先说spring-boot-dependencies的作用，就是统一管理spring-boot-starter的各个版本控制。在pom.xml再引入starter就无须引入版本号。

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>1.5.4.RELEASE</version>
</parent>

在pom.xml中的添加。

先上一下spring-boot-starter-parent源码

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>2.5.4</version>
  </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>
  <properties>
    <java.version>1.8</java.version>
    <resource.delimiter>@</resource.delimiter>
    <maven.compiler.source>${java.version}</maven.compiler.source>
    <maven.compiler.target>${java.version}</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  </properties>
  <url>https://spring.io/projects/spring-boot</url>
  <licenses>
    <license>
      <name>Apache License, Version 2.0</name>
      <url>https://www.apache.org/licenses/LICENSE-2.0</url>
    </license>
  </licenses>
  <developers>
    <developer>
      <name>Pivotal</name>
      <email>info@pivotal.io</email>
      <organization>Pivotal Software, Inc.</organization>
      <organizationUrl>https://www.spring.io</organizationUrl>
    </developer>
  </developers>
  <scm>
    <url>https://github.com/spring-projects/spring-boot</url>
  </scm>
  <build>
    <resources>
      <resource>
        <directory>${basedir}/src/main/resources</directory>
        <filtering>true</filtering>
        <includes>
          <include>**/application*.yml</include>
          <include>**/application*.yaml</include>
          <include>**/application*.properties</include>
        </includes>
      </resource>
      <resource>
        <directory>${basedir}/src/main/resources</directory>
        <excludes>
          <exclude>**/application*.yml</exclude>
          <exclude>**/application*.yaml</exclude>
          <exclude>**/application*.properties</exclude>
        </excludes>
      </resource>
    </resources>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.jetbrains.kotlin</groupId>
          <artifactId>kotlin-maven-plugin</artifactId>
          <version>${kotlin.version}</version>
          <configuration>
            <jvmTarget>${java.version}</jvmTarget>
            <javaParameters>true</javaParameters>
          </configuration>
          <executions>
            <execution>
              <id>compile</id>
              <phase>compile</phase>
              <goals>
                <goal>compile</goal>
              </goals>
            </execution>
            <execution>
              <id>test-compile</id>
              <phase>test-compile</phase>
              <goals>
                <goal>test-compile</goal>
              </goals>
            </execution>
          </executions>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <configuration>
            <parameters>true</parameters>
          </configuration>
        </plugin>
        <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>
          <configuration>
            <classesDirectory>${project.build.outputDirectory}</classesDirectory>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-jar-plugin</artifactId>
          <configuration>
            <archive>
              <manifest>
                <mainClass>${start-class}</mainClass>
                <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
              </manifest>
            </archive>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-war-plugin</artifactId>
          <configuration>
            <archive>
              <manifest>
                <mainClass>${start-class}</mainClass>
                <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
              </manifest>
            </archive>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-resources-plugin</artifactId>
          <configuration>
            <propertiesEncoding>${project.build.sourceEncoding}</propertiesEncoding>
            <delimiters>
              <delimiter>${resource.delimiter}</delimiter>
            </delimiters>
            <useDefaultDelimiters>false</useDefaultDelimiters>
          </configuration>
        </plugin>
        <plugin>
          <groupId>pl.project13.maven</groupId>
          <artifactId>git-commit-id-plugin</artifactId>
          <executions>
            <execution>
              <goals>
                <goal>revision</goal>
              </goals>
            </execution>
          </executions>
          <configuration>
            <verbose>true</verbose>
            <dateFormat>yyyy-MM-dd'T'HH:mm:ssZ</dateFormat>
            <generateGitPropertiesFile>true</generateGitPropertiesFile>
            <generateGitPropertiesFilename>${project.build.outputDirectory}/git.properties</generateGitPropertiesFilename>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-maven-plugin</artifactId>
          <executions>
            <execution>
              <id>repackage</id>
              <goals>
                <goal>repackage</goal>
              </goals>
            </execution>
          </executions>
          <configuration>
            <mainClass>${start-class}</mainClass>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-shade-plugin</artifactId>
          <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>
          <dependencies>
            <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-maven-plugin</artifactId>
              <version>2.5.4</version>
            </dependency>
          </dependencies>
          <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>

可以看出

1.spring-boot-starter-parent的parent是spring-boot-dependencies
2.parent 的基本功能有哪些？如下

定义了 Java 编译版本，如上为 1.8。
使用 UTF-8 格式编码
maven源文件和目标文件编译的版本
执行打包操作的配置
自动化的资源过滤
自动化的插件配置
针对 application.properties 和 application.yml 的资源过滤，包括通过 profile 定义的不同环境的配置文件，例如 application-dev.properties 和 application-dev.yml