Maven浅窥二：复杂项目

基于前两篇《Maven浅窥一：基础》，已经可以成功地创建Maven项目了。

复杂项目的模块管理

复杂项目结构下，通常包括多个模块。而这多个模块必然有一些公共依赖。这时，可以将公共部分提出来以简化模块管理。以下是实现复杂项目管理的几种方式。

复杂项目的模块管理方式一

方式一：用根目录下的POM中维护公共依赖。

查看代码 https://github.com/alvachien/learning-notes/tree/master/maven-tutorial-2/maven-way-1

complex-project    
├──── pom.xml   
├──── module-a   
│     ├──── pom.xml   
│     └──── src    
├──── module-b   
│     ├──── pom.xml    
│     └──── src     
└──── module-c     
      ├──── pom.xml     
      └──── src     

根目录的pom.xml如下：

<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.alvachien.learning.maven-tutorial-2</groupId>
  <artifactId>maven-way-1</artifactId>
  <version>1.1.0-SNAPSHOT</version>
  <packaging>pom</packaging>

  <name>maven-tutorial-2</name>
  <url>http://maven.apache.org</url>
  
	<properties>
    <maven.compiler.release>15</maven.compiler.release>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.1</version>
        </plugin>
 			  <plugin>
				  <artifactId>maven-surefire-plugin</artifactId>
				  <version>2.22.2</version>
			  </plugin>
     </plugins>
    </pluginManagement>
  </build>    

	<dependencyManagement>
		<dependencies>
      <dependency>
        <groupId>org.junit</groupId>
        <artifactId>junit-bom</artifactId>
        <version>5.7.0</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

  <modules>
    <module>module-a</module>
  </modules>
</project>

而子目录，如module-a下的pom.xml如下：

<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>

  <parent>
    <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
    <artifactId>maven-way-1</artifactId>
    <version>1.1.0-SNAPSHOT</version>
    <relativePath>../</relativePath>
  </parent>

  <artifactId>module-a</artifactId>
  <packaging>jar</packaging>

  <name>module-a</name>
</project>

复杂项目的模块管理方式二

方式二：将放在一个公用目录，下例中，该公共目录是\parent\。

查看代码 https://github.com/alvachien/learning-notes/tree/master/maven-tutorial-2/maven-way-2

复杂项目结构下，通常包括多个模块。而这多个模块必然有一些公共依赖。这时，可以将公共部分提出来放在一个公用目录，下例中，该公共目录是\parent\。示例如下：

complex-project    
├──── pom.xml   
├──── parent   
│     └──── pom.xml   
├──── module-a   
│     ├──── pom.xml   
│     └──── src    
├──── module-b   
│     ├──── pom.xml    
│     └──── src     
└──── module-c     
      ├──── pom.xml     
      └──── src     

根目录下pom.xml如下：

<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.alvachien.learning.maven-tutorial-2</groupId>
  <artifactId>maven-way-2</artifactId>
  <version>1.2.0-SNAPSHOT</version>
  <packaging>pom</packaging>

  <url>http://maven.apache.org</url>
  <name>build</name>

  <modules>
    <module>parent</module>
    <module>module-a</module>
  </modules>
</project>

子目录parent下的pom.xml如下：

<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.alvachien.learning.maven-tutorial-2</groupId>
  <artifactId>parent</artifactId>
  <version>1.2.0-SNAPSHOT</version>
  <packaging>pom</packaging>

  <name>maven-tutorial</name>
  <url>http://maven.apache.org</url>
  
  <properties>
    <maven.compiler.release>15</maven.compiler.release>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.1</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>    

	<dependencyManagement>
		<dependencies>
      <dependency>
        <groupId>org.junit</groupId>
        <artifactId>junit-bom</artifactId>
        <version>5.7.0</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>
</project>

子目录下module-a的pom.xml如下：

<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>

    <parent>
      <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
      <artifactId>parent</artifactId>
      <version>1.2.0-SNAPSHOT</version>
      <relativePath>../parent</relativePath>
    </parent>

    <artifactId>module-a</artifactId>
    <packaging>jar</packaging>
    <name>module-a</name>
</project>

复杂项目的模块管理方式三

方式三，Bill of materials

官方文档见： 链接

代码 https://github.com/alvachien/learning-notes/tree/master/maven-tutorial-2/maven-way-3

complex-project    
├──── pom.xml   
└──── parent   
      ├──── pom.xml   
      ├──── module-a   
      │     ├──── pom.xml   
      │     └──── src    
      ├──── module-b   
      │     ├──── pom.xml    
      │     └──── src     
      └──── module-c     
            ├──── pom.xml     
            └──── src     

根目录下的pom.xml如下：

<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.alvachien.learning.maven-tutorial-2</groupId>
  <artifactId>bom</artifactId>
  <version>1.0.0</version>
  <packaging>pom</packaging>

  <properties>
    <module1Version>1.0.0</module1Version>
    <maven.compiler.release>15</maven.compiler.release>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>
 
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.1</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>    

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
        <artifactId>module-a</artifactId>
        <version>${module1Version}</version>
      </dependency>
    </dependencies>
  </dependencyManagement>
 
  <modules>
    <module>parent</module>
  </modules>
</project>

子目录parent下的pom.xml如下：

<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>
  <parent>
    <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
    <artifactId>bom</artifactId>
    <version>1.0.0</version>
    <relativePath>../pom.xml</relativePath>
  </parent>
 
  <artifactId>parent</artifactId>
  <version>1.0.0</version>
  <packaging>pom</packaging>
 
	<dependencyManagement>
		<dependencies>
      <dependency>
        <groupId>org.junit</groupId>
        <artifactId>junit-bom</artifactId>
        <version>5.7.0</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

  <modules>
    <module>module-a</module>
  </modules>
</project>

子目录module-a下pom.xml如下：

<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>
  <parent>
    <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
    <artifactId>parent</artifactId>
    <version>1.0.0</version>
    <relativePath>../pom.xml</relativePath>
  </parent>

  <artifactId>module-a</artifactId>
  <version>${module1Version}</version>
  <packaging>jar</packaging>
 
  <dependencies>
    <dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter</artifactId>
    </dependency>
  </dependencies>
</project>

如想要使用上面定义的library，则目标项目的pom.xml如下：

<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.consumer</groupId>
  <artifactId>use</artifactId>
  <version>1.0.0</version>
  <packaging>jar</packaging>
 
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
        <artifactId>bom</artifactId>
        <version>1.0.0</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.alvachien.learning.maven-tutorial-2</groupId>
      <artifactId>module-a</artifactId>
    </dependency>
  </dependencies>
</project>