我们注意到，在项目的 pom.xml 配置文件中，引入的依赖 spring-boot-starter-web 并没有指定其版本号
而在 maven 依赖中却可以发现其版本号为 2.3.4.RELEASE，这说明 SpringBoot 自动帮我们引入了对应版本的依赖，那么在哪儿可以找到 SpringBoot 自动引入的依赖信息呢？
- 在 pom.xml 配置文件中，按 ctrl 键同时鼠标点击 标签中 SpringBoot 依赖的 spring-boot-starter-parent(artifactId 标签)，即可进入 spring-boot-starter-parent-2.3.4.RELEASE.pom 配置文件，发现文件上面也有一个父项目
- 按 ctrl 键同时鼠标点击 spring-boot-dependencies，即可进入 spring-boot-dependencies-2.3.4.RELEASE.pom 配置文件，我们发现下面有一个 配置项，里面有如下配置信息
<properties>
<activemq.version>5.15.13</activemq.version>
<antlr2.version>2.7.7</antlr2.version>
<appengine-sdk.version>1.9.82</appengine-sdk.version>
<artemis.version>2.12.0</artemis.version>
<aspectj.version>1.9.6</aspectj.version>
<assertj.version>3.16.1</assertj.version>
<atomikos.version>4.0.6</atomikos.version>
<awaitility.version>4.0.3</awaitility.version>
<bitronix.version>2.1.4</bitronix.version>
<build-helper-maven-plugin.version>3.1.0</build-helper-maven-plugin.version>
<byte-buddy.version>1.10.14</byte-buddy.version>
<caffeine.version>2.8.5</caffeine.version>
<cassandra-driver.version>4.6.1</cassandra-driver.version>
<classmate.version>1.5.1</classmate.version>
<commons-codec.version>1.14</commons-codec.version>
<commons-dbcp2.version>2.7.0</commons-dbcp2.version>
<commons-lang3.version>3.10</commons-lang3.version>
<commons-pool.version>1.6</commons-pool.version>
<commons-pool2.version>2.8.1</commons-pool2.version>
<couchbase-client.version>3.0.8</couchbase-client.version>
<db2-jdbc.version>11.5.4.0</db2-jdbc.version>
<dependency-management-plugin.version>1.0.10.RELEASE</dependency-management-plugin.version>
<derby.version>10.14.2.0</derby.version>
<dropwizard-metrics.version>4.1.12.1</dropwizard-metrics.version>
<ehcache.version>2.10.6</ehcache.version>
<ehcache3.version>3.8.1</ehcache3.version>
<elasticsearch.version>7.6.2</elasticsearch.version>
<embedded-mongo.version>2.2.0</embedded-mongo.version>
<exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
<flatten-maven-plugin.version>1.2.5</flatten-maven-plugin.version>
<flyway.version>6.4.4</flyway.version>
<freemarker.version>2.3.30</freemarker.version>
<git-commit-id-plugin.version>3.0.1</git-commit-id-plugin.version>
<glassfish-el.version>3.0.3</glassfish-el.version>
<glassfish-jaxb.version>2.3.3</glassfish-jaxb.version>
<groovy.version>2.5.13</groovy.version>
<gson.version>2.8.6</gson.version>
<h2.version>1.4.200</h2.version>
<hamcrest.version>2.2</hamcrest.version>
<hazelcast.version>3.12.9</hazelcast.version>
<hazelcast-hibernate5.version>1.3.2</hazelcast-hibernate5.version>
<hibernate.version>5.4.21.Final</hibernate.version>
<hibernate-validator.version>6.1.5.Final</hibernate-validator.version>
<hikaricp.version>3.4.5</hikaricp.version>
<hsqldb.version>2.5.1</hsqldb.version>
<htmlunit.version>2.40.0</htmlunit.version>
<httpasyncclient.version>4.1.4</httpasyncclient.version>
<httpclient.version>4.5.12</httpclient.version>
<httpcore.version>4.4.13</httpcore.version>
<infinispan.version>10.1.8.Final</infinispan.version>
<influxdb-java.version>2.18</influxdb-java.version>
<jackson-bom.version>2.11.2</jackson-bom.version>
<jakarta-activation.version>1.2.2</jakarta-activation.version>
<jakarta-annotation.version>1.3.5</jakarta-annotation.version>
<jakarta-jms.version>2.0.3</jakarta-jms.version>
<jakarta-json.version>1.1.6</jakarta-json.version>
<jakarta-json-bind.version>1.0.2</jakarta-json-bind.version>
<jakarta-mail.version>1.6.5</jakarta-mail.version>
<jakarta-persistence.version>2.2.3</jakarta-persistence.version>
<jakarta-servlet.version>4.0.4</jakarta-servlet.version>
<jakarta-servlet-jsp-jstl.version>1.2.7</jakarta-servlet-jsp-jstl.version>
<jakarta-transaction.version>1.3.3</jakarta-transaction.version>
<jakarta-validation.version>2.0.2</jakarta-validation.version>
<jakarta-websocket.version>1.1.2</jakarta-websocket.version>
<jakarta-ws-rs.version>2.1.6</jakarta-ws-rs.version>
<jakarta-xml-bind.version>2.3.3</jakarta-xml-bind.version>
<jakarta-xml-soap.version>1.4.2</jakarta-xml-soap.version>
<jakarta-xml-ws.version>2.3.3</jakarta-xml-ws.version>
<janino.version>3.1.2</janino.version>
<javax-activation.version>1.2.0</javax-activation.version>
<javax-annotation.version>1.3.2</javax-annotation.version>
<javax-cache.version>1.1.1</javax-cache.version>
<javax-jaxb.version>2.3.1</javax-jaxb.version>
<javax-jaxws.version>2.3.1</javax-jaxws.version>
<javax-jms.version>2.0.1</javax-jms.version>
<javax-json.version>1.1.4</javax-json.version>
<javax-jsonb.version>1.0</javax-jsonb.version>
<javax-mail.version>1.6.2</javax-mail.version>
<javax-money.version>1.0.3</javax-money.version>
<javax-persistence.version>2.2</javax-persistence.version>
<javax-transaction.version>1.3</javax-transaction.version>
<javax-validation.version>2.0.1.Final</javax-validation.version>
<javax-websocket.version>1.1</javax-websocket.version>
<jaxen.version>1.2.0</jaxen.version>
<jaybird.version>3.0.9</jaybird.version>
<jboss-logging.version>3.4.1.Final</jboss-logging.version>
<jboss-transaction-spi.version>7.6.0.Final</jboss-transaction-spi.version>
<jdom2.version>2.0.6</jdom2.version>
<jedis.version>3.3.0</jedis.version>
<jersey.version>2.30.1</jersey.version>
<jetty-el.version>8.5.54</jetty-el.version>
<jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version>
<jetty-reactive-httpclient.version>1.1.4</jetty-reactive-httpclient.version>
<jetty.version>9.4.31.v20200723</jetty.version>
<jmustache.version>1.15</jmustache.version>
<johnzon.version>1.2.8</johnzon.version>
<jolokia.version>1.6.2</jolokia.version>
<jooq.version>3.13.4</jooq.version>
<json-path.version>2.4.0</json-path.version>
<json-smart.version>2.3</json-smart.version>
<jsonassert.version>1.5.0</jsonassert.version>
<jstl.version>1.2</jstl.version>
<jtds.version>1.3.1</jtds.version>
<junit.version>4.13</junit.version>
<junit-jupiter.version>5.6.2</junit-jupiter.version>
<kafka.version>2.5.1</kafka.version>
<kotlin.version>1.3.72</kotlin.version>
<kotlin-coroutines.version>1.3.8</kotlin-coroutines.version>
<lettuce.version>5.3.4.RELEASE</lettuce.version>
<liquibase.version>3.8.9</liquibase.version>
<log4j2.version>2.13.3</log4j2.version>
<logback.version>1.2.3</logback.version>
<lombok.version>1.18.12</lombok.version>
<mariadb.version>2.6.2</mariadb.version>
<maven-antrun-plugin.version>1.8</maven-antrun-plugin.version>
<maven-assembly-plugin.version>3.3.0</maven-assembly-plugin.version>
<maven-clean-plugin.version>3.1.0</maven-clean-plugin.version>
<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
<maven-dependency-plugin.version>3.1.2</maven-dependency-plugin.version>
<maven-deploy-plugin.version>2.8.2</maven-deploy-plugin.version>
<maven-enforcer-plugin.version>3.0.0-M3</maven-enforcer-plugin.version>
<maven-failsafe-plugin.version>2.22.2</maven-failsafe-plugin.version>
<maven-help-plugin.version>3.2.0</maven-help-plugin.version>
<maven-install-plugin.version>2.5.2</maven-install-plugin.version>
<maven-invoker-plugin.version>3.2.1</maven-invoker-plugin.version>
<maven-jar-plugin.version>3.2.0</maven-jar-plugin.version>
<maven-javadoc-plugin.version>3.2.0</maven-javadoc-plugin.version>
<maven-resources-plugin.version>3.1.0</maven-resources-plugin.version>
<maven-shade-plugin.version>3.2.4</maven-shade-plugin.version>
<maven-source-plugin.version>3.2.1</maven-source-plugin.version>
<maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
<maven-war-plugin.version>3.2.3</maven-war-plugin.version>
<micrometer.version>1.5.5</micrometer.version>
<mimepull.version>1.9.13</mimepull.version>
<mockito.version>3.3.3</mockito.version>
<mongodb.version>4.0.5</mongodb.version>
<mssql-jdbc.version>7.4.1.jre8</mssql-jdbc.version>
<mysql.version>8.0.21</mysql.version>
<nekohtml.version>1.9.22</nekohtml.version>
<neo4j-ogm.version>3.2.16</neo4j-ogm.version>
<netty.version>4.1.52.Final</netty.version>
<netty-tcnative.version>2.0.34.Final</netty-tcnative.version>
<nio-multipart-parser.version>1.1.0</nio-multipart-parser.version>
<oauth2-oidc-sdk.version>7.1.1</oauth2-oidc-sdk.version>
<nimbus-jose-jwt.version>8.19</nimbus-jose-jwt.version>
<ojdbc.version>19.3.0.0</ojdbc.version>
<okhttp3.version>3.14.9</okhttp3.version>
<oracle-database.version>19.3.0.0</oracle-database.version>
<pooled-jms.version>1.1.2</pooled-jms.version>
<postgresql.version>42.2.16</postgresql.version>
<prometheus-pushgateway.version>0.9.0</prometheus-pushgateway.version>
<quartz.version>2.3.2</quartz.version>
<querydsl.version>4.3.1</querydsl.version>
<r2dbc-bom.version>Arabba-SR7</r2dbc-bom.version>
<rabbit-amqp-client.version>5.9.0</rabbit-amqp-client.version>
<reactive-streams.version>1.0.3</reactive-streams.version>
<reactor-bom.version>Dysprosium-SR12</reactor-bom.version>
<rest-assured.version>3.3.0</rest-assured.version>
<rsocket.version>1.0.2</rsocket.version>
<rxjava.version>1.3.8</rxjava.version>
<rxjava-adapter.version>1.2.1</rxjava-adapter.version>
<rxjava2.version>2.2.19</rxjava2.version>
<saaj-impl.version>1.5.2</saaj-impl.version>
<selenium.version>3.141.59</selenium.version>
<selenium-htmlunit.version>2.40.0</selenium-htmlunit.version>
<sendgrid.version>4.4.8</sendgrid.version>
<servlet-api.version>4.0.1</servlet-api.version>
<slf4j.version>1.7.30</slf4j.version>
<snakeyaml.version>1.26</snakeyaml.version>
<solr.version>8.5.2</solr.version>
<spring-amqp.version>2.2.11.RELEASE</spring-amqp.version>
<spring-batch.version>4.2.4.RELEASE</spring-batch.version>
<spring-data-releasetrain.version>Neumann-SR4</spring-data-releasetrain.version>
<spring-framework.version>5.2.9.RELEASE</spring-framework.version>
<spring-hateoas.version>1.1.2.RELEASE</spring-hateoas.version>
<spring-integration.version>5.3.2.RELEASE</spring-integration.version>
<spring-kafka.version>2.5.6.RELEASE</spring-kafka.version>
<spring-ldap.version>2.3.3.RELEASE</spring-ldap.version>
<spring-restdocs.version>2.0.5.RELEASE</spring-restdocs.version>
<spring-retry.version>1.2.5.RELEASE</spring-retry.version>
<spring-security.version>5.3.4.RELEASE</spring-security.version>
<spring-session-bom.version>Dragonfruit-SR1</spring-session-bom.version>
<spring-ws.version>3.0.10.RELEASE</spring-ws.version>
<sqlite-jdbc.version>3.31.1</sqlite-jdbc.version>
<sun-mail.version>1.6.5</sun-mail.version>
<thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>
<thymeleaf-extras-data-attribute.version>2.0.1</thymeleaf-extras-data-attribute.version>
<thymeleaf-extras-java8time.version>3.0.4.RELEASE</thymeleaf-extras-java8time.version>
<thymeleaf-extras-springsecurity.version>3.0.4.RELEASE</thymeleaf-extras-springsecurity.version>
<thymeleaf-layout-dialect.version>2.4.1</thymeleaf-layout-dialect.version>
<tomcat.version>9.0.38</tomcat.version>
<unboundid-ldapsdk.version>4.0.14</unboundid-ldapsdk.version>
<undertow.version>2.1.4.Final</undertow.version>
<versions-maven-plugin.version>2.7</versions-maven-plugin.version>
<webjars-hal-browser.version>3325375</webjars-hal-browser.version>
<webjars-locator-core.version>0.45</webjars-locator-core.version>
<wsdl4j.version>1.6.3</wsdl4j.version>
<xml-maven-plugin.version>1.0.2</xml-maven-plugin.version>
<xmlunit2.version>2.7.0</xmlunit2.version>
</properties>
这里面已经声明了我们开发中可能会遇到的所有的依赖版本信息；这说明只要我们在开发 SpringBoot 项目的时候引入了父级依赖 spring-boot-starter-parent，其余对应的常用依赖的版本无需关心；这叫做 SpringBoot 版本依赖自动仲裁机制
-
如果我们要修改 SpringBoot 自动仲裁的依赖版本，例如：lombok 的版本，我们在 spring-boot-dependencies-2.3.4.RELEASE.pom 配置文件中可以看到其版本为：1.18.12
那么我们只需要在自己项目的 pom.xml 配置文件中，添加 配置项，覆盖 lombok.version 即可
然后在 pom.xml 配置文件中右键 Maven -> Reimport 刷新依赖即可；最终效果如下
注意：在 pom.xml 配置文件中 标签下添加的对应依赖版本的标签要和 spring-boot-dependencies-2.3.4.RELEASE.pom 中 配置下的版本的标签相同 -
未来在开发过程中，我们会使用到很多其他的 starter，官方的 starter 命名格式为：spring-boot-starter-xxx；只要引入 starter，对应这个 starter 关联的依赖都会自动引入；三方开发的 starter 命名格式为：xxx-spring-boot-starer；官方所有的 starter 在官网：https://docs.spring.io/spring-boot/docs/2.3.4.RELEASE/reference/html/using-spring-boot.html#using-boot-starter 下找到
-
所有场景启动器最底层的依赖是 spring-boot-starter 依赖，该依赖在 spring-boot-starter-web-2.3.4.RELEASE.pom 中
总结：引入的依赖默认可以不添加版本号，除非引入的是非版本仲裁的依赖才需要指定版本号
