maven parent pom概述

maven parent pom 能够定义项目模型，包括构建方式、项目环境、项目依赖、输出JavaDoc、发布source源码等等。parent pom能使项目规范化，可以限定各种框架和类库的版本，便于后续的维护和升级。

SpringBoot parent pom

目前SpringBoot已成为Java项目基础框架，我们常用IDEA内的Spring Assistant插件创建SpringBoot项目。项目创建并加载完成后我们可以在项目的pom.xml中看到以下配置：

 <parent>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-parent</artifactId>
   <version>2.2.6.RELEASE</version>
 </parent>

这就是使用了SpringBoot parent pom，这个parent配置了spring-boot的编译和打包插件。我们能够看到spring-boot-starter-parent也有parent配置，为spring-boot-dependencies。

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>2.2.6.RELEASE</version>
    <relativePath>../../spring-boot-dependencies</relativePath>
  </parent>

spring-boot-dependenciespom有各种依赖以及依赖的版本信息的管理，这些版本都是经过SpringBoot官方测试过的，在自己项目中直接添加依赖即可，不需要设置版本号，如果项目中想要使用其他版本的依赖，配置版本号即可。

  <properties>
    <activemq.version>5.15.12</activemq.version>
    <antlr2.version>2.7.7</antlr2.version>
    <appengine-sdk.version>1.9.79</appengine-sdk.version>
    <artemis.version>2.10.1</artemis.version>
    <aspectj.version>1.9.5</aspectj.version>
    <assertj.version>3.13.2</assertj.version>
    <atomikos.version>4.0.6</atomikos.version>
    <awaitility.version>4.0.2</awaitility.version>
    <bitronix.version>2.1.4</bitronix.version>
    <build-helper-maven-plugin.version>3.0.0</build-helper-maven-plugin.version>
    <byte-buddy.version>1.10.8</byte-buddy.version>
    <caffeine.version>2.8.1</caffeine.version>
    <cassandra-driver.version>3.7.2</cassandra-driver.version>
    <classmate.version>1.5.1</classmate.version>
    <commons-codec.version>1.13</commons-codec.version>
    <commons-dbcp2.version>2.7.0</commons-dbcp2.version>
    <commons-lang3.version>3.9</commons-lang3.version>
    <commons-pool.version>1.6</commons-pool.version>
    <commons-pool2.version>2.7.0</commons-pool2.version>
    ...
  </properties>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-test</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-test-autoconfigure</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-actuator</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-actuator-autoconfigure</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-autoconfigure</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-autoconfigure-processor</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-metadata</artifactId>
        <version>2.2.6.RELEASE</version>
      </dependency>
      ...
    </dependencies>
  <dependencyManagement>

自定义parent pom

在公司项目中往往会使用相同的框架和工具类库包，如果每个项目使用的类库版本各不相同，后期协同速度将下降，因为每个人了解到的类库接口可能不一致。使用相同的类库版本能一定程度解决这个问题，而且团队之间能形成规范。如果类库版本需要集中更新，只需要更新parent pom中配置的版本即可，使用此parent pom的项目拉取新包后进行测试即可。

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <name>xx-springboot-v2-parent</name>
    <description>customized parent pom</description>
    <groupId>com.example</groupId>
    <artifactId>xx-springboot-v2-parent</artifactId>
    <version>1.0</version>
    <packaging>pom</packaging>

    <developers>
        <developer>
            <name>Moosion</name>
            <email>moosion@163.com</email>
        </developer>
    </developers>

    <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>

        <swagger.version>2.8.0</swagger.version>
        <gson.version>2.7</gson.version>
        <json-smart.version>2.2.1</json-smart.version>
        <spring-boot.version>2.2.6.RELEASE</spring-boot.version>
        <mysql-connector-java.version>5.1.44</mysql-connector-java.version>
        <mybatis-spring-boot-starter.version>2.0.0</mybatis-spring-boot-starter.version>

        <!-- 公司内部私有类库 -->
        <xx-bigtable.version>1.0.3</xx-bigtable.version>
        <xx-bigcache.version>2.0.5</xx-bigcache.version>
        <xx-bigstore.version>1.5.6</xx-bigstore.version>
        <xx-msgq.version>1.5.2</xx-msgq.version>
    </properties>

    <!-- 依赖管理 -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>com.example</groupId>
                <artifactId>xx-bigtable</artifactId>
                <version>${xx-bigtable.version}</version>
            </dependency>
            <dependency>
                <groupId>com.example</groupId>
                <artifactId>xx-bigstore</artifactId>
                <version>${xx-bigstore.version}</version>
            </dependency>
            <dependency>
                <groupId>com.example</groupId>
                <artifactId>xx-bigcache</artifactId>
                <version>${xx-bigcache.version}</version>
            </dependency>
            <dependency>
                <groupId>com.example</groupId>
                <artifactId>xx-msgq</artifactId>
                <version>${xx-msgq.version}</version>
            </dependency>
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger2</artifactId>
                <version>${swagger.version}</version>
            </dependency>
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger-ui</artifactId>
                <version>${swagger.version}</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>${mybatis-spring-boot-starter.version}</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>${mysql-connector-java.version}</version>
            </dependency>
            <dependency>
                <groupId>net.minidev</groupId>
                <artifactId>json-smart</artifactId>
                <version>${json-smart.version}</version>
            </dependency>
            <dependency>
                <groupId>com.google.code.gson</groupId>
                <artifactId>gson</artifactId>
                <version>${gson.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <!--  springboot所需编译和打包插件 -->
    <build>
        <resources>
            <resource>
                <filtering>true</filtering>
                <directory>${basedir}/src/main/resources</directory>
                <includes>
                    <include>**/application*.yml</include>
                    <include>**/application*.yaml</include>
                    <include>**/application*.properties</include>
                </includes>
            </resource>
            <resource>
                <directory>${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>${kotlin.version}</version>
                    <executions>
                        <execution>
                            <id>compile</id>
                            <phase>compile</phase>
                            <goals>
                                <goal>compile</goal>
                            </goals>
                        </execution>
                        <execution>
                            <id>test-compile</id>
                            <phase>test-compile</phase>
                            <goals>
                                <goal>test-compile</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
                        <jvmTarget>${java.version}</jvmTarget>
                        <javaParameters>true</javaParameters>
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <parameters>true</parameters>
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-failsafe-plugin</artifactId>
                    <executions>
                        <execution>
                            <goals>
                                <goal>integration-test</goal>
                                <goal>verify</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
                        <classesDirectory>${project.build.outputDirectory}</classesDirectory>
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <configuration>
                        <archive>
                            <manifest>
                                <mainClass>${start-class}</mainClass>
                                <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
                            </manifest>
                        </archive>
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-war-plugin</artifactId>
                    <configuration>
                        <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>
                    <artifactId>maven-resources-plugin</artifactId>
                    <configuration>
                        <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>${start-class}</mainClass>
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-shade-plugin</artifactId>
                    <executions>
                        <execution>
                            <phase>package</phase>
                            <goals>
                                <goal>shade</goal>
                            </goals>
                            <configuration>
                                <transformers>
                                    <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                        <resource>META-INF/spring.handlers</resource>
                                    </transformer>
                                    <transformer implementation="org.springframework.boot.maven.PropertiesMergingResourceTransformer">
                                        <resource>META-INF/spring.factories</resource>
                                    </transformer>
                                    <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                        <resource>META-INF/spring.schemas</resource>
                                    </transformer>
                                    <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                                    <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                        <mainClass>${start-class}</mainClass>
                                    </transformer>
                                </transformers>
                            </configuration>
                        </execution>
                    </executions>
                    <dependencies>
                        <dependency>
                            <groupId>org.springframework.boot</groupId>
                            <artifactId>spring-boot-maven-plugin</artifactId>
                            <version>2.2.6.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>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

properties和dependencyManagement根据自己公司项目需求配置，build可完全照抄spring-boot-starter-parentpom内定义的build，也可根据自己公司项目需求配置。

测试无误后发布到私有maven仓库，便于其他项目使用。

自定义parent pom的使用

创建新项目时，创建无模板maven项目，创建完成后在pom.xml中引入。同时需要添加springboot的maven插件spring-boot-maven-plugin，这样才能构建为和springboot相同的jar包。properties和dependencies根据项目需求配置。

<parent>
    <groupId>com.example</groupId>
    <artifactId>xx-springboot-v2-parent</artifactId>
    <version>1.0</version>
    <relativePath/>
</parent>

<properties>
    <java.version>1.8</java.version>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <resource.delimiter>@</resource.delimiter>
    <maven.compiler.source>${java.version}</maven.compiler.source>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.target>${java.version}</maven.compiler.target>
    ...
</properties>

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

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
        <optional>true</optional>
    </dependency>
    ...
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <version>${spring-boot.version}</version>
        </plugin>
    </plugins>
</build>