To simplify the build processes of a project---Maven

Maven概述：

为项目的构建提供了一个标准的方案，使得项目组成的定义更加清晰，更容易地实现项目的构建。使得jar在多个项目里面的共享。

创建Maven项目：

使用命令行创建Maven项目：

mvn archetype:generate
-DgroupId=com.mycompany.app
-DartifactId=my-app
-DarchetypeArtifactId=maven-archetype-quickstart
-DarchetypeVersion=1.4 -DinteractiveMode=false

使用IDEA创建Maven项目：

两种方式中相关属性说明：

groupId：一般是公司或者组织域名的倒序。
artifactId：项目名称（如果是多个工程构成的项目，这里就指工程名）。
archetypeArtifactId：Maven提供的archetype（可以通俗地理解为模板，Maven project templating toolkit）。
(Version)archetypeVersion：该项目（工程）的版本号。

POM（项目对象模型，pom.xml文件）

<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.mycompany.app</groupId>
  <artifactId>my-app</artifactId>
  <version>1.0-SNAPSHOT</version>
 
  <properties>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>
 
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

Is the core of a project's configuration in Maven.
项目中用到的其他Jar包通过dependency的方式引入。
以dependency方式引入的依赖，所依赖的jar也会自动引入。
自己写的代码可以通过Packge打包，下次在其他项目引入即可。
依赖先找本地Maven仓库，没有就去远程中央仓库找。

一个POM文件至少包含以下内容:

project root.
modelVersion - should be set to 4.0.0.
groupId - the id of the project's group.
artifactId - the id of the artifact (project)
version - the version of the artifact under the specified group

构建生命周期

Maven的构建生命周期是由阶段组成(阶段又由插件目标（Plugin Goals）组成)，默认的构建生命周期包含如下生命周期：

validate - validate the project is correct and all necessary information is available.
compile - compile the source code of the project.
test - test the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed.
package - take the compiled code and package it in its distributable format, such as a JAR.
verify - run any checks on results of integration tests to ensure quality criteria are met.
install - install the package into the local repository, for use as a dependency in other projects locally.
deploy - done in the build environment, copies the final package to the remote repository for sharing with other developers and projects.

注意：阶段是由上而下依次执行，可通过命令行跳过一些阶段，如：mvn package -Dmaven.test.skip=true

Super POM:所有的POM文件都继承自SuperPOM，除非有明确的设置。

<project>
  <modelVersion>4.0.0</modelVersion>
 
  <repositories>
    <repository>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
    </repository>
  </repositories>
 
  <pluginRepositories>
    <pluginRepository>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
      <layout>default</layout>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
    </pluginRepository>
  </pluginRepositories>
 
  <build>
    <directory>${project.basedir}/target</directory>
    <outputDirectory>${project.build.directory}/classes</outputDirectory>
    <finalName>${project.artifactId}-${project.version}</finalName>
    <testOutputDirectory>${project.build.directory}/test-classes</testOutputDirectory>
    <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
    <scriptSourceDirectory>${project.basedir}/src/main/scripts</scriptSourceDirectory>
    <testSourceDirectory>${project.basedir}/src/test/java</testSourceDirectory>
    <resources>
      <resource>
        <directory>${project.basedir}/src/main/resources</directory>
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>${project.basedir}/src/test/resources</directory>
      </testResource>
    </testResources>
    <pluginManagement>
      <!-- NOTE: These plugins will be removed from future versions of the super POM -->
      <!-- They are kept for the moment as they are very unlikely to conflict with lifecycle mappings (MNG-4453) -->
      <plugins>
        <plugin>
          <artifactId>maven-antrun-plugin</artifactId>
          <version>1.3</version>
        </plugin>
        <plugin>
          <artifactId>maven-assembly-plugin</artifactId>
          <version>2.2-beta-5</version>
        </plugin>
        <plugin>
          <artifactId>maven-dependency-plugin</artifactId>
          <version>2.8</version>
        </plugin>
        <plugin>
          <artifactId>maven-release-plugin</artifactId>
          <version>2.5.3</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
 
  <reporting>
    <outputDirectory>${project.build.directory}/site</outputDirectory>
  </reporting>
 
  <profiles>
    <!-- NOTE: The release profile will be removed from future versions of the super POM -->
    <profile>
      <id>release-profile</id>
 
      <activation>
        <property>
          <name>performRelease</name>
          <value>true</value>
        </property>
      </activation>
 
      <build>
        <plugins>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-source-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-sources</id>
                <goals>
                  <goal>jar-no-fork</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-javadoc-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-javadocs</id>
                <goals>
                  <goal>jar</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
          <plugin>
            <inherited>true</inherited>
            <artifactId>maven-deploy-plugin</artifactId>
            <configuration>
              <updateReleaseInfo>true</updateReleaseInfo>
            </configuration>
          </plugin>
        </plugins>
      </build>
    </profile>
  </profiles>

</project>

项目构建Maven