前言
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。
问题：使用spring boot有什么好处？
其实就是简单、快速、方便！平时如果我们需要搭建一个spring web项目的时候需要怎么做呢？
1）配置web.xml，加载spring和spring mvc
2）配置数据库连接、配置spring事务
3）配置加载配置文件的读取，开启注解
4）配置日志文件
...
配置完成之后部署tomcat 调试
...
现在非常流行微服务，如果我这个项目仅仅只是需要发送一个邮件，如果我的项目仅仅是生产一个积分；我都需要这样折腾一遍!
但是如果使用spring boot呢？
很简单，我仅仅只需要非常少的几个配置就可以迅速方便的搭建起来一套web项目或者是构建一个微服务！
Spring Boot 应用搭建
1、创建一个新项目（Create New Project）
选择Spring Initializr,Project SDK 选择1.8，Service URL选择默认，点击Next，如图所示：
2、项目配置，点击Next，如图所示：
解释：
Group：对应pom文件中的groupId，项目组织的唯一标识，对应Java包的结构
Artifact：对应pom文件的artifactId，项目唯一标识，对应项目名称
Type：我们是Maven构建的，那么选择第一个Maven Project
Language：开发语言，选择Java
Packaging：打包类型，打包成Jar文件
Java Version：jdk版本，选择1.8
Version：项目版本，对应pom文件的version
Name：项目名称
Description：项目描述，对应pom文件的description
Package：包名
3、Spring Boot 版本选择，我这里选择了2.0.5，勾选Web下的web，点击Next，如图所示：
4、填写项目名称，项目存放的目录，点击 Finish
5、根据个人习惯，可以将一下三个无关文件删除，干净目录，如图所示：
6、清理后的项目目录，如图所示：
到此为止，一个Spring boot 应用在Intellij IDEA上搭建完成。
其中创建项目时填写的属性在pom文件中可以看到，项目生成的pom.xml如下：
<?xml version="1.0" encoding="UTF-8"?><project xmlns="/POM/4.0.0" xmlns:xsi="/2001/XMLSchema-instance"xsi:schemaLocation="/POM/4.0.0 /xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.demo</groupId><artifactId>springboot</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>springboot</name><description>Demo project for Spring Boot</description><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.5.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><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>
7、创建一个Controller进行测试
package com.demo.springboot.controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;/*** TestController** @author WuYuxiang* @date /9/20*/@RestController@RequestMapping("/")public class TestController {@RequestMapping("springboot")public String testSpringBoot() {return "Hello Spring Boot ! ";}}
@RestController注解，相当于@Controller+@ResponseBody两个注解的结合，返回json数据不需要在方法前面加@ResponseBody注解了，但使用@RestController这个注解，就不能返回jsp,html页面，视图解析器无法解析jsp,html页面，如果需要返回jsp，html页面，则使用@Controller注解。
整个项目的启动类就是上面的SpringbootApplication
package com.demo.springboot;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class SpringbootApplication {public static void main(String[] args) {SpringApplication.run(SpringbootApplication.class, args);}}
8、启动项目，如图所示：
9、启动成功信息，端口8080
信息：Tomcat started on port(s): 8080 (http) with context path ''
E:\DevelopEnv\JDK\jdk-1.8\jdk1.8.0_181\bin\java.exe -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:62736,suspend=y,server=n -XX:TieredStopAtLevel=1 -noverify -Dspring.output.ansi.enabled=always -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=62733 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djava.rmi.server.hostname=localhost -Dspring.liveBeansView.mbeanDomain -Dspring.application.admin.enabled=true -javaagent:C:\Users\Administrator\.IntelliJIdea.2\system\captureAgent\debugger-agent.jar=file:/C:/Users/Administrator/AppData/Local/Temp/capture4324.props -Dfile.encoding=UTF-8 -classpath 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\slf4j\slf4j-api\1.7.25\slf4j-api-1.7.25.jar;E:\Maven\MavenRepository\org\springframework\spring-core\5.0.9.RELEASE\spring-core-5.0.9.RELEASE.jar;E:\Maven\MavenRepository\org\springframework\spring-jcl\5.0.9.RELEASE\spring-jcl-5.0.9.RELEASE.jar;C:\Develop\IntellijIdea\Idea.2.2\InstallFiles\IntelliJ IDEA .2.2\lib\idea_rt.jar" com.demo.springboot.SpringbootApplicationConnected to the target VM, address: '127.0.0.1:62736', transport: 'socket'. _____ __ _ _/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/ ___)| |_)| | | | | || (_| | ) ) ) )' |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot :: (v2.0.5.RELEASE)-09-20 10:43:25.299 INFO 8884 --- [ main] c.demo.springboot.SpringbootApplication : Starting SpringbootApplication on VikasDhanve with PID 8884 (D:\DevProject\java\demo\springboot\target\classes started by Administrator in D:\DevProject\java\demo\springboot)-09-20 10:43:25.299 INFO 8884 --- [ main] c.demo.springboot.SpringbootApplication : No active profile set, falling back to default profiles: default-09-20 10:43:25.330 INFO 8884 --- [ main] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@1672fe87: startup date [Thu Sep 20 10:43:25 CST ]; root of context hierarchy-09-20 10:43:25.908 INFO 8884 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)-09-20 10:43:25.924 INFO 8884 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]-09-20 10:43:25.924 INFO 8884 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.34-09-20 10:43:25.924 INFO 8884 --- [ost-startStop-1] o.a.catalina.core.AprLifecycleListener : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: [E:\DevelopEnv\JDK\jdk-1.8\jdk1.8.0_181\bin;C:\windows\Sun\Java\bin;C:\windows\system32;C:\windows;C:\Program Files (x86)\Common Files\Oracle\Java\javapath;E:\DevelopEnv\Python\Python37\Scripts\;E:\DevelopEnv\Python\Python37\;C:\Program Files (x86)\Common Files\Intel\Shared Libraries\redist\intel64\compiler;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;E:\DevelopEnv\JDK\jdk-1.8\jdk1.8.0_181\bin;E:\DevelopEnv\JDK\jdk-1.8\jdk1.8.0_181\jre\bin;C:\Program Files\dotnet\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;E:\VersionTools\Git\InstallFiles\Git\cmd;E:\Maven\apache-maven-3.5.4\bin;C:\Program Files (x86)\Microsoft SQL Server\140\Tools\Binn\;C:\Program Files\Microsoft SQL Server\140\Tools\Binn\;C:\Program Files (x86)\Microsoft SQL Server\140\DTS\Binn\;C:\Program Files\Microsoft SQL Server\140\DTS\Binn\;C:\Program Files\Microsoft SQL Server\Client SDK\ODBC\130\Tools\Binn\;C:\Program Files (x86)\Microsoft SQL Server\Client SDK\ODBC\130\Tools\Binn\;C:\Program Files (x86)\Microsoft SQL Server\140\Tools\Binn\ManagementStudio\;C:\Users\Administrator\AppData\Local\Microsoft\WindowsApps;;.]-09-20 10:43:25.971 INFO 8884 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext-09-20 10:43:25.987 INFO 8884 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 672 ms-09-20 10:43:26.018 INFO 8884 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Servlet dispatcherServlet mapped to [/]-09-20 10:43:26.018 INFO 8884 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]-09-20 10:43:26.018 INFO 8884 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]-09-20 10:43:26.018 INFO 8884 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]-09-20 10:43:26.018 INFO 8884 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]-09-20 10:43:26.096 INFO 8884 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]-09-20 10:43:26.237 INFO 8884 --- [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@1672fe87: startup date [Thu Sep 20 10:43:25 CST ]; root of context hierarchy-09-20 10:43:26.284 INFO 8884 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/springboot]}" onto public java.lang.String com.demo.springboot.controller.TestController.testSpringBoot()-09-20 10:43:26.284 INFO 8884 --- [ 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.servlet.error.BasicErrorController.error(javax.servlet.http.HttpServletRequest)-09-20 10:43:26.284 INFO 8884 --- [ 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.servlet.error.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)-09-20 10:43:26.299 INFO 8884 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]-09-20 10:43:26.299 INFO 8884 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]-09-20 10:43:26.393 INFO 8884 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup-09-20 10:43:26.424 INFO 8884 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''-09-20 10:43:26.424 INFO 8884 --- [ main] c.demo.springboot.SpringbootApplication : Started SpringbootApplication in 1.375 seconds (JVM running for 2.532)-09-20 10:43:41.334 INFO 8884 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring FrameworkServlet 'dispatcherServlet'-09-20 10:43:41.334 INFO 8884 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization started-09-20 10:43:41.350 INFO 8884 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization completed in 16 ms
10、浏览器输入URL：http://localhost:8080/springboot
效果如图所示：
