原创

Maven系列第7篇:聚合、继承、单继承问题详解,必备技能!

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

  1. maven中聚合详解
  2. maven中继承详解
  3. pom.xml中parent元素的使用详解
  4. pom.xml中dependencyManagement元素使用详解
  5. pom.xml中pluginManagement元素使用详解
  6. 单继承存在的问题及解决方案详解(springboot,springcloud中会常用)
  7. 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:

file

点击Next,输入项目坐标信息,如下:

file

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

file

点击Finish,创建成功,如下:

file

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

file

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-h5javacode2018-api,创建完成之后,另外2个项目如下图:

file

file

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:

file

点击Next,输入项目坐标信息,如下:

file

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

file

点击Finish,创建成功,如下:

file

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

file

删除下面无用的代码:

file

项目变成了下面这样:

file

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

file

点击File->New->Module,准备创建模块,如下图:

file

选择Maven,如图:

file

点击Next,如下:

file

点击下面的...按钮,选择None,如下:

file

file

file

输入坐标信息,如下:

file

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

file

点击Finish,完成javacode-2018模块的创建,如下:

file

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

file

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:

file

看一下上图中的javacode-aggregator项目的pom.xmlmodules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:

file

file

file

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

D:\code\IdeaProjects\javacode-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:\code\IdeaProjects\javacode-aggregator\javacode2018-pc\src\test\resources
[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:\code\IdeaProjects\javacode-aggregator\javacode2018-pc\target\javacode2018-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:\code\IdeaProjects\javacode-aggregator\javacode2018-h5\src\test\resources
[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:\code\IdeaProjects\javacode-aggregator\javacode2018-h5\target\javacode2018-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:\code\IdeaProjects\javacode-aggregator\javacode2018-api\src\test\resources
[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:\code\IdeaProjects\javacode-aggregator\javacode2018-api\target\javacode2018-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:

file

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:\code\IdeaProjects\javacode-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:\code\IdeaProjects\javacode-aggregator\javacode2018-pc\target
[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:\code\IdeaProjects\javacode-aggregator\javacode2018-h5\target
[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:\code\IdeaProjects\javacode-aggregator\javacode2018-api\target
[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:

file

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:

  1. 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>
    
  2. 将父构件的package元素的值置为pom

    <packaging>pom</packaging>
    
  3. 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:

file

删除无用的2目录.idea和src

file

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:

file

点击File->New->Module,准备创建模块,如下图:

file

选中Maven,如下图:

file

点击Next,这个页面需要注意了,默认如下图:

file

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:

file

file

变成了下面这样:

file

输入构件信息,如下图:

file

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

file

点击Finish完成创建操作,如下图:

file

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:

file

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:\code\IdeaProjects\javacode2018-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:\code\IdeaProjects\javacode2018-parent>cd javacode2018-pc

D:\code\IdeaProjects\javacode2018-parent\javacode2018-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.xmlparent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:\code\IdeaProjects\javacode2018-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:\code\IdeaProjects\javacode2018-parent>cd javacode2018-pc

D:\code\IdeaProjects\javacode2018-parent\javacode2018-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:\code\IdeaProjects\javacode2018-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:\code\IdeaProjects\javacode2018-parent>cd javacode2018-pc

D:\code\IdeaProjects\javacode2018-parent\javacode2018-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:

file

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:

file

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>

注意上面有两个关键元素:type的值必须是pom,scope元素的值必须是import

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:

file

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。

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

D:\code\IdeaProjects\javacode2018-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:\code\IdeaProjects\javacode2018-pom-import\src\test\resources
[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:\code\IdeaProjects\javacode2018-pom-import\target\javacode2018-pom-import-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pom-import ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-pom-import\target\javacode2018-pom-import-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pom-import\1.0-SNAPSHOT\javacode2018-pom-import-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-pom-import\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pom-import\1.0-SNAPSHOT\javacode2018-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.xmldependencyManagement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.xmlproject->dependencies元素中加入下面配置:

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

看一下效果:

file

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:

file

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

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-pluginjar-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:\code\IdeaProjects\javacode2018-parent\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-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:

file

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:\code\IdeaProjects\javacode2018-parent\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-source-plugin:3.2.0:jar-no-fork (attach-source) @ javacode2018-pc ---
[INFO] Building jar: D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT-sources.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.pom
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT-sources.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT-sources.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-pc ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.pom
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT-sources.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-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:helpjar-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:\code\IdeaProjects\javacode2018-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:\code\IdeaProjects\javacode2018-parent\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-parent\1.0-SNAPSHOT\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-pc-1.0-SNAPSHOT.pom
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-pc\target\javacode2018-pc-1.0-SNAPSHOT-sources.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-pc\1.0-SNAPSHOT\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-h5\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-h5\target\javacode2018-h5-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-h5 ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-h5\target\javacode2018-h5-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-h5\1.0-SNAPSHOT\javacode2018-h5-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-h5\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-h5\1.0-SNAPSHOT\javacode2018-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:\code\IdeaProjects\javacode2018-parent\javacode2018-api\src\test\resources
[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:\code\IdeaProjects\javacode2018-parent\javacode2018-api\target\javacode2018-api-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ javacode2018-api ---
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-api\target\javacode2018-api-1.0-SNAPSHOT.jar to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-api\1.0-SNAPSHOT\javacode2018-api-1.0-SNAPSHOT.jar
[INFO] Installing D:\code\IdeaProjects\javacode2018-parent\javacode2018-api\pom.xml to C:\Users\Think\.m2\repository\com\javacode2018\javacode2018-api\1.0-SNAPSHOT\javacode2018-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:\code\IdeaProjects\maven-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:\code\IdeaProjects\maven-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:\code\IdeaProjects\maven-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-plugintest目标。

我们看看这个目标详细参数,只列出部分信息,如下:

D:\code\IdeaProjects\maven-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

  1. 需要掌握聚合的使用
  2. 掌握继承的使用
  3. 掌握单继承问题解决方案
  4. 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!

Maven系列目录

  1. Maven系列:第1篇:Maven未出世前,我们那些痛苦的经历!
  2. Maven系列第2篇:安装、配置、mvn运行过程详解
  3. Maven系列第3篇:详解maven解决依赖问题
  4. Maven系列第4篇:仓库详解
  5. Maven系列第5篇:私服详解
  6. Maven系列第6篇:生命周期和插件详解,高手必备!

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