前情回顧
在上一章節中,通過三個模塊的項目開發,講解了Maven依賴管理的特性,從而對Maven依賴的表現,範圍等有着一定的認識,但每次對一個模塊進行更改,都要將對應模塊進行test或者package或者install的操作後,使用到該模塊的項目纔可以使用,這樣的操作有些繁瑣,如果有過多的模塊,那將需要執行多次的操作,還有,在每個模塊pom.xml文件中,存在很多之前模塊相同的依賴包,並且以後開發時候還會有很多相同的常量。
問題引出
能不能執行一次命令就可以完成對每個模塊的操作?(Maven的聚合)
能不能不要在每個模塊中都要定義相同的依賴包或者重複的元素呢?(Maven的繼承)
聚合和繼承的實現
在實現過程中,將繼續使用上一個章節構建的項目模塊,並在上進行更改,如果沒有項目概念的,可以參考上一章節的講解,構建相應的項目。
聚合繼承的操作只要在項目模塊的目錄中創建實現的pom.xml文件,然後在pom.xml文件中定義相應的操作即可,如下圖所示
圖1
但在這裏我們可以通過Eclipse構建pom.xml文件(可以同時進行聚合和繼承的操作),可以通過以下步驟
圖2
圖3
圖4
然後生成pom.xml文件
圖5
此時聚合的實現,只要在pom.xml中添加聚合的模塊即可,實現的操作如下所示:
<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.steven.user</groupId>
<artifactId>user-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>../user-core</module>
<module>../user-log</module>
<module>../user-service</module>
</modules>
</project>
注意:
這裏的<module>模塊中../是指代上一級目錄,因爲在Eclipse中需要指向上一級纔可以引入相應的模塊。
這時候,對parent模塊執行clean操作,會發現其包含的每個模塊都已經執行了操作,
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO]
[INFO] user-core
[INFO] user-log
[INFO] user-service
[INFO] user-parent
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building user-core 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ user-core ---
[INFO] Deleting E:\Workspaces\STSWorkspace\user-core\target
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building user-log 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ user-log ---
[INFO] Deleting E:\Workspaces\STSWorkspace\user-log\target
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building user-service 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ user-service ---
[INFO] Deleting E:\Workspaces\STSWorkspace\user-service\target
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building user-parent 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ user-parent ---
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] user-core ......................................... SUCCESS [0.255s]
[INFO] user-log .......................................... SUCCESS [0.014s]
[INFO] user-service ...................................... SUCCESS [0.015s]
[INFO] user-parent ....................................... SUCCESS [0.002s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.500s
[INFO] Finished at: Mon Feb 17 21:21:50 CST 2014
[INFO] Final Memory: 4M/15M
[INFO] ------------------------------------------------------------------------
下面進行繼承的操作,繼承的操作在這裏主要對依賴和常量進行配置,配置後的pom文件依次是
user-parent中pom.xml
<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.steven.user</groupId>
<artifactId>user-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>../user-core</module>
<module>../user-log</module>
<module>../user-service</module>
</modules>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.14</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.1.1.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.8</version>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.5</version>
</dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>user-core</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>user-log</artifactId>
<version>${project.version}</version>
<exclusions>
<exclusion>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
</dependencyManagement>
</project>
user-core中pom.xml
<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.steven.user</groupId>
<artifactId>user-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../user-parent/pom.xml</relativePath>
</parent>
<artifactId>user-core</artifactId>
<packaging>jar</packaging>
<name>user-core</name>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
</dependencies>
</project>
user-log中pom.xml
<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.steven.user</groupId>
<artifactId>user-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../user-parent/pom.xml</relativePath>
</parent>
<artifactId>user-log</artifactId>
<packaging>jar</packaging>
<name>user-log</name>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
</dependency>
</dependencies>
</project>
user-service中pom.xml
<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.steven.user</groupId>
<artifactId>user-parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../user-parent/pom.xml</relativePath>
</parent>
<artifactId>user-service</artifactId>
<packaging>jar</packaging>
<name>user-service</name>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>user-core</artifactId>
</dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>user-log</artifactId>
</dependency>
</dependencies>
</project>
此時即可完成繼承的操作,會發現user-core,user-log,user-service中版本號,依賴範圍,排除依賴都不需要寫了,只要都寫在父文件中就可以了,這樣就減少了很多重複代碼的編寫了。
總結
此時就可以通過父類user-parent執行聚合繼承操作後,對其他模塊進行統一管理,這裏有幾個提示點:
1、通過聚合就可以共同操作,通過繼承就可以解決jar衝突,排除依賴一樣可以寫在父文件中,
2、在Eclipse中進行對模塊依賴的控制,可以先將一個模塊的所有依賴放到父文件的<dependencyManagement>節點下,然後在該模塊中Eclipse會有重複的提示,刪除重複行即可,然後在其他模塊中先對重複行進行刪除,對父文件中沒有的依賴進行拷貝。
在此預祝大家學習愉快!有任何錯誤或者問題可以提出,在此不勝感激!