How do inject properties or environment variables into my Maven plugin testcase? -

I've created a Maven plugin using and I'm trying to check it out.

I'm using to test and I'm having trouble giving injections to values ​​for my plugin parameters.

I have the following pom.xml file ( src / test / resources / pom.xml ) for testing:

  & lt; Project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns: xsi = "http: // www. W3.org/2001/XMLSchema-instance" xsi: schema location = "http: / /maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd "& gt; & Lt; ModelVersion & gt; 4.0.0 & lt; / ModelVersion & gt; & Lt; Group & gt; Com.vodori.pepper.docker.vm.unit & lt; / Group & gt; & Lt; ArtifactId & gt; Test pom & lt; / ArtifactId> & Lt; Version & gt; 1.0-snapshots & lt; / Edition & gt; & Lt; Packaging & gt; Jar & lt; / Packaging & gt; & Lt; Name & gt; Exam VMStarter & lt; / Name & gt; & Lt; Dependency & gt; & Lt; Dependency & gt; & Lt; Group & gt; JUnit & lt; / Group & gt; & Lt; ArtifactId & gt; JUnit & lt; / ArtifactId> & Lt; Version & gt; 4.11 & lt; / Edition & gt; & Lt; Scope & gt; Trial & lt; / Scope & gt; & Lt; / Dependencies & gt; & Lt; / Dependencies & gt; & Lt; Construction & gt; & Lt; Plugins & gt; & Lt; Plugin & gt; & Lt; Group & gt; Com.vodori.common & lt; / Group & gt; & Lt; ArtifactId & gt; Black Pepper-Docher-VM & lt; / ArtifactId> & Lt; Version & gt; 1.0.1-Snapshot & lt; / Edition & gt; & Lt; Configuration & gt; & Lt; DockerSnapshotSite & gt; Black pepper-demo site & lt; / DockerSnapshotSite & gt; & Lt; DockerSnapshotVersion & gt; 3.6.11 & lt; / DockerSnapshotVersion & gt; & Lt; / Configuration & gt; & Lt; / Plugin & gt; & Lt; / Plugins & gt; & Lt; / Create & gt; & Lt; / Project & gt;   
 My mojo looks like this (at the top):  
  Public abstract class VMPlugin extends AbstractMojo {/ ** * Docker location * / @Parameter (essential = true, property = "docker.", Defaultwall = "$ {env.DOCKER_LOCATION}") string dock path; Public Zero Set Dokterpath (String Dock Path) {this.dockerpath = Dokterpath; } / ** * Doker VM site name * / @ parameter (required = true, property = "docker scapshot.") String Docker snapshot site; / ** * Version of the dockkey snapshot / @ parameter (required = true, property = "docker snapshot.version") string docker snapshot version;   
 I am using the approach for testing and my setup method looks like this:  
  @ throws public first zero exceptions (exceptions) Exception {vmStarter = (VMStarter) rule.lookupMojo ("Start- docker-vm", "src / test / resources / pom.xml"); AssertNotNull (vmStarter); }   
 I use setter for some of my tests (which tests  bad  docker locations), but for my good path testing, I Environmental variable  DOCKER_LOCATION  for population, however, for some reason,  Docarpath  is now visible as  null . It looks like  defaultValue  is being ignored.  
 I have tried to dump  System.getEnv ()  on STDERR and I can see that  DOCKER_LOCATION  is  in fact  set.  
 What am I missing here? Why not my  @Parameter  being populated correctly?   
 
 
 Where did you do syntax  default value = "$ {env.DOCKER_LOCATION}"  From?  
  and *  another  "You can use Maven in a pom.xml file or in any resource that is being processed by the MyOne resource plug-in filtering features."   
  Default-value   
 is mentioned:  "(More can be found in" Parameter Expression "document)"  .  But I have not found any such document yet.  Thx @khmarbaise:.  
  $ {env}  does not show with my Maven 3.2.1.  
 Although it is my experience that at least some, if not all, the latest information of the connected docks and not the latest enhancements.  
 A possible interpretation program logic point of view: If a default value is set out from the scope of a program, then it can not be considered as the default value. In the sense of Maven  
 EDIT:  Added Expression Document