Maven: Cannot get the help goals working (clean:help, compiler:help, etc)

Question

I am new in Maven. Do you know what I am doing wrong (see below)?

---

mvn -e clean:help.  
+ Error stacktraces are turned on.  
[INFO] Scanning for projects...  
[INFO] Searching repository for plugin with prefix: 'clean'.  
[INFO] ------------------------------------------------------------------------ 
[ERROR] BUILD FAILURE  
[INFO] ------------------------------------------------------------------------  
[INFO] Required goal not found: clean:help in org.apache.maven.plugins:maven-clean-plugin:2.2  
[INFO] ------------------------------------------------------------------------  
[INFO] Trace  
org.apache.maven.BuildFailureException: Required goal not found: clean:help in org.apache.maven.plugins:maven-clean-plugin:2.2
    at   org.apache.maven.lifecycle.DefaultLifecycleExecutor.getMojoDescriptor(DefaultLifecycleExecutor.java:1867)
    at   org.apache.maven.lifecycle.DefaultLifecycleExecutor.segmentTaskListByAggregationNeeds(DefaultLifecycleExecutor.java:462)
    at   org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:175)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)

Answer 1

I think you want:

mvn help:describe -Dcmd=clean

which gives:

[INFO] [help:describe {execution: default-cli}]
[INFO] 'clean' is a lifecycle with the following phases: 
* pre-clean: Not defined
* clean: org.apache.maven.plugins:maven-clean-plugin:clean
* post-clean: Not defined

See here for more details and examples. The same applies for compile.

mvn help:describe -Dcmd=compile

Answer 2

The version of the plugin you are using on the command line (2.2) does not have the clean:help goal (since 2.3). Try this instead:

mvn org.apache.maven.plugins:maven-clean-plugin:2.4:help