Maven系列第7篇：聚合、继承、单继承问题详解，必备技能！

2019 年 11 月 25 日
笔记

maven系列目标：从入门开始开始掌握一个高级开发所需要的maven技能。

这是maven系列第7篇。

整个maven系列的内容前后是有依赖的，如果之前没有接触过maven，建议从第一篇看起，本文尾部有maven完整系列的连接。

本篇内容

maven中聚合详解
maven中继承详解
pom.xml中parent元素的使用详解
pom.xml中dependencyManagement元素使用详解
pom.xml中pluginManagement元素使用详解
单继承存在的问题及解决方案详解（springboot,springcloud中会常用）
解答上一篇遗留的2个问题

聚合

原始需求

我们需要使用java做一个电商网站，涉及到：pc端网站、h5微站、移动端接口部分，那么我们可以使用maven创建3个项目用于这3块业务的开发，3个项目名称如下：

javacode2018-pc  javacode2018-h5  javacode2018-api

这3个项目的groupId都是com.javacode2018，artifactId取上面的，我们使用maven来搭建项目结构。

实现

创建第一个javacode2018-pc项目

打开idea，点击File->New->Project，选择Maven，如下：

点击Next，输入项目坐标信息，如下：

点击Next，输入Project name 为javacode2018-pc，如下：

点击Finish，创建成功，如下：

配置一下idea的maven环境，点击File->Settings，如下图：

点击上面的OK完成配置。

大家再按照上面一样的操作，分别创建另外2个项目javacode2018-h5和javacode2018-api，创建完成之后，另外2个项目如下图：

上面3个项目由整个项目组6个人共同开发，这几个项目经常一起上线，上线过程，先由开发进行打包，然后将几个包发给运行进行发布。我们使用mvn package进行打包，需要在每个项目的pom.xml所在目录都去执行一次这个命令，也就是说需要执行3次，这个电商项目还会涉及到后台系统、bi系统、监控系统等等，可能最后会多达10个小项目，那时候我们每次上线都需要执行10次打包操作，这个过程是相当繁琐的。

那么maven有没有更好的办法来解决这个事情呢？

这个用到的就是我们本次要说的maven中的聚合。

整个电商我们可以作为一个大的系统，上面的pc端、h5微站、api接口、后台系统、bi系统、监控系统都可以作为里面的一个具体比较大一个模块。

我们使用maven聚合功能来实现上面的需求，我们需要创建一个额外的maven项目javacode-aggregator来管理上面3个项目，然后只用在javacode-aggregator项目中执行mvn命令，就会自动为其他3个项目自动执行同样的mvn命令。

Maven聚合

maven聚合需要创建一个新的maven项目，用来管理其他的maven构件模块，新的maven项目中加入如下配置：

<modules>      <module>模块1</module>      <module>模块2</module>      <module>模块n</module>  </modules>  <package>pom</package>

新的项目中执行任何mvn命令，都会modules中包含的所有模块执行同样的命令，而被包含的模块不需要做任何特殊的配置，正常的maven项目就行。注意上面的module元素，这部分是被聚合的模块pom.xml所在目录的相对路径。 package的值必须为pom，这个需要注意。下面看案例。

实操案例

下面过程仔细看了。

创建项目`javacode-aggregator`

打开idea，点击File->New->Project，选择Maven，如下：

点击Next，输入项目坐标信息，如下：

点击Next，输入Project name 为javacode-aggregator，如下：

点击Finish，创建成功，如下：

配置一下idea的maven环境，点击File->Settings，如下图：

删除下面无用的代码：

项目变成了下面这样：

pom.xml中加入下面配置：

<packaging>pom</packaging>

最后pom.xml内容如下：

<?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.javacode2018</groupId>      <artifactId>javacode-aggregator</artifactId>      <version>1.0-SNAPSHOT</version>      <packaging>pom</packaging>    </project>

创建`javacode2018-pc` 模块

注意这里说的是模块，不再是创建项目，过程仔细看。

idea中选中javacode-aggregator

点击File->New->Module，准备创建模块，如下图：

选择Maven，如图：

点击Next，如下：

点击下面的...按钮，选择None，如下：

输入坐标信息，如下：

点击Next，输入Module name :javacode2018-pc，如下：

点击Finish，完成javacode-2018模块的创建，如下：

我们来看一下javacode-aggregator的pom.xml，多了一部分，如下：

注意上面的<packaging>pom</packaging>

创建javacode2018-h5模块

创建步骤和上面javacode2018-pc步骤一样。

创建javacode2018-api模块

创建步骤和上面javacode2018-pc步骤一样。

我们看一下项目最终结构，如下图：

看一下上图中的javacode-aggregator项目的pom.xml，modules元素中多出了3部分。

再来看看其他3个模块的pom文件，和普通的pom.xml一样，如下图：

在javacode-aggregator/pom.xml目录中执行mvn package感受一下效果：

D:codeIdeaProjectsjavacode-aggregator>mvn package  [INFO] Scanning for projects...  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Build Order:  [INFO]  [INFO] javacode2018-pc                                                    [jar]  [INFO] javacode2018-h5                                                    [jar]  [INFO] javacode2018-api                                                   [jar]  [INFO] javacode-aggregator                                                [pom]  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT                              [1/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode-aggregatorjavacode2018-pcsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pc ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode-aggregatorjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-h5 >------------------  [INFO] Building javacode2018-h5 1.0-SNAPSHOT                              [2/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-h5 ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-h5 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-h5 ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode-aggregatorjavacode2018-h5srctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-h5 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-h5 ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-h5 ---  [INFO] Building jar: D:codeIdeaProjectsjavacode-aggregatorjavacode2018-h5targetjavacode2018-h5-1.0-SNAPSHOT.jar  [INFO]  [INFO] -----------------< com.javacode2018:javacode2018-api >------------------  [INFO] Building javacode2018-api 1.0-SNAPSHOT                             [3/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-api ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-api ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-api ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode-aggregatorjavacode2018-apisrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-api ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-api ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-api ---  [INFO] Building jar: D:codeIdeaProjectsjavacode-aggregatorjavacode2018-apitargetjavacode2018-api-1.0-SNAPSHOT.jar  [INFO]  [INFO] ----------------< com.javacode2018:javacode-aggregator >----------------  [INFO] Building javacode-aggregator 1.0-SNAPSHOT                          [4/4]  [INFO] --------------------------------[ pom ]---------------------------------  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Summary for javacode-aggregator 1.0-SNAPSHOT:  [INFO]  [INFO] javacode2018-pc .................................... SUCCESS [  2.542 s]  [INFO] javacode2018-h5 .................................... SUCCESS [  0.195 s]  [INFO] javacode2018-api ................................... SUCCESS [  0.218 s]  [INFO] javacode-aggregator ................................ SUCCESS [  0.024 s]  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  3.223 s  [INFO] Finished at: 2019-11-19T13:28:00+08:00  [INFO] ------------------------------------------------------------------------

我们分析一下上面的输出：

[INFO] Reactor Build Order:  [INFO]  [INFO] javacode2018-pc                                                    [jar]  [INFO] javacode2018-h5                                                    [jar]  [INFO] javacode2018-api                                                   [jar]  [INFO] javacode-aggregator                                                [pom]

上面这个列出了需要构件的maven构件列表及顺序，共有4个构件，3个jar包，1个pom类型的构件。

然后开始按照上面列出的顺序，一个个开始执行mvn package命令，最后4个都执行成功了，我们来看一下最终产生的效果，如下图：

从上图中我们可以看到3个模块都生成了jar包，说明我们执行了一次mvn package，分别在3个模块中都运行了，我们在来执行一下mvn clean清理代码，感受一下最终效果：

D:codeIdeaProjectsjavacode-aggregator>mvn clean  [INFO] Scanning for projects...  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Build Order:  [INFO]  [INFO] javacode2018-pc                                                    [jar]  [INFO] javacode2018-h5                                                    [jar]  [INFO] javacode2018-api                                                   [jar]  [INFO] javacode-aggregator                                                [pom]  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT                              [1/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-pc ---  [INFO] Deleting D:codeIdeaProjectsjavacode-aggregatorjavacode2018-pctarget  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-h5 >------------------  [INFO] Building javacode2018-h5 1.0-SNAPSHOT                              [2/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-h5 ---  [INFO] Deleting D:codeIdeaProjectsjavacode-aggregatorjavacode2018-h5target  [INFO]  [INFO] -----------------< com.javacode2018:javacode2018-api >------------------  [INFO] Building javacode2018-api 1.0-SNAPSHOT                             [3/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-api ---  [INFO] Deleting D:codeIdeaProjectsjavacode-aggregatorjavacode2018-apitarget  [INFO]  [INFO] ----------------< com.javacode2018:javacode-aggregator >----------------  [INFO] Building javacode-aggregator 1.0-SNAPSHOT                          [4/4]  [INFO] --------------------------------[ pom ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode-aggregator ---  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Summary for javacode-aggregator 1.0-SNAPSHOT:  [INFO]  [INFO] javacode2018-pc .................................... SUCCESS [  0.250 s]  [INFO] javacode2018-h5 .................................... SUCCESS [  0.067 s]  [INFO] javacode2018-api ................................... SUCCESS [  0.068 s]  [INFO] javacode-aggregator ................................ SUCCESS [  0.034 s]  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  0.605 s  [INFO] Finished at: 2019-11-19T13:34:42+08:00  [INFO] ------------------------------------------------------------------------

项目结构如下图：

3个项目中的target都被清理掉了，是不是感觉很爽。

上面介绍了pom.xml中的module元素的值为被聚合的模块pom.xml所在的目录路径，可以是相对路径，也可以是绝对路径，上面演示的是相对路径，大家可以自己去玩一下绝对路径的情况。

聚合的功能中，聚合模块的pom.xml中通过modules->module来引用被聚合的模块，被聚合的模块是不用感知自己被聚合了，所以被聚合的模块中pom.xml中是不知道javacode-aggregator的存在的。

继承

需求

细心的朋友已经发现了javacode2018-pc、javacode2018-h5、javacode2018-api3个项目的groupId、version都是一样的。还有这几个项目准备都是用springmvc、mybatis开发的，所以需要引入依赖如下：

<dependency>      <groupId>org.springframework</groupId>      <artifactId>spring-web</artifactId>      <version>5.2.1.RELEASE</version>  </dependency>  <dependency>      <groupId>org.mybatis</groupId>      <artifactId>mybatis-spring</artifactId>      <version>2.0.3</version>  </dependency>

3个项目中出现了同样的配置，一个配置出现了多份，作为开发者，我想你们和我一样，是无法接受的，必须要寻求一些方法来解决，需要将公共的部分提取出来共用。

maven也为我们考虑到了这种情况，maven中使用继承来解决这个问题。

继承的实现

操作分为3步骤：

创建一个父maven构件，将依赖信息放在pom.xml中 <dependencies> <dependency>依赖的构件的坐标信息</dependency> <dependency>依赖的构件的坐标信息</dependency> <dependency>依赖的构件的坐标信息</dependency> </dependencies>
将父构件的package元素的值置为pom <packaging>pom</packaging>
在子构件的pom.xml引入父构件的配置： <parent> <groupId>父构件groupId</groupId> <artifactId>父构件artifactId</artifactId> <version>父构件的版本号</version> <relativePath>父构件pom.xml路径</relativePath> </parent>

relativePath表示父构件pom.xml相对路径，默认是../pom.xml，所以一般情况下父子结构的maven构件在目录结构上一般也采用父子关系。

实操案例

先创建一个父项目javacode-parent，坐标信息如下：

<groupId>com.javacode2018</groupId>  <artifactId>javacode2018-parent</artifactId>  <version>1.0-SNAPSHOT</version>

创建过程大家已经轻车熟路了，就不演示了，最终如下图：

删除无用的2目录.idea和src

创建子模块`javacode2018-pc` 模块

注意这里说的是模块了，不在是创建项目了，过程仔细看。

idea中选中javacode-parent，如下图：

点击File->New->Module，准备创建模块，如下图：

选中Maven，如下图：

点击Next，这个页面需要注意了，默认如下图：

此时我们点击第一个...按钮，这个按钮是设置聚合的，所以选中None，如下图：

变成了下面这样：

输入构件信息，如下图：

点击Next，输入Module-name的值为javacode2018-pc，如下图：

点击Finish完成创建操作，如下图：

上图中，看一下javacode2018-pc的pom.xml，多了个parent元素，并且这个pom.xml中构件的groupId、version都没有了，这个pom.xml继承了javacode2018-parent/pom.xml中的内容，他们的groupId、version都是一样的，子构件可以从父pom.xml中继承这些内容，所以如果是一样的情况，可以不写。

创建另外两个子模块javacode2018-h5、javacode2018-api

步骤参考javacode2018-pc模块的创建过程。

最终项目如下图：

下面我们来看一下4个pom.xml的内容。

javacode2018-parent/pom.xml的内容：

<?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.javacode2018</groupId>      <artifactId>javacode2018-parent</artifactId>      <version>1.0-SNAPSHOT</version>    </project>

javacode2018-pc/pom.xml的内容：

<?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">      <parent>          <artifactId>javacode2018-parent</artifactId>          <groupId>com.javacode2018</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>javacode2018-pc</artifactId>    </project>

javacode2018-h5/pom.xml的内容：

<?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">      <parent>          <artifactId>javacode2018-parent</artifactId>          <groupId>com.javacode2018</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>javacode2018-h5</artifactId>    </project>

javacode2018-api/pom.xml的内容：

<?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">      <parent>          <artifactId>javacode2018-parent</artifactId>          <groupId>com.javacode2018</groupId>          <version>1.0-SNAPSHOT</version>      </parent>      <modelVersion>4.0.0</modelVersion>        <artifactId>javacode2018-api</artifactId>    </project>

我们在父构件javacode2018-parent/pom.xml中加入下面配置：

<packaging>pom</packaging>  <dependencies>      <dependency>          <groupId>org.springframework</groupId>          <artifactId>spring-web</artifactId>          <version>5.2.1.RELEASE</version>      </dependency>      <dependency>          <groupId>org.mybatis</groupId>          <artifactId>mybatis-spring</artifactId>          <version>2.0.3</version>      </dependency>  </dependencies>

使用下面命令在javacode2018-parent/pom.xml所在目录看一下javacode2018-parent构件依赖情况:

D:codeIdeaProjectsjavacode2018-parent>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ----------------< com.javacode2018:javacode2018-parent >-----------------  [INFO] Building javacode2018-parent 1.0-SNAPSHOT  [INFO] --------------------------------[ pom ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-parent ---  [INFO] com.javacode2018:javacode2018-parent:pom:1.0-SNAPSHOT  [INFO] +- org.springframework:spring-web:jar:5.2.1.RELEASE:compile  [INFO] |  +- org.springframework:spring-beans:jar:5.2.1.RELEASE:compile  [INFO] |  - org.springframework:spring-core:jar:5.2.1.RELEASE:compile  [INFO] |     - org.springframework:spring-jcl:jar:5.2.1.RELEASE:compile  [INFO] - org.mybatis:mybatis-spring:jar:2.0.3:compile  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.544 s  [INFO] Finished at: 2019-11-19T14:58:21+08:00  [INFO] ------------------------------------------------------------------------

mvn dependency:tree 这个插件可以根据pom.xml的配置，列出构件的依赖树信息。

我们再来看看javacode2018-pc/pom.xml构件的依赖信息：

D:codeIdeaProjectsjavacode2018-parent>cd javacode2018-pc    D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-pc ---  [INFO] com.javacode2018:javacode2018-pc:jar:1.0-SNAPSHOT  [INFO] +- org.springframework:spring-web:jar:5.2.1.RELEASE:compile  [INFO] |  +- org.springframework:spring-beans:jar:5.2.1.RELEASE:compile  [INFO] |  - org.springframework:spring-core:jar:5.2.1.RELEASE:compile  [INFO] |     - org.springframework:spring-jcl:jar:5.2.1.RELEASE:compile  [INFO] - org.mybatis:mybatis-spring:jar:2.0.3:compile  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.093 s  [INFO] Finished at: 2019-11-19T14:59:34+08:00  [INFO] ------------------------------------------------------------------------

从上图中可以看到javacode2018-pc依赖的jar和父构件javacode2019-parent的一样，说明从父类继承了这些依赖。其他2个子构件，大家也可以去看一下，依赖关系都从父构件继承过来了。

relativePath元素

上面演示的父构件和子构件的目录结构刚好符合父子关系，如果父构件和子构件的目录不是父子关系，比如都位于同等级别的目录或者位于更复杂的目录的时候，此时我们需要在子pom.xml的parent元素中使用relativePath元素来指定父pom.xml相对路径位置，这个值我们上面没有指定，默认是../pom.xml，表示父pom.xml位于子pom.xml的上一级目录，我们的模块刚好符合这种关系，所以这个值省略了。

正确的设置relativePath是非常重要的，这个需要注意，子模块中执行mvn命令的时候，会去找父pom.xml的配置，会先通过relativePath指定的路径去找，如果找不到，会尝试通过坐标在本地仓库进行查找，如果本地找不到，会去远程仓库找，如果远程仓库也没有，会报错。

可以通过继承的元素有以下这些

上面我们看到了groupId、version、dependency中的依赖在子pom.xml中都没有写，这些都是从父pom.xml中继承过来的，还有很多元素也可以被继承过来，下面我们列个清单：

groupId：项目组ID，项目坐标的核心元素
version：项目版本，项目坐标的核心元素
description：项目的描述信息
organization：项目的组织信息
inceptionYear：项目的创始年份
url：项目的url地址
developers：项目的开发者信息
contributors：项目的贡献者信息
distributionManagement：项目的部署配置信息
issueManagement：项目的缺陷跟踪系统信息
ciManagement：项目的持续集成系统信息
scm：项目的版本控制系统信息
mailingLists：项目的邮件列表信息
properties：自定义的maven属性配置信息
dependencyManagement：项目的依赖管理配置
repositories：项目的仓库配置
build：包括项目的源码目录配置、输出目录配置、插件管理配置等信息
reporting：包括项目的报告输出目录配置、报告插件配置等信息

依赖管理(dependencyManagement)

大家是否发现了，上面的继承存在的一个问题，如果我在新增一个子构件，都会默认从父构件中继承依赖的一批构建，父pom.xml中配置的这些依赖的构建可能是其他项目不需要的，可能某个子项目只是想使用其中一个构件，但是上面的继承关系却把所有的依赖都给传递到子构件中了，这种显然是不合适的。

maven中也考虑到了这种情况，可以使用dependencyManagement元素来解决这个问题。

maven提供的dependencyManagement元素既能让子模块继承到父模块的依赖配置，又能保证子模块依赖使用的灵活性，在dependencyManagement元素下声明的依赖不会引入实际的依赖，他只是声明了这些依赖，不过它可以对dependencies中使用的依赖起到一些约束作用。

修改javacode2018-parent/pom.xml配置如下：

<?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.javacode2018</groupId>      <artifactId>javacode2018-parent</artifactId>      <version>1.0-SNAPSHOT</version>        <packaging>pom</packaging>        <dependencyManagement>          <dependencies>              <dependency>                  <groupId>org.springframework</groupId>                  <artifactId>spring-web</artifactId>                  <version>5.2.1.RELEASE</version>              </dependency>              <dependency>                  <groupId>org.mybatis</groupId>                  <artifactId>mybatis-spring</artifactId>                  <version>2.0.3</version>              </dependency>          </dependencies>      </dependencyManagement>    </project>

可以看到我们将dependencies配置移到dependencyManagement下面了。

我们使用下面命令看一下项目的依赖情况：

D:codeIdeaProjectsjavacode2018-parent>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ----------------< com.javacode2018:javacode2018-parent >-----------------  [INFO] Building javacode2018-parent 1.0-SNAPSHOT  [INFO] --------------------------------[ pom ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-parent ---  [INFO] com.javacode2018:javacode2018-parent:pom:1.0-SNAPSHOT  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.756 s  [INFO] Finished at: 2019-11-19T15:44:52+08:00  [INFO] ------------------------------------------------------------------------    D:codeIdeaProjectsjavacode2018-parent>cd javacode2018-pc    D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-pc ---  [INFO] com.javacode2018:javacode2018-pc:jar:1.0-SNAPSHOT  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.676 s  [INFO] Finished at: 2019-11-19T15:45:08+08:00  [INFO] ------------------------------------------------------------------------

父子构件中都看不到依赖的jar包了，说明父pom.xml中dependencyManagement这些依赖的构建没有被子模块依赖进去。

子模块如果想用到这些配置，可以dependencies进行引用，引用之后，依赖才会真正的起效。

在在3个子模块的pom.xml中加入下面配置：

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

我们在运行一下上面的3个命令，看效果：

D:codeIdeaProjectsjavacode2018-parent>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ----------------< com.javacode2018:javacode2018-parent >-----------------  [INFO] Building javacode2018-parent 1.0-SNAPSHOT  [INFO] --------------------------------[ pom ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-parent ---  [INFO] com.javacode2018:javacode2018-parent:pom:1.0-SNAPSHOT  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.759 s  [INFO] Finished at: 2019-11-19T15:48:28+08:00  [INFO] ------------------------------------------------------------------------    D:codeIdeaProjectsjavacode2018-parent>cd javacode2018-pc    D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn dependency:tree  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ javacode2018-pc ---  [INFO] com.javacode2018:javacode2018-pc:jar:1.0-SNAPSHOT  [INFO] +- org.springframework:spring-web:jar:5.2.1.RELEASE:compile  [INFO] |  +- org.springframework:spring-beans:jar:5.2.1.RELEASE:compile  [INFO] |  - org.springframework:spring-core:jar:5.2.1.RELEASE:compile  [INFO] |     - org.springframework:spring-jcl:jar:5.2.1.RELEASE:compile  [INFO] - org.mybatis:mybatis-spring:jar:2.0.3:compile  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.875 s  [INFO] Finished at: 2019-11-19T15:48:38+08:00  [INFO] ------------------------------------------------------------------------

javacode2018-parent构件中没有列出依赖信息，而javacode2018-pc列出了依赖信息。

大家看一下下面的截图：

注意上面的红框中依赖的构建没有version，左边2个红圈中的2个向上的箭头，表示这个是从父pom.xml中传递过来的，所以version可以省略。

再看一下父pom.xml截图效果：

dependencyManagement中定义了依赖的构建，2个向下的箭头表示被子模块有继承。

dependencyManagement不会引入实际的依赖，只有在子类中使用dependency来引入父dependencyManagement声明的依赖之后，依赖的构建才会被真正的引入。

使用dependencyManagement来解决继承的问题，子pom.xml中只用写groupId,artifactId就可以了，其他信息都会从父dependencyManagement中声明的依赖关系中传递过来，通常我们使用这种方式将所有依赖的构建在父pom.xml中定义好，子构件中只需要通过groupId,artifactId就可以引入依赖的构建，而不需要写version，可以很好的确保多个子项目中依赖构件的版本的一致性，对应依赖构件版本的升级也非常方便，只需要在父pom.xml中修改一下就可以了。

单继承问题

存在的问题及解决方案

上面讲解了dependencyManagement的使用，但是有个问题，只有使用继承的时候，dependencyManagement中声明的依赖才可能被子pom.xml用到，如果我的项目本来就有父pom.xml了，但是我现在想使用另外一个项目dependencyManagement中声明的依赖，此时我们怎么办？这就是单继承的问题，这种情况在spring-boot、spring-cloud中会遇到，所以大家需要注意，这块一定需要玩转。

当我们想在项目中使用另外一个构件中dependencyManagement声明的依赖，而又不想继承这个项目的时候，可以在我们的项目中使用加入下面配置：

<dependencyManagement>      <dependencies>          <dependency>              <groupId>com.javacode2018</groupId>              <artifactId>javacode2018-parent</artifactId>              <version>1.0-SNAPSHOT</version>              <type>pom</type>              <scope>import</scope>          </dependency>          <dependency>构件2</dependency>          <dependency>构件3</dependency>          <dependency>构件n</dependency>      </dependencies>  </dependencyManagement>

上面这个配置会将javacode2018-parent构件中dependencyManagement元素中声明的所有依赖导入到当前pom.xml的dependencyManagement中，相当于把下面部分的内容：

<dependency>      <groupId>com.javacode2018</groupId>      <artifactId>javacode2018-parent</artifactId>      <version>1.0-SNAPSHOT</version>      <type>pom</type>      <scope>import</scope>  </dependency>

替换成了javacode2018-parent/pom.xml中dependencyManagement元素内容，替换之后变成：

<dependencyManagement>      <dependencies>          <dependency>              <groupId>org.springframework</groupId>              <artifactId>spring-web</artifactId>              <version>5.2.1.RELEASE</version>          </dependency>          <dependency>              <groupId>org.mybatis</groupId>              <artifactId>mybatis-spring</artifactId>              <version>2.0.3</version>          </dependency>          <dependency>构件2</dependency>          <dependency>构件3</dependency>          <dependency>构件n</dependency>      </dependencies>  </dependencyManagement>

实操案例

创建项目javacode2018-pom-import，具体过程不演示了，坐标信息：

<groupId>com.javacode2018</groupId>  <artifactId>javacode2018-pom-import</artifactId>  <version>1.0-SNAPSHOT</version>

创建完毕之后，如下图：

修改javacode2018-pom-import/pom.xml内容，如下：

<?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.javacode2018</groupId>      <artifactId>javacode2018-pom-import</artifactId>      <version>1.0-SNAPSHOT</version>        <dependencyManagement>          <dependencies>              <dependency>                  <groupId>com.alibaba</groupId>                  <artifactId>fastjson</artifactId>                  <version>1.2.62</version>              </dependency>              <dependency>                  <groupId>junit</groupId>                  <artifactId>junit</artifactId>                  <version>4.12</version>                  <scope>test</scope>              </dependency>          </dependencies>      </dependencyManagement>    </project>

上面我们在dependencyManagement中声明了2个依赖：fastjson和junit。

在javacode2018-pom-import/pom.xml中执行mvn install将其安装到本地仓库

D:codeIdeaProjectsjavacode2018-pom-import>mvn install  [INFO] Scanning for projects...  [INFO]  [INFO] --------------< com.javacode2018:javacode2018-pom-import >--------------  [INFO] Building javacode2018-pom-import 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pom-import ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pom-import ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pom-import ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-pom-importsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pom-import ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pom-import ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pom-import ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-pom-importtargetjavacode2018-pom-import-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pom-import ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-pom-importtargetjavacode2018-pom-import-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pom-import1.0-SNAPSHOTjavacode2018-pom-import-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-pom-importpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-pom-import1.0-SNAPSHOTjavacode2018-pom-import-1.0-SNAPSHOT.pom  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.692 s  [INFO] Finished at: 2019-11-19T17:23:16+08:00  [INFO] ------------------------------------------------------------------------

现在我们想在javacode2018-pc/pom.xml中使用javacode2018-pom-import/pom.xml的dependencyManagement元素中定义的fastjson和junit的依赖，而我们的javacode2019-pc已经继承了javacode-parent了，maven中只能单继承，所以没法通过继承的方式来实现了，那么我们可以在javacode2019-pc/pom.xml中加入下面配置：

<dependencyManagement>      <dependencies>          <dependency>              <groupId>com.javacode2018</groupId>              <artifactId>javacode2018-pom-import</artifactId>              <version>1.0-SNAPSHOT</version>              <type>pom</type>              <scope>import</scope>          </dependency>      </dependencies>  </dependencyManagement>

此时可以使用fastjson的依赖了，javacode2018-pc/pom.xml中project->dependencies元素中加入下面配置：

<dependency>      <groupId>com.alibaba</groupId>      <artifactId>fastjson</artifactId>  </dependency>

看一下效果：

上面的fastjson没有指定版本号，直接可以使用，说明从javacode2018-pom-import传递过来了。

可以点击一下上面红圈中的箭头，会跳到本地仓库的javacode2018-pom-import-1.0-SNAPSHOT.pom文件，如下：

插件管理(pluginManagement)

maven中提供了dependencyManagement来解决继承的问题，同样也提供了解决插件继承问题的pluginManagement元素，在父pom中可以在这个元素中声明插件的配置信息，但是子pom.xml中不会引入此插件的配置信息，只有在子pom.xml中使用plugins->plugin元素正在引入这些声明的插件的时候，插件才会起效，子插件中只需要写groupId、artifactId，其他信息都可以从父构件中传递过来。

实操案例

在javacode2018-parent/pom.xml中加入下面配置：

<build>      <pluginManagement>          <plugins>              <plugin>                  <groupId>org.apache.maven.plugins</groupId>                  <artifactId>maven-source-plugin</artifactId>                  <version>3.2.0</version>                  <executions>                      <execution>                          <id>attach-source</id>                          <phase>verify</phase>                          <goals>                              <goal>jar-no-fork</goal>                          </goals>                      </execution>                  </executions>              </plugin>          </plugins>      </pluginManagement>  </build>

maven-source-plugin这个插件在上一章有介绍过，源码打包的。上面是将插件maven-source-plugin的jar-no-fork目标绑定在default生命周期的verify阶段，verify阶段会在default生命周期的install周期前面执行。下面我们看效果。

在javacode2018-pc/pom.xml所在目录运行下面命令

D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn clean install  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-pc ---  [INFO] Deleting D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctarget  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pc ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.pom  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.254 s  [INFO] Finished at: 2019-11-19T16:24:39+08:00  [INFO] ------------------------------------------------------------------------

mvn clean install 会清理代码，然后将打包构件，将构建安装到本地仓库，从输入中可以看到javacode2018-pc-1.0-SNAPSHOT.jar被安装到本地仓库了。但是没有看到打包源码的插件的运行，说明了javacode2018-pc没有从父pom.xml中继承插件的配置信息，所以插件配置没有起效，现在我们要让插件起效，继续看：

在javacode2018-pc/pom.xml中加入下面配置：

<build>      <plugins>          <plugin>              <groupId>org.apache.maven.plugins</groupId>              <artifactId>maven-source-plugin</artifactId>          </plugin>      </plugins>  </build>

截图看效果：

又一个线上的箭头，说明这个是从父pom.xml中传递过来了，大家仔细看一下上面的配置，插件只写了groupId、artifactId，其他信息都没有写，其他信息都可以从父pom.xml中传递过来，下面我们看一下插件是否起效了，运行下面命令，见证奇迹：

D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn clean install  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-pc ---  [INFO] Deleting D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctarget  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pc ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-source-plugin:3.2.0:jar-no-fork (attach-source) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT-sources.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.pom  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT-sources.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT-sources.jar  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.477 s  [INFO] Finished at: 2019-11-19T16:28:18+08:00  [INFO] ------------------------------------------------------------------------

注意上面的输出中有attach-source，这个就是上面我们插件任务的id，输出中还有javacode2018-pc-1.0-SNAPSHOT-sources.jar信息，说明源码也是打包成功了，最后也是上传到了本地仓库了。

上面演示了只用在子pom.xml中写上插件的groupId、artifactId就可以了，其他信息会从父pom.xml中插件的定义中传递过来，而子pom.xml中也可以自定义插件的这些配置，修改javacode2018-pc/pom.xml配置，如下：

<build>      <plugins>          <plugin>              <groupId>org.apache.maven.plugins</groupId>              <artifactId>maven-source-plugin</artifactId>              <executions>                  <execution>                      <id>attach-source</id>                      <goals>                          <goal>help</goal>                      </goals>                  </execution>              </executions>          </plugin>      </plugins>  </build>

再看一下效果：

D:codeIdeaProjectsjavacode2018-parentjavacode2018-pc>mvn clean install  [INFO] Scanning for projects...  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >-------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ javacode2018-pc ---  [INFO] Deleting D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctarget  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pc ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-source-plugin:3.2.0:help (attach-source) @ javacode2018-pc ---  [INFO] Apache Maven Source Plugin 3.2.0    The Maven Source Plugin creates a JAR archive of the source files of the    current project.    This plugin has 7 goals:    source:aggregate    Aggregate sources for all modules in an aggregator project.    source:generated-test-jar    This plugin bundles all the test sources into a jar archive.    source:help    Display help information on maven-source-plugin.    Call mvn source:help -Ddetail=true -Dgoal=<goal-name> to display parameter    details.    source:jar    This plugin bundles all the sources into a jar archive.    source:jar-no-fork    This goal bundles all the sources into a jar archive. This goal functions the    same as the jar goal but does not fork the build and is suitable for attaching    to the build lifecycle.    source:test-jar    This plugin bundles all the test sources into a jar archive.    source:test-jar-no-fork    This goal bundles all the test sources into a jar archive. This goal functions    the same as the test-jar goal but does not fork the build, and is suitable for    attaching to the build lifecycle.      [INFO]  [INFO] --- maven-source-plugin:3.2.0:jar-no-fork (attach-source) @ javacode2018-pc ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT-sources.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.pom  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT-sources.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT-sources.jar  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  2.752 s  [INFO] Finished at: 2019-11-19T16:41:21+08:00  [INFO] ------------------------------------------------------------------------

输出中有下面2行：

[INFO] --- maven-source-plugin:3.2.0:help (attach-source) @ javacode2018-pc ---  [INFO] --- maven-source-plugin:3.2.0:jar-no-fork (attach-source) @ javacode2018-pc ---

说明maven-source-plugin插件执行了2个目标：help和jar-no-fork。此时父子pom.xml中插件配置信息合并了，所以出现了2个目标。具体最终javacode2018-pc/pom.xml中的内容是什么样的，可以通过下面这个命令看到：

mvn help:effective-pom

上面这个命令大家最好去看一下效果，当pom.xml中存在复杂的关系的时候，可以通过这个命令解析得到这个构件最终pom.xml的内容。

聚合与继承的关系

前面已经详解了聚合和继承，想必大家对这块也有了自己的理解。

聚合主要是为了方便多模块快速构建。

而继承主要是为了重用相同的配置。

对于聚合来说，聚合模块是知道被聚合模块的存在的，而被聚合模块是感知不到聚合模块的存在。

对于继承来说，父构件是感知不到子构件的存在，而子构件需要使用parent来引用父构件。

两者的共同点是，聚合模块和继承中的父模块的package属性都必须是pom类型的，同时，聚合模块和父模块中的除了pom.xml，一般都是没有什么内容的。

实际使用是，我们经常将聚合和继承一起使用，能同时使用到两者的优点。

下面我们在javacode2018-parent中加入聚合的配置：

<modules>      <module>javacode2018-pc</module>      <module>javacode2018-h5</module>      <module>javacode2018-api</module>  </modules>

javacode20180-parent/pom.xml目录运行一下mvn install，看看效果：

D:codeIdeaProjectsjavacode2018-parent>mvn install  [INFO] Scanning for projects...  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Build Order:  [INFO]  [INFO] javacode2018-parent                                                [pom]  [INFO] javacode2018-pc                                                    [jar]  [INFO] javacode2018-h5                                                    [jar]  [INFO] javacode2018-api                                                   [jar]  [INFO]  [INFO] ----------------< com.javacode2018:javacode2018-parent >----------------  [INFO] Building javacode2018-parent 1.0-SNAPSHOT                          [1/4]  [INFO] --------------------------------[ pom ]---------------------------------  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-parent ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-parent1.0-SNAPSHOTjavacode2018-parent-1.0-SNAPSHOT.pom  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-pc >------------------  [INFO] Building javacode2018-pc 1.0-SNAPSHOT                              [2/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-pc ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcsrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-pc ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-pc ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-pc ---  [INFO]  [INFO] --- maven-source-plugin:3.2.0:help (attach-source) @ javacode2018-pc ---  [INFO] Apache Maven Source Plugin 3.2.0    The Maven Source Plugin creates a JAR archive of the source files of the    current project.    This plugin has 7 goals:    source:aggregate    Aggregate sources for all modules in an aggregator project.    source:generated-test-jar    This plugin bundles all the test sources into a jar archive.    source:help    Display help information on maven-source-plugin.    Call mvn source:help -Ddetail=true -Dgoal=<goal-name> to display parameter    details.    source:jar    This plugin bundles all the sources into a jar archive.    source:jar-no-fork    This goal bundles all the sources into a jar archive. This goal functions the    same as the jar goal but does not fork the build and is suitable for attaching    to the build lifecycle.    source:test-jar    This plugin bundles all the test sources into a jar archive.    source:test-jar-no-fork    This goal bundles all the test sources into a jar archive. This goal functions    the same as the test-jar goal but does not fork the build, and is suitable for    attaching to the build lifecycle.      [INFO]  [INFO] --- maven-source-plugin:3.2.0:jar-no-fork (attach-source) @ javacode2018-pc ---  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pcpom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT.pom  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-pctargetjavacode2018-pc-1.0-SNAPSHOT-sources.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-pc1.0-SNAPSHOTjavacode2018-pc-1.0-SNAPSHOT-sources.jar  [INFO]  [INFO] ------------------< com.javacode2018:javacode2018-h5 >------------------  [INFO] Building javacode2018-h5 1.0-SNAPSHOT                              [3/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-h5 ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-h5 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-h5 ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-h5srctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-h5 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-h5 ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-h5 ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-h5targetjavacode2018-h5-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-h5 ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-h5targetjavacode2018-h5-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-h51.0-SNAPSHOTjavacode2018-h5-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-h5pom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-h51.0-SNAPSHOTjavacode2018-h5-1.0-SNAPSHOT.pom  [INFO]  [INFO] -----------------< com.javacode2018:javacode2018-api >------------------  [INFO] Building javacode2018-api 1.0-SNAPSHOT                             [4/4]  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ javacode2018-api ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ javacode2018-api ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ javacode2018-api ---  [WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!  [INFO] skip non existing resourceDirectory D:codeIdeaProjectsjavacode2018-parentjavacode2018-apisrctestresources  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ javacode2018-api ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ javacode2018-api ---  [INFO] No tests to run.  [INFO]  [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ javacode2018-api ---  [INFO] Building jar: D:codeIdeaProjectsjavacode2018-parentjavacode2018-apitargetjavacode2018-api-1.0-SNAPSHOT.jar  [INFO]  [INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-api ---  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-apitargetjavacode2018-api-1.0-SNAPSHOT.jar to C:UsersThink.m2repositorycomjavacode2018javacode2018-api1.0-SNAPSHOTjavacode2018-api-1.0-SNAPSHOT.jar  [INFO] Installing D:codeIdeaProjectsjavacode2018-parentjavacode2018-apipom.xml to C:UsersThink.m2repositorycomjavacode2018javacode2018-api1.0-SNAPSHOTjavacode2018-api-1.0-SNAPSHOT.pom  [INFO] ------------------------------------------------------------------------  [INFO] Reactor Summary for javacode2018-parent 1.0-SNAPSHOT:  [INFO]  [INFO] javacode2018-parent ................................ SUCCESS [  0.416 s]  [INFO] javacode2018-pc .................................... SUCCESS [  2.654 s]  [INFO] javacode2018-h5 .................................... SUCCESS [  0.262 s]  [INFO] javacode2018-api ................................... SUCCESS [  0.225 s]  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  3.827 s  [INFO] Finished at: 2019-11-19T17:51:42+08:00  [INFO] ------------------------------------------------------------------------

上篇文章中留下的2个问题

问题1

下面这个配置是干什么的？给哪个插件使用的？

<properties>      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>  </properties>

编译代码的时候，涉及到资源文件和测试资源文件的拷贝，拷贝文件的时候涉及到文件的编码，这个是设置文件的编码为UTF-8格式的。

我们在上篇文章的maven-chat06项目的目录中执行mvn compile命令，效果如下：

D:codeIdeaProjectsmaven-chat06>mvn compile  [INFO] Scanning for projects...  [INFO]  [INFO] -------------------< com.javacode2018:maven-chat06 >--------------------  [INFO] Building maven-chat06 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-chat06 ---  [INFO] Using 'UTF-8' encoding to copy filtered resources.  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-chat06 ---  [INFO] Nothing to compile - all classes are up to date  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.179 s  [INFO] Finished at: 2019-11-19T17:57:27+08:00  [INFO] ------------------------------------------------------------------------

可以看到上面有这样的输出：

[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-chat06 ---  [INFO] Using 'UTF-8' encoding to copy filtered resources.

从上面可以看出maven-resources-plugin插件的resources目标中会使用这个编码的配置，我们来看一下这个目标具体参数配置，我们截取了部分输出，如下：

D:codeIdeaProjectsmaven-chat06>mvn help:describe -Dplugin=resources -Dgoal=resources  -Ddetail  [INFO] Scanning for projects...  [INFO]  [INFO] -------------------< com.javacode2018:maven-chat06 >--------------------  [INFO] Building maven-chat06 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ maven-chat06 ---  [INFO] Mojo: 'resources:resources'  resources:resources    Description: Copy resources for the main source code to the main output      directory. Always uses the project.build.resources element to specify the      resources to copy.    Implementation: org.apache.maven.plugin.resources.ResourcesMojo    Language: java    Bound to phase: process-resources      Available parameters:        delimiters        Set of delimiters for expressions to filter within the resources. These        delimiters are specified in the form 'beginToken*endToken'. If no '*' is        given, the delimiter is assumed to be the same for start and end.          So, the default filtering delimiters might be specified as:          <delimiters>         <delimiter>${*}</delimiter>         <delimiter>@</delimiter>        </delimiters>          Since the '@' delimiter is the same on both ends, we don't need to        specify '@*@' (though we can).        encoding (Default: ${project.build.sourceEncoding})        User property: encoding        The character encoding scheme to be applied when filtering resources.

注意上面输出中最后的一部分，如下：

    encoding (Default: ${project.build.sourceEncoding})        User property: encoding        The character encoding scheme to be applied when filtering resources.

encoding这个参数用来指定编码的，默认值是${project.build.sourceEncoding}，也可以通过encoding用户属性来设置。

所以这个设置编码的还有下面3种写法，共四种：

pom.xml中2种：  <encoding>UTF-8</encoding>  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    mvn命令中2种：  mvn compile -Dencoding=UTF-8  mvn compile -Dproject.build.sourceEncoding=UTF-8

问题2

mvn test运行测试用例的时候，测试用例类名的写法默认是有规则的，这些规则有人知道么？从哪里可以看到这些规则？如何自定义？

我们在上一篇中的maven-chat06项目中执行mvn test，看看效果：

D:codeIdeaProjectsmaven-chat06>mvn test  [INFO] Scanning for projects...  [INFO]  [INFO] -------------------< com.javacode2018:maven-chat06 >--------------------  [INFO] Building maven-chat06 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-chat06 ---  [INFO] Using 'UTF-8' encoding to copy filtered resources.  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-chat06 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ maven-chat06 ---  [INFO] Using 'UTF-8' encoding to copy filtered resources.  [INFO] Copying 0 resource  [INFO]  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ maven-chat06 ---  [INFO] Nothing to compile - all classes are up to date  [INFO]  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ maven-chat06 ---  [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  1.411 s  [INFO] Finished at: 2019-11-19T18:07:52+08:00  [INFO] ------------------------------------------------------------------------

可以看到下面这行：

[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ maven-chat06 ---

表示运行测试使用的是插件maven-surefire-plugin的test目标。

我们看看这个目标详细参数，只列出部分信息，如下：

D:codeIdeaProjectsmaven-chat06>mvn help:describe -Dplugin=surefire -Dgoal=test -Ddetail  [INFO] Scanning for projects...  [INFO]  [INFO] -------------------< com.javacode2018:maven-chat06 >--------------------  [INFO] Building maven-chat06 1.0-SNAPSHOT  [INFO] --------------------------------[ jar ]---------------------------------  [INFO]  [INFO] --- maven-help-plugin:3.2.0:describe (default-cli) @ maven-chat06 ---  [INFO] Mojo: 'surefire:test'  surefire:test    Description: Run tests using Surefire.    Implementation: org.apache.maven.plugin.surefire.SurefirePlugin    Language: java    Bound to phase: test      Available parameters:        includes        A list of <include> elements specifying the tests (by pattern) that        should be included in testing. When not specified and when the test        parameter is not specified, the default includes will be        <includes>         <include>**/IT*.java</include>         <include>**/*IT.java</include>         <include>**/*ITCase.java</include>        </includes>        Each include item may also contain a comma-separated sublist of items,        which will be treated as multiple  <include> entries.        This parameter is ignored if the TestNG suiteXmlFiles parameter is        specified.      [INFO] ------------------------------------------------------------------------  [INFO] BUILD SUCCESS  [INFO] ------------------------------------------------------------------------  [INFO] Total time:  4.458 s  [INFO] Finished at: 2019-11-19T18:10:09+08:00  [INFO] ------------------------------------------------------------------------

可以看到上面有个includes参数，可以用来配置需要运行的测试用例，可以配置通配符的方式。

上面还有一段信息：

 Implementation: org.apache.maven.plugin.surefire.SurefirePlugin

上面这部分列出了这个目标的具体实现类是SurefirePlugin。

那么我们可以到本地仓库中看一下这个构件的源码，构件的坐标是：

<groupId>org.apache.maven.plugins</groupId>  <artifactId>maven-surefire-plugin</artifactId>  <version>2.12.4</version>

打开org.apache.maven.plugin.surefire.SurefirePlugin的源码，会找到下面代码：

protected String[] getDefaultIncludes()  {      return new String[]{ "**/Test*.java", "**/*Test.java", "**/*TestCase.java" };  }

这部分代码就是我们测试用例默认需要满足的格式，你创建的测试用例默认情况下必须满足上面这3种格式，否则，测试用例不会被mvn test执行。

总结

需要掌握聚合的使用
掌握继承的使用
掌握单继承问题解决方案
掌握依赖管理和插件管理的使用

还是那句话，建议大家下去了多练练，都操作一遍，加深理解！