Spring Boot 快速入门(一)

简介 

相信很多人都接触spring框架很长时间了，每次搭建spring框架的时候都需要配置好多的jar、xml，做很多繁琐重复的配置，稍微不留神就会出现各种各样的问题，每次调试真的是香菇、蓝瘦啊。

spring boot的出现帮助我们彻底解决了这些jar的依赖，只需要很少的配置就可以完成我们的开发工作，我们可以把自己的应用打包成jar，使用java -jar来运行spring web应用，spring boot集成了很多的web容器，后面都会慢慢讲到这些，今天我们就开始使用spring boot完成一个最简单的web应用。

使用maven构建项目

spring官网提供了了一个非常方便的地址来帮助我们创建spring boot项目，http://start.spring.io/ ，输入相关参数点击 Generate Project 即可下载自动生成的压缩包。

该项目采用maven构建，加压后直接使用自己的IDE导入maven工程即可

1，打开pom文件就可以看到新的项目比传统的spring mvc项目的pom文件接口清晰了很多

　　

         <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
         <version>1.4.1.RELEASE</version>
     </parent>

第一个地方是多了上面的代码，这个spring boot会自动帮我门引入一些约定的配置，查看源码得知

 <?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>
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-dependencies</artifactId>
         <version>1.4.1.RELEASE</version>
         <relativePath>../../spring-boot-dependencies</relativePath>
     </parent>
     <artifactId>spring-boot-starter-parent</artifactId>
     <packaging>pom</packaging>
     <name>Spring Boot Starter Parent</name>
     <description>Parent pom providing dependency and plugin management for applications
         built with Maven</description>
     <url>http://projects.spring.io/spring-boot/</url>
     <organization>
         <name>Pivotal Software, Inc.</name>
         <url>http://www.spring.io</url>
     </organization>
     <properties>
         <java.version>1.6</java.version>
         <resource.delimiter>@</resource.delimiter> <!-- delimiter that doesn't clash with Spring ${} placeholders -->
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
     </properties>
     <dependencyManagement>
         <dependencies>
             <dependency>
                 <groupId>org.springframework</groupId>
                 <artifactId>spring-core</artifactId>
                 <version>${spring.version}</version>
                 <exclusions>
                     <exclusion>
                         <groupId>commons-logging</groupId>
                         <artifactId>commons-logging</artifactId>
                     </exclusion>
                 </exclusions>
             </dependency>
         </dependencies>
     </dependencyManagement>
     <build>
         <!-- Turn on filtering by default for application properties -->
         <resources>
             <resource>
                 <directory>${basedir}/src/main/resources</directory>
                 <filtering>true</filtering>
                 <includes>
                     <include>**/application*.yml</include>
                     <include>**/application*.properties</include>
                 </includes>
             </resource>
             <resource>
                 <directory>${basedir}/src/main/resources</directory>
                 <excludes>
                     <exclude>**/application*.yml</exclude>
                     <exclude>**/application*.properties</exclude>
                 </excludes>
             </resource>
         </resources>
         <pluginManagement>
             <plugins>
                 <!-- Apply more sensible defaults for user projects -->
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-failsafe-plugin</artifactId>
                     <executions>
                         <execution>
                             <goals>
                                 <goal>integration-test</goal>
                                 <goal>verify</goal>
                             </goals>
                         </execution>
                     </executions>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-jar-plugin</artifactId>
                     <configuration>
                         <archive>
                             <manifest>
                                 <mainClass>${start-class}</mainClass>
                                 <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                             </manifest>
                         </archive>
                     </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-surefire-plugin</artifactId>
                     <configuration>
                         <includes>
                             <include>**/*Tests.java</include>
                             <include>**/*Test.java</include>
                         </includes>
                         <excludes>
                             <exclude>**/Abstract*.java</exclude>
                         </excludes>
                     </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-war-plugin</artifactId>
                     <configuration>
                         <failOnMissingWebXml>false</failOnMissingWebXml>
                         <archive>
                             <manifest>
                                 <mainClass>${start-class}</mainClass>
                                 <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                             </manifest>
                         </archive>
                     </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.codehaus.mojo</groupId>
                     <artifactId>exec-maven-plugin</artifactId>
                     <configuration>
                         <mainClass>${start-class}</mainClass>
                     </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-resources-plugin</artifactId>
                     <version>2.6</version>
                     <configuration>
                         <delimiters>
                             <delimiter>${resource.delimiter}</delimiter>
                         </delimiters>
                         <useDefaultDelimiters>false</useDefaultDelimiters>
                     </configuration>
                 </plugin>
                 <plugin>
                     <groupId>pl.project13.maven</groupId>
                     <artifactId>git-commit-id-plugin</artifactId>
                     <version>2.1.11</version>
                     <executions>
                         <execution>
                             <goals>
                                 <goal>revision</goal>
                             </goals>
                         </execution>
                     </executions>
                     <configuration>
                         <verbose>true</verbose>
                         <dateFormat>yyyy-MM-dd'T'HH:mm:ssZ</dateFormat>
                         <generateGitPropertiesFile>true</generateGitPropertiesFile>
                         <generateGitPropertiesFilename>${project.build.outputDirectory}/git.properties</generateGitPropertiesFilename>
                     </configuration>
                 </plugin>
                 <!-- Support our own plugin -->
                 <plugin>
                     <groupId>org.springframework.boot</groupId>
                     <artifactId>spring-boot-maven-plugin</artifactId>
                     <executions>
                         <execution>
                             <goals>
                                 <goal>repackage</goal>
                             </goals>
                         </execution>
                     </executions>
                     <configuration>
                         <mainClass>${start-class}</mainClass>
                     </configuration>
                 </plugin>
                 <!-- Support shade packaging (if the user does not want to use our plugin) -->
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-shade-plugin</artifactId>
                     <dependencies>
                         <dependency>
                             <groupId>org.springframework.boot</groupId>
                             <artifactId>spring-boot-maven-plugin</artifactId>
                             <version>1.4.1.RELEASE</version>
                         </dependency>
                     </dependencies>
                     <configuration>
                         <keepDependenciesWithProvidedScope>true</keepDependenciesWithProvidedScope>
                         <createDependencyReducedPom>true</createDependencyReducedPom>
                         <filters>
                             <filter>
                                 <artifact>*:*</artifact>
                                 <excludes>
                                     <exclude>META-INF/*.SF</exclude>
                                     <exclude>META-INF/*.DSA</exclude>
                                     <exclude>META-INF/*.RSA</exclude>
                                 </excludes>
                             </filter>
                         </filters>
                     </configuration>
                     <executions>
                         <execution>
                             <phase>package</phase>
                             <goals>
                                 <goal>shade</goal>
                             </goals>
                             <configuration>
                                 <transformers>
                                     <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                         <resource>META-INF/spring.handlers</resource>
                                     </transformer>
                                     <transformer implementation="org.springframework.boot.maven.PropertiesMergingResourceTransformer">
                                         <resource>META-INF/spring.factories</resource>
                                     </transformer>
                                     <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                         <resource>META-INF/spring.schemas</resource>
                                     </transformer>
                                     <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                                     <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                         <mainClass>${start-class}</mainClass>
                                     </transformer>
                                 </transformers>
                             </configuration>
                         </execution>
                     </executions>
                 </plugin>
             </plugins>
         </pluginManagement>
     </build>
 </project>

spring boot默认帮我引入的jdk版本是1.6，如果需要改动，则在自己pom文件中直接重写<java.version>1.6</java.version>即可。

还可以看到它已经帮我们引入了spring-core和commons-logging包

继续往下看可以发现一些属性文件他也帮我定义好了规则，不需要我们自己在xml中定义了，已经一些maven插件的定义这里就不一一说明 ，具体插件是做什么用的，各位可以看下maven的相关知识。

第二个改变的地方是

   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter</artifactId>
 </dependency>
 
 <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-test</artifactId>
     <scope>test</scope>
 </dependency>
 
 <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-web</artifactId>
 </dependency>  

spring-boot-starter:核心模块，包括自动配置支持、日志

spring-boot-starter-test ：测试模块，包括JUnit、Hamcrest、Mockito

spring-boot-starter-web  ：开发web项目依赖
 
代码编写

说了这么多的配置，来让我们创建第一个class吧

@Controller
@EnableAutoConfiguration
@RequestMapping("/ctr")
public class SampleController
{
    @RequestMapping("/getStr")
    @ResponseBody
    String home(){
        return "Hello World";
    }
 
    @RequestMapping("/info")
    @ResponseBody
    public Map<String,String> getInfo(){
        Map<String, String> map = new HashMap<>();
        map.put("name", "jack");
        return map;
    }
 
    public static void main(String[] args)
    {
        SpringApplication.run(SampleController.class,args);
    }
}

到此为止，我们的第一个spring 的web项目就结束了，直接运行main方法，浏览器中输入：http://127.0.0.1:8080/ctr/info 可以看到运行结果  {"name": "jack"}

怎么样，是不是很神奇，没有启动任何的web容器，只需要执行main方法就可以运行我们的web项目了，而且配置就这么简单任性。