springboot的pom文件：
- 附上springboot的完成pom文件
<?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.ljj</groupId>
<artifactId>Ljjboot-01</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Ljjboot-01</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.0.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</artifactId>
</dependency>
<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>
- 可以看到他的父类项目为spring-boot-starter-parent
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.0.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
我们点击进去可以看到：
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.1.0.RELEASE</version>
<relativePath>../../spring-boot-dependencies</relativePath>
</parent>
<artifactId>spring-boot-starter-parent</artifactId>
spring-boot-starter-parent的父类为：spring-boot-dependencies
点击进去：
<properties>
<activemq.version>5.15.7</activemq.version>
<antlr2.version>2.7.7</antlr2.version>
<appengine-sdk.version>1.9.67</appengine-sdk.version>
<artemis.version>2.6.3</artemis.version>
<aspectj.version>1.9.2</aspectj.version>
<assertj.version>3.11.1</assertj.version>
<atomikos.version>4.0.6</atomikos.version>
<bitronix.version>2.1.4</bitronix.version>
<build-helper-maven-plugin.version>3.0.0</build-helper-maven-plugin.version>
<byte-buddy.version>1.9.3</byte-buddy.version>
<caffeine.version>2.6.2</caffeine.version>
<cassandra-driver.version>3.6.0</cassandra-driver.version>
<classmate.version>1.4.0</classmate.version>
<commons-codec.version>1.11</commons-codec.version>
<commons-dbcp2.version>2.5.0</commons-dbcp2.version>
<commons-lang3.version>3.8.1</commons-lang3.version>
<commons-pool.version>1.6</commons-pool.version>
<commons-pool2.version>2.6.0</commons-pool2.version>
<couchbase-cache-client.version>2.1.0</couchbase-cache-client.version>
<couchbase-client.version>2.7.0</couchbase-client.version>
<derby.version>10.14.2.0</derby.version>
<dom4j.version>1.6.1</dom4j.version>
<dropwizard-metrics.version>4.0.3</dropwizard-metrics.version>
<ehcache.version>2.10.6</ehcache.version>
<ehcache3.version>3.6.1</ehcache3.version>
<elasticsearch.version>6.4.2</elasticsearch.version>
<embedded-mongo.version>2.1.1</embedded-mongo.version>
<exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
<flatten-maven-plugin.version>1.0.1</flatten-maven-plugin.version>
<flyway.version>5.2.1</flyway.version>
<freemarker.version>2.3.28</freemarker.version>
<hamcrest.version>1.3</hamcrest.version>
<hazelcast.version>3.11</hazelcast.version>
<hazelcast-hibernate5.version>1.2.3</hazelcast-hibernate5.version>
<hibernate.version>5.3.7.Final</hibernate.version>
....
</properties>
这个spring-boot-denpendencies来真正管理Spring Boot应用里面的所有依赖版本；
所以我们可以知道：
Spring Boot的版本仲裁中心；
以后我们导入依赖默认是不需要写版本；（没有在dependencies里面管理的依赖自然需要声明版本号）
springboot场景启动器
- 我们通过spring-boot-starts-web启动器为例：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring‐boot‐starter‐web</artifactId>
</dependency>
我们点击进去:
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<version>2.1.0.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-json</artifactId>
<version>2.1.0.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<version>2.1.0.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator</artifactId>
<version>6.0.13.Final</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.1.2.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.1.2.RELEASE</version>
<scope>compile</scope>
</dependency>
</dependencies>
可以看出：spring-boot-starter-web：
spring-boot-starter：spring-boot场景启动器；帮我们导入了web模块正常运行所依赖的组件；
所以我们可以这么理解：
Spring Boot将所有的功能场景都抽取出来，做成一个个的starters（启动器），只需要在项目里面引入这些starter 相关场景的所有依赖都会导入进来。要用什么功能就导入什么场景的启动器
