Spring构建restfulWebService

Spring构建restfulWebService

这是官网提供的一个例子，这里练习。

实际上这里用的是Springboot来创建的。

What You Will Build

build a service that will accept HTTP GET requests at http://localhost:8080/greeting.

It will respond with a JSON representation of a greeting, as the following listing shows:

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

You can customize the greeting with an optional name parameter in the query string, as the following listing shows:

http://localhost:8080/greeting?name=User

The name parameter value overrides the default value of World and is reflected in the response, as the following listing shows:

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

练习

初始化一个springboot项目

使用springboot initializr来初始化一个springboot的web项目。

This example needs only the Spring Web dependency.

注意到项目的入口类为：

package com.example.restfulWebService2;

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

@SpringBootApplication
public class RestfulWebService2Application {

	public static void main(String[] args) {
		SpringApplication.run(RestfulWebService2Application.class, args);
	}

}

说明：

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

  • @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. For example, if spring-webmvc is on the classpath, this annotation 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 com/example package, letting it find the controllers.

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

SpringBoot设置允许断点和调试：

在ide (idea)资源目录resouces下有application.properties文件，可以添加一行:

debug=true

Create a Resource Representation Class

创建一个实体类

package com.example.restfulWebService2;

public class Greeting {
    public final long id;
    public 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;
    }
}

Create a Resource Controller

创建对应的controller来响应请求"/greeting"

package com.example.restfulWebService2;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.concurrent.atomic.AtomicLong;

@Controller
@ResponseBody
public class GreetingController {
    public static AtomicLong id = new AtomicLong();
    public static String template = "Hello, %s";

    @GetMapping(value = "/greeting")
    public Greeting greeting(@RequestParam(value = "name", defaultValue = "world") String name) {
        return new Greeting(id.incrementAndGet(), String.format(template, name));
    }
}

说明：

In Spring’s approach to building RESTful web services, HTTP requests are handled by a controller. These components are identified by the @RestController annotation, and the GreetingController shown in the listing (from src/main/java/com/example/restservice/GreetingController.java) handles GET requests for /greeting by returning a new instance of the Greeting class).

This application uses the Jackson JSON library to automatically marshal instances of type Greeting into JSON. Jackson is included by default by the web starter.

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

There are companion annotations for other HTTP verbs (e.g. @PostMapping for POST). There is also a @RequestMapping annotation that they all derive from, and can serve as a synonym (e.g. @RequestMapping(method=GET)).

@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.

This code uses Spring @RestController annotation, which marks the class as a controller where every method returns a domain object instead of a view. It is shorthand for including both @Controller and @ResponseBody.

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

测试

只有一个简单Java类和Controller，直接浏览器请求对应链接： http://localhost:8080/greeting?name=xxx就可以了。