Maven project version inheritance - do I have to specify the parent version

Question

I have two projects  Parent project  A  Sub project  B  A pom xml    lt groupId gt com dummy bla lt  groupId gt   lt artifactId gt parent lt  artifactId gt   lt version gt 0 1-SNAPSHOT lt  version gt   lt packaging gt pom lt  packaging gt    And in B pom xml  I have        lt parent gt           lt groupId gt com dummy bla lt  groupId gt           lt artifactId gt parent lt  artifactId gt           lt version gt 0 1-SNAPSHOT lt  version gt            lt  parent gt        lt groupId gt com dummy bla sub lt  groupId gt       lt artifactId gt kid lt  artifactId gt    I want B to inherit the version from parent  so the only place in my case I need to put 0 1-SNAPSHOT is A pom xml  But if i remove the  lt version gt 0 1-SNAPSHOT lt  version gt  from B pom xml under the parent section  maven complains about the missing version for the parent    Is there a way I can just use   project version  or something like this to avoid having 01 -SNAPSHOT in both poms

User · Answer

eFox s answer worked for a single project  but not when I was referencing a module from another one  the pom xml were still stored in my  m2 with the property instead of the version     However  it works if you combine it with the flatten-maven-plugin  since it generates the poms with the correct version  not the property    The only option I changed in the plug-in definition is the outputDirectory  it s empty by default  but I prefer to have it in target  which is set in my  gitignore configuration    lt plugin gt      lt groupId gt org codehaus mojo lt  groupId gt      lt artifactId gt flatten-maven-plugin lt  artifactId gt      lt version gt 1 0 1 lt  version gt      lt configuration gt         lt updatePomFile gt true lt  updatePomFile gt         lt outputDirectory gt target lt  outputDirectory gt      lt  configuration gt      lt executions gt         lt execution gt            lt id gt flatten lt  id gt            lt phase gt process-resources lt  phase gt            lt goals gt               lt goal gt flatten lt  goal gt            lt  goals gt         lt  execution gt      lt  executions gt   lt  plugin gt    The plug-in configuration goes in the parent pom xml

User · Answer

EDIT  Since Maven 3 5 0 there is a nice solution for this using   revision  placeholder  See FrVaBe s answer for details  For previous Maven versions see my original answer below     No  there isn t  You always have to specify parent s version  Fortunately  it is inherited as the module s version what is desirable in most cases  Moreover  this parent s version declaration is bumped automatically by Maven Release Plugin  so - in fact - it s not a problem that you have version in 2 places as long as you use Maven Release Plugin for releasing or just bumping versions   Notice that there are some cases when this behaviour is actually pretty OK and gives more flexibility you may need  Sometimes you want to use some of previous parent s version to inherit  however that s not a mainstream case

User · Answer

Use mvn -N versions update-child-modules to update child pom s version  https   www mojohaus org versions-maven-plugin examples update-child-modules html

User · Answer

The easiest way to update versions IMO     mvn versions set -DgenerateBackupPoms false    do that in your root parent pom folder    Your POMs are parsed and you re asked which version to set

User · Answer

lt parent gt       lt groupId gt com dummy bla lt  groupId gt       lt artifactId gt parent lt  artifactId gt       lt version gt 0 1-SNAPSHOT lt  version gt         lt  parent gt     lt groupId gt com dummy bla sub lt  groupId gt    lt artifactId gt kid lt  artifactId gt    You mean you want to remove the version from parent block of B s pom  I think you can not do it  the groupId  artifactId  and version specified the parent s pom coordinate s  what you can omit is child s version

User · Answer

You could also use     mvn release update-versions -DdevelopmentVersion  version    to update the version numbers in your POMs

User · Answer

Since Maven 3 5 0 you can use the   revision  placeholder for that  The use is documented here  Maven CI Friendly Versions   In short the parent pom looks like this  quoted from the Apache documentation     lt project gt     lt modelVersion gt 4 0 0 lt  modelVersion gt     lt parent gt       lt groupId gt org apache lt  groupId gt       lt artifactId gt apache lt  artifactId gt       lt version gt 18 lt  version gt     lt  parent gt     lt groupId gt org apache maven ci lt  groupId gt     lt artifactId gt ci-parent lt  artifactId gt     lt name gt First CI Friendly lt  name gt     lt version gt   revision  lt  version gt           lt properties gt       lt revision gt 1 0 0-SNAPSHOT lt  revision gt     lt  properties gt     lt modules gt       lt module gt child1 lt  module gt            lt  modules gt   lt  project gt    and the child pom like this   lt project gt     lt modelVersion gt 4 0 0 lt  modelVersion gt     lt parent gt       lt groupId gt org apache maven ci lt  groupId gt       lt artifactId gt ci-parent lt  artifactId gt       lt version gt   revision  lt  version gt     lt  parent gt     lt groupId gt org apache maven ci lt  groupId gt     lt artifactId gt ci-child lt  artifactId gt          lt  project gt    You also have to use the Flatten Maven Plugin to generate pom documents with the dedicated version number included for deployment  The HowTo is documented in the linked documentation   Also  khmarbaise wrote a nice blob post about this feature  Maven  POM Files Without a Version in It

User · Answer

As Yanflea mentioned  there is a way to go around this   In Maven 3 5 0 you can use the following way of transferring the version down from the parent project   Parent POM xml   lt project     gt       lt modelVersion gt 4 0 0 lt  modelVersion gt       lt groupId gt com mydomain lt  groupId gt       lt artifactId gt myprojectparent lt  artifactId gt       lt packaging gt pom lt  packaging gt       lt version gt   myversion  lt  version gt       lt name gt MyProjectParent lt  name gt        lt properties gt           lt myversion gt 0 1-SNAPSHOT lt  myversion gt       lt  properties gt        lt modules gt           lt module gt modulefolder lt  module gt       lt  modules gt           lt  project gt    Module POM xml   lt project     gt       lt modelVersion gt 4 0 0 lt  modelVersion gt        lt parent gt           lt groupId gt com mydomain lt  groupId gt           lt artifactId gt myprojectmodule lt  artifactId gt           lt version gt   myversion  lt  version gt   lt  -- This still needs to be set  but you can use properties from parent -- gt       lt  parent gt        lt groupId gt se car o liner lt  groupId gt       lt artifactId gt vinno lt  artifactId gt       lt packaging gt war lt  packaging gt       lt name gt Vinno lt  name gt       lt  -- Note that there s no version specified  it s inherited from parent -- gt           lt  project gt    You are free to change myversion to whatever you want that isn t a reserved property

User · Answer

Maven is not designed to work that way  but a workaround exists to achieve this goal  maybe with side effects  you will have to give a try   The trick is to tell the child project to find its parent via its relative path rather than its pure maven coordinates  and in addition to externalize the version number in a property    Parent pom     lt groupId gt com dummy bla lt  groupId gt   lt artifactId gt parent lt  artifactId gt   lt version gt   global version  lt  version gt   lt packaging gt pom lt  packaging gt    lt properties gt      lt  -- Unique entry point for version number management -- gt       lt global version gt 0 1-SNAPSHOT lt  global version gt   lt  properties gt    Child pom   lt parent gt      lt groupId gt com dummy bla lt  groupId gt      lt artifactId gt parent lt  artifactId gt      lt version gt   global version  lt  version gt      lt relativePath gt    lt  relativePath gt       lt  parent gt    lt groupId gt com dummy bla sub lt  groupId gt   lt artifactId gt kid lt  artifactId gt    I used that trick for a while for one of my project  with no specific problem  except the fact that maven logs a lot of warnings at the beginning of the build  which is not very elegant   EDIT  Seems maven 3 0 4 does not allow such a configuration anymore

[inheritance] Maven project version inheritance - do I have to specify the parent version?

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