deploy the service as an application throughout the development lifecycle, across different environments, and so forth.

如果使用Gradle,可以使用./gradlew bootRun来运行应用。或者可以使用./gradlew build构建JAR文件。然后可以运行此JAR文件:

If you are using Gradle, you can run the application using ./gradlew bootRun. Or you can build the JAR file using ./gradlew build. Then you can run the JAR file:

java -jar build/libs/gs-rest-service-0.1.0.jar

如果使用Maven,可以使用./mvnw spring-boot:run来运行应用。或者可以使用./mvnw clean package构建JAR文件。然后可以运行此JAR文件:

If you are using Maven, you can run the application using ./mvnw spring-boot:run. Or you can build the JAR file with ./mvnw clean package. Then you can run the JAR file:

java -jar target/gs-rest-service-0.1.0.jar


The procedure above will create a runnable JAR. You can also opt to build a classic WAR file instead.


Logging output is displayed. The service should be up and running within a few seconds.


Test the service


Now that the service is up, visit http://localhost:8080/greeting, where you see:

{"id":1,"content":"Hello, World!"}

在请求字符串参数中提供一个name,如http://localhost:8080/greeting?name=User。注意content属性的值由”Hello, World!”变为了”Hello User!”:

Provide a name query string parameter with http://localhost:8080/greeting?name=User. Notice how the value of the content attribute changes from “Hello, World!” to “Hello User!”:

{"id":2,"content":"Hello, User!"}


This change demonstrates that the @RequestParam arrangement in GreetingController is working as expected. The name parameter has been given a default value of “World”, but can always be explicitly overridden through the query string.


Notice also how the id attribute has changed from 1 to 2. This proves that you are working against the same GreetingController instance across multiple requests, and that its counter field is being incremented on each call as expected.



恭喜!你已经完成了使用Spring来进行RESTful web服务的开发。

Congratulations! You’ve just developed a RESTful web service with Spring.