欢迎您光临本小站。希望您在这里可以找到自己想要的信息。。。

学习Maven之Maven Enforcer Plugin

java water 564℃ 0评论

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. 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。

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>
                                    <!--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。 

我们会经常碰到这样的问题,在pom中引入了一个jar,里面默认依赖了其他的jar包。jar包一多的时候,我们很难确认哪些jar是我们需要的,哪些jar是冲突的。此时会出现很多莫名其妙的问题,什么类找不到啦,方法找不到啦,这种可能的原因就是jar的版本不是我们所设想的版本,但是我们也不知道低版本的jar是从哪个maven里面引用的。此时我们的maven-enforcer-plugin就可以登场了。

<project>
  ...
  <build>
    <plugins>
      ...
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>1.4.1</version>
        <executions>
          <execution>
            <id>enforce</id>
            <configuration>
              <rules>
                <dependencyConvergence/>
              </rules>
            </configuration>
            <goals>
              <goal>enforce</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      ...
    </plugins>
  </build>
  ...
</project>

在进行mvn clean package的时候,会在console中打印出来冲突的jar版本和其父pom,如下:

Dependency convergence error for org.slf4j:slf4j-api1.6.1 paths to dependency are:
 
[ERROR]
Dependency convergence error for org.slf4j:slf4j-api:1.6.1 paths to dependency are:
+-org.myorg:my-project:1.0.0-SNAPSHOT
  +-org.slf4j:slf4j-jdk14:1.6.1
    +-org.slf4j:slf4j-api:1.6.1
and
+-org.myorg:my-project:1.0.0-SNAPSHOT
  +-org.slf4j:slf4j-nop:1.6.0
    +-org.slf4j:slf4j-api:1.6.0

这个时候,我们看一眼就知道应该把那个dependency中的哪个jar进行exclude。

这是一个小技巧,不过很管用。

转载请注明:学时网 » 学习Maven之Maven Enforcer Plugin

喜欢 (0)or分享 (0)

您必须 登录 才能发表评论!