WordCount示例在Eclipse中运行，但不在终端中运行

Question

I tried running first of the WordCount examples and it works in Eclipse (I have Windows 7 OS), but not in shell, using the command:

mvn compile exec:java -Dexec.mainClass=com.google.cloud.dataflow.examples.MinimalWordCount

I have installed Maven and configured JAVA_HOME and Path variables and so on, however, I'm not sure what I must have missed. This is the output:

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Tutorial 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ Tutorial ---
[WARNING] Using platform encoding (Cp1250 actually) to copy filtered resources,
i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory C:\Java\eclipse-jee-luna-SR2-win32-x8
6_64\eclipse\workspace\Tutorial\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.3:compile (default-compile) @ Tutorial --
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- exec-maven-plugin:1.4.0:java (default-cli) @ Tutorial ---
[WARNING]
java.lang.ClassNotFoundException: com.google.cloud.dataflow.examples.MinimalWord
Count
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:281)
    at java.lang.Thread.run(Thread.java:744)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.011 s
[INFO] Finished at: 2015-11-03T01:11:57+01:00
[INFO] Final Memory: 17M/178M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java 
(default-cli) on project Tutorial: An exception occured while executing the Java 
class. com.google.cloud.dataflow.examples.MinimalWordCount -> [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/MojoExecutionE
xception-

I am in the dark about how to proceed and would very much appreciate ideas of where to look next and other things to try.

Thanks!

Answer 1

You may have run into an issue with the documentation.

The command line you are using should work if you have cloned GoogleCloudPlatform/DataflowJavaSDK-examples . The mention of the particular repo to clone is way back in " getting started ", not at all obvious if you head straight to WordCount Example Pipeline .

But if you generated the project from the Cloud Dataflow Plugin for Eclipse (or via a Maven archetype ) then the examples are placed into your Java package. So instead of com.google.cloud.dataflow.examples.MinimalWordCount you will use the name my.java.project.MinimalWordCount , where my.java.project is whatever package name you chose when you created the project.

Or if you have cloned the SDK itself from GoogleCloudPlatform/DataflowJavaSDK then you will need to add -pl examples to your command line. This is because the SDK's repository is factored into maven modules; this flag instructs maven to run in the context of the examples module.

Answer 2

如果您有一个多模块Maven项目（DataflowJavaSDK，而不是DataflowJavaSDK-examples），则可以在顶层目录中执行mvn compile ，然后在cd插入examples ，然后在其中mvn exec:java -Dexec.mainClass=...命令。