分享利用Spring Boot开发Restful程序的实例教程

一、简介

Spring Boot是由Pivotal团队提供的全新框架，其设计目的是用来简化新spring应用的初始搭建以及开发过程。该框架使用了特定的方式来进行配置，从而使开发人员不再需要定义样板化的配置。通过这种方式，Boot致力于在蓬勃发展的快速应用开发领域（rapid application development）成为领导者。

多年以来，Spring IO平台饱受非议的一点就是大量的XML配置以及复杂的依赖管理。在去年的SpringOne 2GX会议上，Pivotal的CTO Adrian Colyer回应了这些批评，并且特别提到该平台将来的目标之一就是实现免XML配置的开发体验。Boot所实现的功能超出了这个任务的描述，开发人员不仅不再需要编写XML，而且在一些场景中甚至不需要编写繁琐的import语句。在对外公开的beta版本刚刚发布之时，Boot描述了如何使用该框架在140个字符内实现可运行的web应用，从而获得了极大的关注度，该样例发表在tweet上。

Spring Boot不生成代码，且完全不需要XML配置。其主要目标如下：

1. 为所有的Spring开发工作提供一个更快、更广泛的入门经验。

2. 开箱即用，你也可以通过修改默认值来快速满足你的项目的需求。

3. 提供了一系列大型项目中常见的非功能性特性，如嵌入式服务器、安全、指标，健康检测、外部配置等。

二、开发环境准备

IDE：IntelliJ IDEA

JDK：1.8

Maven

数据库：MySQL

我将以一个用户积分系统为例，开发一个Restful风格的服务端

三、第一个Restful程序

1.新建一个普通Maven工程

创建项目完成后目录结构如下图所示

2.在POM文件中加入对Spring-Boot的依赖

<?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 maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>

 <groupId>com.bluecoffee</groupId>
 <artifactId>mapp</artifactId>
 <version>1.0-SNAPSHOT</version>

 <parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>1.4.1.RELEASE</version>
  <relativePath /> <!-- lookup parent from repository -->
 </parent>

 <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <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>

3.新建一个RestController来接收客户端的请求，我们来模拟一个登录请求

package com.yepit.mapp.rest;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.bind.annotation.*;

/**
 * Created by qianlong on 16/7/20.
 */
@RestController
public class UserController {

 @RequestMapping(value = "/users/{username}",method = RequestMethod.GET,consumes="application/json")
 public String getUser(@PathVariable String username, @RequestParam String pwd){
  return "Welcome,"+username;
 }}

1. 关键字@RestController代表这个类是用Restful风格来访问的，如果是普通的WEB页面访问跳转时，我们通常会使用@Controller

2. value = "/users/{username}" 代表访问的URL是"http://host:PORT/users/实际的用户名"

3. method = RequestMethod.GET 代表这个HTTP请求必须是以GET方式访问

4. consumes="application/json" 代表数据传输格式是json

5. @PathVariable将某个动态参数放到URL请求路径中

6. @RequestParam指定了请求参数名称
   

4.新建启动Restful服务端的启动类

package com.yepit.mapp;

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

/**
 * Created by qianlong on 16/7/20.
 */
@SpringBootApplication
public class MappRunApplication {

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

5.执行MappRunApplication的Main方法启动Restful服务，可以看到控制台有如下输出

 .    _    _ _
 /\\\\ / _'_  _ _(_)_   _ \\ \\ \\ \\
( ( )\\_ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\
 \\\\/ _)| |_)| | | | | || (_| | ) ) ) )
 ' || .|_| |_|_| |_\\, | / / / /
 =========|_|==============|_/=/_/_/_/
 :: Spring Boot ::  (v1.3.3.RELEASE)

2016-07-20 16:49:43.334 INFO 2106 --- [   main] com.yepit.mapp.MappRunApplication  : Starting MappRunApplication on bogon with PID 2106 (/Users/qianlong/workspace/spring-boot-samples/target/classes started by qianlong in /Users/qianlong/workspace/spring-boot-samples)
2016-07-20 16:49:43.338 INFO 2106 --- [   main] com.yepit.mapp.MappRunApplication  : No active profile set, falling back to default profiles: default
2016-07-20 16:49:43.557 INFO 2106 --- [   main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@543e710e: startup date [Wed Jul 20 16:49:43 CST 2016]; root of context hierarchy
2016-07-20 16:49:44.127 INFO 2106 --- [   main] o.s.b.f.s.DefaultListableBeanFactory  : Overriding bean definition for bean 'beanNameViewResolver' with a different definition: replacing [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration.class]] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter; factoryMethodName=beanNameViewResolver; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/boot/autoconfigure/web/WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter.class]]
2016-07-20 16:49:44.658 INFO 2106 --- [   main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2016-07-20 16:49:44.672 INFO 2106 --- [   main] o.apache.catalina.core.StandardService : Starting service Tomcat
2016-07-20 16:49:44.673 INFO 2106 --- [   main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.0.32
2016-07-20 16:49:44.759 INFO 2106 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]  : Initializing Spring embedded WebApplicationContext
2016-07-20 16:49:44.759 INFO 2106 --- [ost-startStop-1] o.s.web.context.ContextLoader   : Root WebApplicationContext: initialization completed in 1207 ms
2016-07-20 16:49:44.972 INFO 2106 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2016-07-20 16:49:44.977 INFO 2106 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2016-07-20 16:49:44.978 INFO 2106 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2016-07-20 16:49:44.978 INFO 2106 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2016-07-20 16:49:44.978 INFO 2106 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2016-07-20 16:49:45.184 INFO 2106 --- [   main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@543e710e: startup date [Wed Jul 20 16:49:43 CST 2016]; root of context hierarchy
2016-07-20 16:49:45.251 INFO 2106 --- [   main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/users],methods=[GET],consumes=[application/json]}" onto public java.lang.String com.yepit.mapp.rest.UserController.getUser(java.lang.String,java.lang.String)
2016-07-20 16:49:45.253 INFO 2106 --- [   main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2016-07-20 16:49:45.254 INFO 2106 --- [   main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2016-07-20 16:49:45.275 INFO 2106 --- [   main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2016-07-20 16:49:45.275 INFO 2106 --- [   main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2016-07-20 16:49:45.306 INFO 2106 --- [   main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2016-07-20 16:49:45.380 INFO 2106 --- [   main] o.s.j.e.a.AnnotationMBeanExporter  : Registering beans for JMX exposure on startup
2016-07-20 16:49:45.462 INFO 2106 --- [   main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2016-07-20 16:49:45.467 INFO 2106 --- [   main] com.yepit.mapp.MappRunApplication  : Started MappRunApplication in 2.573 seconds (JVM running for 3.187)

我们可以看到服务器是Tomcat，端口为8080

6.验证

推荐大家使用Google的Postman插件来模拟请求

在发起请求前，请注意需要在Headers中设置Content-Type为application/json

到此一个基本的Restful风格的服务端就已经完成了，全部编码时间不会超过5分钟！

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