3.Maven Enforcer plugin标签详解 - 王朝网络宽屏版

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.xml中配置插件。

<?xml version="1.0" encoding="UTF-8"?><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. Thisapplicationrequires 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 variablerequireFilesDontExist - 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：

<?xml version="1.0" encoding="UTF-8"?><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><searchTransitive>true</searchTransitive><excludes>

<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>...</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。

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