Spring Boot - 快速构建一个基本的Restful程序

##一、简介
最近团队中Android和IOS的童鞋向我提出来一个要求，想学习一下服务端是如何开发的。我们的后端主要是用Spring MVC来实现Restful风格的接口，业务层和数据层使用Spring Framework+Mybatis来实现。但是这些东西一来配置文件太多，原理也很难快速掌握，对于前端童鞋来说，门槛较高，有没有更便捷的框架供大家学习呢？经过几天的时间研究，终于找到了Spring Boot这个大杀器。

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。

Spring Boot不生成代码，且完全不需要XML配置。其主要目标如下：

为所有的Spring开发工作提供一个更快、更广泛的入门经验。

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。

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。

Spring Boot官网: http://projects.spring.io/spring-boot/

##二、开发环境准备

IDE：IntelliJ IDEA

官网地址：https://www.jetbrains.com/idea/download/

JDK：1.8

Maven

数据库：MySQL

我花5分钟开发一个RESTful服务端程序

##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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>

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

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.3.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;
}}

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

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

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

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

@PathVariable将某个动态参数放到URL请求路径中

@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！

完整代码戳这里: Chapter 1 - 5分钟构建一个基本的Restful程序