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[Java教程]学习 Maven之Maven Enforcer plugin


1.Maven Enforcer plugin是什么鬼?

在说这个插件是什么前我们先思考这么一个问题:当我们开发人员进入项目组进行开发前,要准备开发环境,而领导总是会强调工具的统一,编译环境的统一。比如要求所有开发人员使用JDK1.8进行开发。

开发人员接下来就是去下载指定版本的JDK,然后开始开发。但是如果开发人员的机器配置比较多,有好几个版本的JDK,而他虽然下载了JDK1.8,但是忘记配置环境变量,很有可能他用了JDK1.6进行的编译。

问题有了,该如何解决? Maven Enforcer plugin就是来解决这类问题。Enforcer可以在项目validate时,对项目环境进行检查。

 

2.Maven Enforcer plugin怎么用?

Enforcer配置后默认会在validate后执行enforcer:enforce,然后对项目环境进行检查。拿上面对JDK的校验为例,我们在pom.

<??><project>...  <build>    <plugins>      <plugin>        <artifactId>maven-enforcer-plugin</artifactId>        <version>1.4.1</version>        <executions>          <execution>            <id>default-cli</id>            <goals>              <goal>enforce</goal>            </goals>            <phase>validate</phase>            <configuration>              <rules>                <requireJavaVersion>                  <message>                    <![CDATA[You are running an older version of Java. This application requires at least JDK ${java.version}.]]>                  </message>                  <version>[${java.version}.0,)</version>                </requireJavaVersion>              </rules>            </configuration>          </execution>        </executions>      </plugin>    </plugins>  </build>  <properties>    <java.version>1.8</java.version>  </properties> </project>

我本地配置没有JDK1.8,按照我的期望,执行maven命令时应该会失败。让我们来执行命令 mvn validate 会打出如下日志告知我们JDK版本过低。

qyfmac$ mvn validate[INFO] Scanning for projects...[INFO] ------------------------------------------------------------------------[INFO] Reactor Build Order:[INFO] [INFO] AppFuse Modular Application[INFO] AppFuse Modular Application - Core[INFO] AppFuse Modular Application - Web (Spring MVC)[INFO]                                     [INFO] ------------------------------------------------------------------------[INFO] Building AppFuse Modular Application 1.0-SNAPSHOT[INFO] ------------------------------------------------------------------------[INFO] [INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-versions) @ stock ---[WARNING] Rule 1: org.apache.maven.plugins.enforcer.RequireJavaVersion failed with message:You are running an older version of Java. This application requires at least JDK 1.8.[INFO] ------------------------------------------------------------------------[INFO] Reactor Summary:[INFO] [INFO] AppFuse Modular Application ........................ FAILURE [ 0.987 s][INFO] AppFuse Modular Application - Core ................. SKIPPED[INFO] AppFuse Modular Application - Web (Spring MVC) ..... SKIPPED[INFO] ------------------------------------------------------------------------[INFO] BUILD FAILURE[INFO] ------------------------------------------------------------------------[INFO] Total time: 1.886 s[INFO] Finished at: 2015-09-22T15:37:04+08:00[INFO] Final Memory: 16M/156M[INFO] ------------------------------------------------------------------------[ERROR] Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce (enforce-versions) on project stock: Some Enforcer rules have failed. Look above for specific messages explaining why the rule failed. -> [Help 1][ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.[ERROR] Re-run Maven using the -X switch to enable full debug logging.[ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles:[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

其实执行命令 mvn enforcer:enforce 也可以达到上面的效果。区别就是validate是maven全局命令,enforcer:enforce是只执行这个插件的命令。

这里要注意一点,执行enforcer:enforce时,id必须是default-cli(具体原因请参阅:http://stackoverflow.com/questions/24827194/maven-enforcer-plugin-missing-or-invalid-rules),否则会报

The parameters 'rules' for goal org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce are missing or invalid

 

3.Maven Enforcer plugin标签详解

现在对这个插件的配置讲解一下。

<plugin><artifactId>maven-enforcer-plugin</artifactId><version>1.4.1</version><executions> <execution>  <id>default-cli</id>     --一个执行实例的id   <goals>    <goal>enforce</goal>   --执行的命令   </goals>   <phase>validate</phase>  --执行的阶段   <configuration>    <rules>         --规则     <requireJavaVersion>  --JDK的版本      <message>      --失败后提示消息       <![CDATA[You are running an older version of Java. This application requires at least JDK ${java.version}.]]>       </message>       <version>[${java.version}.0,)</version>  --JDK版本规则      </requireJavaVersion>     </rules>    </configuration>  </execution> </executions></plugin>    

 

Enforcer的rules除了控制JDK版本,还有很多其他规则,甚至可以通过它的接口自定义。

  • alwaysFail - Always fail... used to test plugin configuration.
  • alwaysPass - Always passes... used to test plugin configuration.
  • banDistributionManagement - enforces that project doesn't have distributionManagement.
  • bannedDependencies - enforces that excluded dependencies aren't included.
  • bannedPlugins - enforces that specific plugins aren't included in the build.
  • bannedRepositories - enforces to not include banned repositories.
  • banTransitiveDependencies - enforces that project doesn't have transitive dependencies.
  • dependencyConvergence - ensure all dependencies converge to the same version.
  • evaluateBeanshell - evaluates a beanshell script.
  • reactorModuleConvergence - enforces that a multi module build follows best practice.
  • requireActiveProfile - enforces one or more active profiles.
  • requireEnvironmentVariable - enforces the existence of an environment variable
  • requireFilesDontExist - enforces that the list of files does not exist.
  • requireFilesExist - enforces that the list of files does exist.
  • requireFilesSize - enforces that the list of files exists and is within a certain size range.
  • requireJavaVersion - enforces the JDK version.
  • requireMavenVersion - enforces the Maven version.
  • requireNoRepositories - enforces to not include repositories.
  • requireOS - enforces the OS / CPU Architecture.
  • requirePluginVersions - enforces that all plugins have a specified version.
  • requirePrerequisite - enforces that prerequisites have been specified.
  • requireProperty - enforces the existence and values of properties.
  • requireReleaseDeps - enforces that no snapshots are included as dependencies.
  • requireReleaseVersion - enforces that the artifact is not a snapshot.
  • requireSameVersions - enforces that specific dependencies and/or plugins have the same version.
  • requireUpperBoundDeps - ensures that every (transitive) dependency is resolved to it's specified version or higher.

You may also create and inject your own custom rules by following the maven-enforcer-rule-api instructions.

 

我们再写一个例子。比如除了需要限制JDK外,我们还要限定maven版本,项目不得包含TestNG依赖,操作系统必须是mac os x 64位,项目版本号在执行install时必须是正式版本。

直接上代码:

<??><project>...  <build>    <plugins>      <plugin>        <artifactId>maven-enforcer-plugin</artifactId>        <version>1.4.1</version>        <executions>          <execution>            <id>default-cli</id>            <goals>              <goal>display-info</goal>              <goal>enforce</goal>            </goals>            <phase>validate</phase>            <configuration>              <rules>                <requireMavenVersion>                  <message>                    <![CDATA[You are running an older version of Maven. This application requires at least Maven ${maven.version}.]]>                  </message>                  <version>[${maven.version},)</version>                </requireMavenVersion>                <requireJavaVersion>                  <message>                    <![CDATA[You are running an older version of Java. This application requires at least JDK ${java.version}.]]>                  </message>                  <version>[${java.version}.0,)</version>                </requireJavaVersion>                <bannedDependencies>                  <!--是否检查传递性依赖(间接依赖)-->                  <searchTransitive>true</searchTransitive>                  <excludes>                    <!--groupId[:artifactId][:version][:type][:scope][:classifier]--> 
<exclude>org.testng:testng</exclude> </excludes> <message>don't use TestNG,must use JUnit</message> </bannedDependencies> <requireOS> <name>mac os x</name> <family>mac</family> <arch>x86_64</arch> <version>10.10.3</version> </requireOS> <requireProperty> <property>project.version</property> <message>"Project version must be specified."</message> <regex>.*(\d|-SNAPSHOT)$</regex> <regexMessage>"Project version must end in a number or -SNAPSHOT."</regexMessage> </requireProperty> </rules> </configuration> </execution> <execution> <id>enforce-install</id> <goals> <goal>enforce</goal> </goals> <phase>install</phase> <configuration> <rules> <requireProperty> <property>project.version</property> <message>"Project version must be specified."</message> <regex>.*(\d)$</regex> <regexMessage>"Project version must end in a number."</regexMessage> </requireProperty> </rules> </configuration> </execution> </executions> </plugin> </plugins> </build> <dependencies> ... <!--测试放开--> <!--<dependency>--> <!--<groupId>org.testng</groupId>--> <!--<artifactId>testng</artifactId>--> <!--<version>6.1.1</version>--> <!--<scope>test</scope>--> <!--</dependency>--> </dependencies> <properties> <java.version>1.7</java.version> <maven.version>3.3.3</maven.version> </properties></project>

这里要说一下requireOS了,不支持表达式,必须准确的写一个版本号,个人认为这个不好,不过可以把version注释掉,不校验操作系统的版本。

如果某些情况下不检查环境,可以在maven命令上加一个 -Denforcer.skip=true 来跳过enforcer插件执行。
例如:mvn clean validate -Denforcer.skip=true

 

更多神奇的配置方式还请参阅官方网站 :http://maven.apache.org/enforcer/maven-enforcer-plugin/index.html。