詳解使用Spring Boot開發Restful程序

一、簡介

Spring Boot是由Pivotal團隊提供的全新框架，其設計目的是用來簡化新spring應用的初始搭建以及開發過程。該框架使用了特定的方式來進行配置，從而使開發人員不再需要定義樣板化的配置。通過這種方式，Boot致力於在蓬勃發展的快速應用開發領域（rapid application development）成為領導者。

多年以來，Spring IO平台飽受非議的一點就是大量的XML配置以及復雜的依賴管理。在去年的SpringOne 2GX會議上，Pivotal的CTO Adrian Colyer回應了這些批評，並且特別提到該平台將來的目標之一就是實現免XML配置的開發體驗。Boot所實現的功能超出了這個任務的描述，開發人員不僅不再需要編寫XML，而且在一些場景中甚至不需要編寫繁瑣的import語句。在對外公開的beta版本剛剛發布之時，Boot描述了如何使用該框架在140個字符內實現可運行的web應用，從而獲得了極大的關注度，該樣例發表在tweet上。

Spring Boot不生成代碼，且完全不需要XML配置。其主要目標如下：

為所有的Spring開發工作提供一個更快、更廣泛的入門經驗。 開箱即用，你也可以通過修改默認值來快速滿足你的項目的需求。 提供了一系列大型項目中常見的非功能性特性，如嵌入式服務器、安全、指標，健康檢測、外部配置等。

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

二、開發環境准備

IDE：IntelliJ IDEA

官網地址：https://www.jetbrains.com/idea/download/

JDK：1.8

Maven

數據庫：MySQL

我將以一個用戶積分系統為例，開發一個Restful風格的服務端

三、第一個Restful程序

1.新建一個普通Maven工程

創建項目完成後目錄結構如下圖所示

2.在POM文件中加入對Spring-Boot的依賴

<?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.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.新建一個RestController來接收客戶端的請求，我們來模擬一個登錄請求

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;
 }}

關鍵字@RestController代表這個類是用Restful風格來訪問的，如果是普通的WEB頁面訪問跳轉時，我們通常會使用@Controller value = "/users/{username}" 代表訪問的URL是"http://host:PORT/users/實際的用戶名" method = RequestMethod.GET 代表這個HTTP請求必須是以GET方式訪問 consumes="application/json" 代表數據傳輸格式是json @PathVariable將某個動態參數放到URL請求路徑中 @RequestParam指定了請求參數名稱

4.新建啟動Restful服務端的啟動類

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.執行MappRunApplication的Main方法啟動Restful服務，可以看到控制台有如下輸出

 . ____   _   __ _ _
 /\\\\ / ___'_ __ _ _(_)_ __ __ _ \\ \\ \\ \\
( ( )\\___ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\
 \\\\/ ___)| |_)| | | | | || (_| | ) ) ) )
 ' |____| .__|_| |_|_| |_\\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: 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)

我們可以看到服務器是Tomcat，端口為8080

6.驗證

推薦大家使用Google的Postman插件來模擬請求

在發起請求前，請注意需要在Headers中設置Content-Type為application/json

到此一個基本的Restful風格的服務端就已經完成了，全部編碼時間不會超過5分鐘！

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持。