用Maven跑Java main的3種方法
概述
Maven exec plugin可以使我們執行自己工程的Java類的main方法，並在classpath裡自動包含工程的dependencies。本文用示例程式碼展示了使用maven exec plugin來執行java main方法的3種方法。
1) 在命令列（Command line）執行
用這種方式執行的話，並沒有在某個maven phase中，所以你首先需要compile（編譯）一下程式碼。
請記住exec:java不會自動編譯程式碼，需要先編譯才行。
mvn compile編譯完成後，用以下命令執行java main方法
不帶引數跑：
mvn exec 帶引數跑：
mvn exec:java -Dexec.mainClass="com.vineetmanohar.module.Main" -Dexec.args="arg0 arg1 arg2"在classpath裡用runtime依賴
mvn exec:java -Dexec.mainClass="com.vineetmanohar.module.Main" -Dexec.classpathScope=runtime2) 在pom.xml檔案的某個phase裡執行
也可以在maven的某個phase裡執行main方法。比如，作為test phase的一部分執行CodeGenerator.main()方法
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.1.1</version>
<executions 用以上配置執行exec plugin，執行相應的phase就行了。
mvn test3) 在pom.xml檔案的某個profile執行
也可以用不同的profile執行main方法。只要用<profile>標籤包裹住以上配置就行。
<profiles>
<profile>
<id>code-generator</id>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.1.1</version>
<executions>
<execution>
<phase>test</phase>
<goals>
<goal>java</goal>
</goals>
<configuration>
<mainClass>com.vineetmanohar.module.CodeGenerator</mainClass>
<arguments>
<argument>arg0</argument>
<argument>arg1</argument>
</arguments>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</profile>
</profiles>呼叫以上profile，執行以下命令就行：
mvn test -Pcode-generator高階選項
你可以通過以下命令來檢視所有引數的列表：
mvn exec:help -Ddetail=true -Dgoal=java arguments (exec.arguments)
The class arguments.(類引數)
classpathScope (exec.classpathScope, Default: compile)
Defines the scope of the classpath passed to the plugin. Set to
compile, test, runtime or system depending on your needs
定義傳遞給plugin的classpath的scope。根據需要設定為 compile, test, runtime 或system。
cleanupDaemonThreads (exec.cleanupDaemonThreads)
Wether to interrupt/join and possibly stop the daemon threads upon
quitting. If this is false, maven does nothing about the daemon threads.
When maven has no more work to do, the VM will normally terminate any
remaining daemon threads.
In certain cases (in particular if maven is embedded), you might need to
keep this enabled to make sure threads are properly cleaned up to ensure
they don’t interfere with subsequent activity. In that case, see
daemonThreadJoinTimeout and stopUnresponsiveDaemonThreads for further
tuning.
commandlineArgs (exec.args)
Arguments for the executed program
daemonThreadJoinTimeout (exec.daemonThreadJoinTimeout, Default: 15000)
This defines the number of milliseconds to wait for daemon threads to quit
following their interruption. This is only taken into account if
cleanupDaemonThreads is true. A value <=0 means to not timeout (i.e. wait
indefinitely for threads to finish). Following a timeout, a warning will
be logged. Note: properly coded threads should terminate upon interruption
but some threads may prove problematic: as the VM does interrupt daemon
threads, some code may not have been written to handle interruption
properly. For example java.util.Timer is known to not handle interruptions
in JDK <= 1.6. So it is not possible for us to infinitely wait by default
otherwise maven could hang. A sensible default value has been chosen, but
this default value may change in the future based on user feedback.
executableDependency
If provided the ExecutableDependency identifies which of the plugin
dependencies contains the executable class. This will have the affect of
only including plugin dependencies required by the identified
ExecutableDependency.
If includeProjectDependencies is set to true, all of the project
dependencies will be included on the executable’s classpath. Whether a
particular project dependency is a dependency of the identified
ExecutableDependency will be irrelevant to its inclusion in the classpath.
includePluginDependencies (exec.includePluginDependencies, Default: false)
Indicates if this plugin’s dependencies should be used when executing the
main class. This is useful when project dependencies are not appropriate. Using
only the plugin dependencies can be particularly useful when the project is not
a java project. For example a mvn project using the csharp plugins only expects
to see dotnet libraries as dependencies.
includeProjectDependencies (exec.includeProjectDependencies, Default: true)
Indicates if the project dependencies should be used when executing the
main class.
mainClass (exec.mainClass)
The main class to execute.
sourceRoot (sourceRoot)
This folder is added to the list of those folders containing source to be
compiled. Use this if your plugin generates source code.
stopUnresponsiveDaemonThreads (exec.stopUnresponsiveDaemonThreads)
Wether to call Thread.stop() following a timing out of waiting for an
interrupted thread to finish. This is only taken into account if
cleanupDaemonThreads is true and the daemonThreadJoinTimeout threshold has
been reached for an uncooperative thread. If this is false, or if
Thread.stop() fails to get the thread to stop, then a warning is logged
and Maven will continue on while the affected threads (and related objects
in memory) linger on. Consider setting this to true if you are invoking
problematic code that you can’t fix. An example is Timer which doesn’t
respond to interruption. To have Timer fixed, vote for this bug.
systemProperties
A list of system properties to be passed. Note: as the execution is not
forked, some system properties required by the JVM cannot be passed here.
Use MAVEN_OPTS or the exec:exec instead. See the user guide for more
information.
testSourceRoot (testSourceRoot)
This folder is added to the list of those folders containing source to be
compiled for testing. Use this if your plugin generates test source code.
問題和錯誤
為什麼在給main方法指定arguments時遇到以下錯誤呢？
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Failed to configure plugin parameters for: org.codehaus.mojo:exec-maven-plugin:1.1.1
on the command line, specify: '-Dexec.arguments=VALUE'
Cause: Cannot assign configuration entry 'arguments' to 'class [Ljava.lang.String;' from '${exec.arguments}',
which is of type class java.lang.String
[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.apache.maven.lifecycle.LifecycleExecutionException: Error configuring: org.codehaus.mojo:exec-maven-plugin.
Reason: Unable to parse the created DOM for plugin configuration
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:588)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:513)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:483)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:331)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:292)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:142)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:336)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:129)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:301) 解決辦法：
exec.arguments在exec plugin的1.1版本之前使用，它不支援命令列String到String[] array的轉換
- 如果可以，升級該外掛到1.1或更高，使用exec.args而不是exec.arguments
- 如果你不能升級外掛，你依然可以通過profile和在pom檔案裡使用多個
<argument>便籤來使用命令列引數。（If you can’t upgrade the plugin version, you can still use command line arguments with a profile and use multiple tags associated in the pom.xml）