java Spring boot 和 maven exec 插件问题
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Spring boot and maven exec plugin issue
提问by steady rain
I've created a bare-bone Maven project, completely empty except the pom.xml.
我创建了一个基本的 Maven 项目，除了pom.xml.
With this pom (note that parentelement is commented-out):
使用这个 pom（注意parent元素被注释掉）：
<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>springboot-test</groupId>
<artifactId>springboot-test</artifactId>
<version>1.0.0-SNAPSHOT</version>
<!-- <parent> -->
<!-- <groupId>org.springframework.boot</groupId> -->
<!-- <artifactId>spring-boot-starter-parent</artifactId> -->
<!-- <version>1.1.9.RELEASE</version> -->
<!-- </parent> -->
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.2</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
Sample run:
示例运行：
$ mvn exec:java -Dexec.mainClass=test
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building springboot-test 1.0.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.3.2:java (default-cli) @ springboot-test ---
[WARNING] Warning: killAfter is now deprecated. Do you need it ? Please comment on MEXEC-6.
[WARNING]
java.lang.ClassNotFoundException: test
at java.net.URLClassLoader.run(URLClassLoader.java:372)
at java.net.URLClassLoader.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.codehaus.mojo.exec.ExecJavaMojo.run(ExecJavaMojo.java:281)
at java.lang.Thread.run(Thread.java:745)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.480 s
[INFO] Finished at: 2014-12-05T13:45:34-05:00
[INFO] Final Memory: 8M/176M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.3.2:java (default-cli) on project springboot-test: An exception occured while executing the Java class. test -> [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
This is expected (there's no clas testin this project).
这是预期的（test此项目中没有类）。
Using this pom (i.e. just un-commenting parent):
使用这个 pom（即只是取消注释parent）：
<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>springboot-test</groupId>
<artifactId>springboot-test</artifactId>
<version>1.0.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.1.9.RELEASE</version>
</parent>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.2</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
Sample run:
示例运行：
$ mvn exec:java -Dexec.mainClass=test
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building springboot-test 1.0.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) > validate @ springboot-test >>>
[INFO]
[INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) < validate @ springboot-test <<<
[INFO]
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ springboot-test ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.550 s
[INFO] Finished at: 2014-12-05T13:45:27-05:00
[INFO] Final Memory: 12M/178M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project springboot-test: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java are missing or invalid -> [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/PluginParameterException
Same thing happens with exec-maven-plugin:1.3.2:
exec-maven-plugin:1.3.2 也会发生同样的事情：
$ mvn org.codehaus.mojo:exec-maven-plugin:1.3.2:java -Dexec.mainClass=test
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building springboot-test 1.0.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.3.2:java (default-cli) @ springboot-test ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.400 s
[INFO] Finished at: 2014-12-05T13:52:46-05:00
[INFO] Final Memory: 6M/157M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.3.2:java (default-cli) on project springboot-test: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.3.2:java are missing or invalid -> [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/PluginParameterException
Additional information:
附加信息：
$ java -version
java version "1.8.0_11"
Java(TM) SE Runtime Environment (build 1.8.0_11-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.11-b03, mixed mode)
$ mvn -v
Apache Maven 3.2.2 (45f7c06d68e745d05611f7fd14efb6594181933e; 2014-06-17T09:51:42-04:00)
Maven home: C:\dev\bin\apache-maven-3.2.2
Java version: 1.8.0_11, vendor: Oracle Corporation
Java home: C:\progra~1\java\jdk1.8.0_11\jre
Default locale: en_US, platform encoding: Cp1252
OS name: "windows 7", version: "6.1", arch: "amd64", family: "dos"
Questions:
问题：
- Why is this failing / how to fix?
- Why is this failing when
parentis added? How isexec-maven-plugininfluenced by this?
- 为什么会失败/如何解决？
- 为什么
parent添加时会失败？exec-maven-plugin受此影响如何？
(As a side note, I love the fact that Windows 7 belongs to faimly: "dos", I'm waiting for family: "cp/m" to be implemented for Windows 8.1)
（作为旁注，我喜欢 Windows 7 属于家庭的事实：“dos”，我正在等待家庭：“cp/m”为 Windows 8.1 实施）
回答by Mike R
Its because Spring-Boot is adding some extra maven configuration to your project. If you are using eclipse, there's a Tab called: 'Effective POM'.
这是因为 Spring-Boot 正在向您的项目添加一些额外的 Maven 配置。如果您使用的是 eclipse，则有一个名为“Effective POM”的选项卡。
From this tab you can see that it adds this snippet below:
从这个选项卡你可以看到它在下面添加了这个片段：
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<configuration>
<mainClass>${start-class}</mainClass>
</configuration>
</plugin>
So when you run it with spring-boot as parent, it looks for the value of ${start-class}, which resolves to empty unless you defined it, that's when you see the error about not having a value for the mainClassparameter.
因此，当您以 spring-boot 作为父级运行它时，它会查找 的值${start-class}，除非您定义它，否则该值解析为空，这时您会看到有关没有mainClass参数值的错误。
Add this to your project:
将此添加到您的项目中：
<properties>
<start-class>com.Test</start-class>
</properties>
Then run it: clean compile exec:java
然后运行它： clean compile exec:java
[INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ springboot-test --- **********test************** [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.388 s [INFO] Finished at: 2014-12-05T15:25:05-06:00 [INFO] Final Memory: 17M/231M [INFO] ------------------------------------------------------------------------
You can also provide the value for the start-classproperty on the command line, this works even if you didn't define it inside your pom file:
您还可以在start-class命令行上提供属性的值，即使您没有在 pom 文件中定义它，这也有效：
mvn exec:java -Dstart-class=com.Test
mvn exec:java -Dstart-class=com.Test
