Version Management in Maven


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Version Management in Maven

  1. 1. Version Mgmt in Maven SOME BEST PRACTICES
  2. 2. Agenda What is software versioning How can maven help us? ◦ Maven release plugin Best practices ◦ What to version? ◦ How to manage versions? Tips and tricks ◦ Version handling with maven-versions-plugin ◦ Dependency analysis with maven-dependency-plugin
  3. 3. Version identifies software artefacts: Software Versioning ◦ modules, applications, assemblies, … ◦ Uniquely identifies source code ◦ Build should be repeatable from that version of code Most used: ◦ Major.minor[.bugfix][-qualifier[-build]] Qualifiers: ◦ ◦ ◦ ◦ ◦ Alpha: not feature complete Beta: contains critical bugs CR: release candidate, not fully tested Final: final version SNAPSHOT ◦ Floating version, not an actual identification ◦ Should allways be used for code under development
  4. 4. Versioning with Source Code Management Basics of SCM (Git, Subversion, CVS, …) ◦ Synching software changes between developers ◦ Allowing multiple branches to be developed simultaneously ◦ Maintenance branches ◦ Feature branches ◦ Merge branches again  ◦ Tagging versions of code ◦ So you can find out later which bugs you solved when SCM does not put a version number in your artifacts!
  5. 5. Maven in a nutshell
  6. 6. Maven Basics Convention over configuration ◦ Convention for source code organization ◦ src/main/java ◦ src/webapp ◦ src/test/java ◦ Plugins with default configurations ◦ Jar, war, ear ◦ Surefire tests ◦ Reporting Dependency Management ◦ Remote repository and local repository ◦ Transactional dependencies
  7. 7. Snapshots In maven, versions under development have classifier ‘-SNAPSHOT’ ◦ When building versions on a development system, you should always build SNAPSHOTS. ◦ When depending on a SNAPSHOT version of another module, maven will give you the latest (timestamped) version ◦ Could give surprises of code that suddenly stops building ◦ Preferrably have the source code of your SNAPSHOT dependencies built locally Non SNAPSHOT versions should be built only once and deployed once ◦ Should be tagged in Subversion/Git/CVS, and never changed ◦ (Unless you know for sure nobody got a copy yet) ◦ Released versions should never have SNAPSHOT dependencies ◦ See release plugin later
  8. 8. Organizing Maven Modules Aggregator POM vs. Parent POM ◦ Aggregator POM organizes build of multiple modules ◦ One per subfolder ◦ Declares which subfolders contain modules ◦ Parent POM centralizes common configuration ◦ Plugin configuration ◦ Dependencies ◦ Dependency Management Convention: Aggregator POM == Parent POM ◦ Exceptions are allowed
  9. 9. Typical Maven Workspace Hierarchy Workspace POM ◦ Godfather aka archon (development team) ◦ Application System(s) (set of related applications) ◦ Application or Library ◦ Module Group(s) (if necessary) ◦ Module
  10. 10. Workspace POM Dummy Aggregator POM Just to launch other POM’s Can use symbolic links to point to actual application roots to be built.
  11. 11. Godfather POM Defines <distributionManagement> and <repositories> ◦ <distributionManagement>: where your artifacts are deployed ◦ <repositories>: where other necessary artifacts can be found Rarely changes ◦ Simple fixed version number, e.g. 1, 2, 3, … Do not put shared dependencies here ◦ Use maven import (since maven 2.0.9)
  12. 12. Application System POM Inherits from Godfather Defines external dependency versions in <dependencyManagement> Defines common plugin configuration ◦ E.g. java compiler version Could build an assembly containing all applications
  13. 13. Application or Library POM Module groups Defines internal dependency management ◦ Sibling modules ◦ Can use ${project.version} Define more shared configuration ◦ Inapplicable on a higher level ◦ E.g. aspect jars to use
  14. 14. Module POM Defines all direct dependencies ◦ Do not rely on transitive dependencies ◦ Use scopes when applicable ◦ ◦ ◦ ◦ Compile Runtime (e.g. JDBC Drivers) Test (e.g. JUnit, DBUnit) Provided (e.g. Java EE jars)
  15. 15. Maven release plugin mvn release:prepare release:perform ◦ Verifies if you checked in everything ◦ Verifies if you have SNAPSHOT dependencies ◦ outside the current released modules ◦ Tries to build and test your modules ◦ Updates the version to the release version and tags it in SCM ◦ Recursively ◦ Checks out the tagged version and build and deploys the release version ◦ Updates the version to the next SNAPSHOT version and checks it in ◦ Recursively
  16. 16. Maven release plugin prerequisites <distributionManagement> ◦ in godfather POM ◦ point to repository server (nexus) <server> with login for repository ◦ authorized to deploy ◦ in settings.xml <scm> tag ◦ Point to subversion/git/CVS
  17. 17. Demo1 Command line release cascade Jenkins demo
  18. 18. What to Version / What to release Could be: Individual Modules, Applications, Application System? Depends on the lifecycle of your product ◦ Do you want to deploy/upgrade a single module or application? ◦ Can you test a single module? ◦ Can you test an application without testing the rest of the application system? ◦ Can you trace bugs in one application without knowing what other applications are running?
  19. 19. What if… you release individual modules Every module can have its own version Maintenance releases with individual modules ◦ Dependants can stick to release versions if they want ◦ For big refactorings you need snapshot dependencies Need big cascaded release to build a new version
  20. 20. What if… you version an application system Only one version to manage Release all at once Every change need a full release
  21. 21. Mix and match Release some individual modules ◦ Those that are used in multiple applications Release some applications as a whole ◦ Applications in maintenance Release some application systems ◦ With strong intra-application dependencies
  22. 22. More interesting plugins maven-help-plugin ◦ mvn help:effective-pom maven-dependency-plugin ◦ mvn dependency:tree ◦ mvn dependency:analyze ◦ mvn dependency:analyze-dep-mgmt maven-versions-plugin ◦ mvn versions:use-next-snapshots -DexcludeReactor=false -Dincludes=group:* ◦ mvn versions:update-child-modules
  23. 23. Demo2 maven-help-plugin maven-dependency-plugin maven-versions-plugin
  24. 24. Questions