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19) maven 项目结构：聚集
Project Aggregation [,æɡr?‘ɡe???n]
https://maven.apache.org/guides/introduction/introduction-to-the-pom.html
https://maven.apache.org/guides/mini/guide-multiple-modules.html
模块式开发（将所有模块聚合在一个父pom）
使用一个父pom，管理各个模块，控制模块间依赖关系和构建顺序
开始一个简单的demo来理解这个结构
1.创建一个父pom（Maven Project）
<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>cn.zno</groupId> <artifactId>app-pom</artifactId> <version>1.0</version> <packaging>pom</packaging></project>
2.创建一个jar模块（Maven Module）
右键 app-pom
new Maven Module
<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>cn.zno</groupId> <artifactId>app-pom</artifactId> <version>1.0</version> </parent> <artifactId>app-jar</artifactId></project>
3.创建一个war模块
<?xml version="1.0"?><project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>cn.zno</groupId> <artifactId>app-pom</artifactId> <version>1.0</version> </parent> <artifactId>app-war</artifactId> <packaging>war</packaging> <name>app-war Maven Webapp</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> </dependencies> <build> <finalName>app-war</finalName> </build></project>
现在父pom自动修改为：
<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>cn.zno</groupId> <artifactId>app-pom</artifactId> <version>1.0</version> <packaging>pom</packaging> <modules> <module>app-jar</module> <module>app-war</module> </modules></project>
现在install app-pom
右键app-pom ，Run As ，Maven install
[INFO] Scanning for projects...[INFO] ------------------------------------------------------------------------[INFO] Reactor Build Order:[INFO] [INFO] app-pom[INFO] app-jar[INFO] app-war Maven Webapp[INFO] [INFO] ------------------------------------------------------------------------[INFO] Building app-pom 1.0[INFO] ------------------------------------------------------------------------[INFO] [INFO] --- maven-install-plugin:2.4:install (default-install) @ app-pom ---[INFO] Installing F:\e\workspacetest\app-pom\pom.xml to C:\Users\wl\.m2\repository\cn\zno\app-pom\1.0\app-pom-1.0.pom[INFO] [INFO] ------------------------------------------------------------------------[INFO] Building app-jar 1.0[INFO] ------------------------------------------------------------------------[INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ app-jar ---[WARNING] Using platform encoding (Cp1252 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) @ app-jar ---[INFO] Nothing to compile - all classes are up to date[INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ app-jar ---[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent![INFO] Copying 0 resource[INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ app-jar ---[INFO] Nothing to compile - all classes are up to date[INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ app-jar ---[INFO] [INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ app-jar ---[INFO] Building jar: F:\e\workspacetest\app-pom\app-jar\target\app-jar-1.0.jar[INFO] [INFO] --- maven-install-plugin:2.4:install (default-install) @ app-jar ---[INFO] Installing F:\e\workspacetest\app-pom\app-jar\target\app-jar-1.0.jar to C:\Users\wl\.m2\repository\cn\zno\app-jar\1.0\app-jar-1.0.jar[INFO] Installing F:\e\workspacetest\app-pom\app-jar\pom.xml to C:\Users\wl\.m2\repository\cn\zno\app-jar\1.0\app-jar-1.0.pom[INFO] [INFO] ------------------------------------------------------------------------[INFO] Building app-war Maven Webapp 1.0[INFO] ------------------------------------------------------------------------[INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ app-war ---[WARNING] Using platform encoding (Cp1252 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) @ app-war ---[INFO] No sources to compile[INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ app-war ---[WARNING] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent![INFO] skip non existing resourceDirectory F:\e\workspacetest\app-pom\app-war\src\test\resources[INFO] [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ app-war ---[INFO] No sources to compile[INFO] [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ app-war ---[INFO] [INFO] --- maven-war-plugin:2.2:war (default-war) @ app-war ---[INFO] Packaging webapp[INFO] Assembling webapp [app-war] in [F:\e\workspacetest\app-pom\app-war\target\app-war][INFO] Processing war project[INFO] Copying webapp resources [F:\e\workspacetest\app-pom\app-war\src\main\webapp][INFO] Webapp assembled in [36 msecs][INFO] Building war: F:\e\workspacetest\app-pom\app-war\target\app-war.war[INFO] WEB-INF\web.xml already added, skipping[INFO] [INFO] --- maven-install-plugin:2.4:install (default-install) @ app-war ---[INFO] Installing F:\e\workspacetest\app-pom\app-war\target\app-war.war to C:\Users\wl\.m2\repository\cn\zno\app-war\1.0\app-war-1.0.war[INFO] Installing F:\e\workspacetest\app-pom\app-war\pom.xml to C:\Users\wl\.m2\repository\cn\zno\app-war\1.0\app-war-1.0.pom[INFO] ------------------------------------------------------------------------[INFO] Reactor Summary:[INFO] [INFO] app-pom ............................................ SUCCESS [ 0.674 s][INFO] app-jar ............................................ SUCCESS [ 2.903 s][INFO] app-war Maven Webapp ............................... SUCCESS [ 0.759 s][INFO] ------------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] ------------------------------------------------------------------------[INFO] Total time: 4.483 s[INFO] Finished at: 2016-09-07T15:11:51+08:00[INFO] Final Memory: 13M/111M[INFO] ------------------------------------------------------------------------
做了这几件事：
install 了一个pom文件
install 了一个 jar 文件
install 了一个 war 文件
构建顺序引用官网的话：
The following relationships are honoured when sorting projects:
- a project dependency on another module in the build
- a plugin declaration where the plugin is another modules in the build
- a plugin dependency on another module in the build
- a build extension declaration on another module in the build
- the order declared in the <modules> element (if no other rule applies)
因为app-war 和 app-jar 没有依赖关系，所以构建顺序是用的最后一个规则（modules 声明顺序）
为何模块化开发
- 分工明确代码复用
- SOA模块便于分布式
- 保护源码权限控制
- 局部构建节省时间
1.开发过程中可能遇到多个项目，里面的dao ，servie， util 重复使用，形成代码到处复制粘贴。等到想修改某处逻辑时傻眼了，因为要改N处。无谓的加大了开发成本和维护成本。
2.并发访问量提升之后考虑的SOA，如果最初设计时没有服务模块化，改动成本巨大。
3.版本控制软件svn 、git，如果代码全在一处，虽然只分配一个小任务只涉及到小部分代码，但全部的代码都要被下载下来。
4. 只修改了一个小功能没想到需要整体构建一下子，慢慢慢。
19) maven 项目结构：聚集
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