CODEWITHSUNDEEP
javamaven
daydreamer
daydreamer

Reputation: 91969

Maven: How can I have a module with same name under two different modules?

Consider this structure

project
       pom.xml
       component1/
                 pom.xml
                 persistence/pom.xml
                 business/pom.xml
                 rest/pom.xml
       component2/
                 pom.xml
                 persistence/pom.xml
                 business/pom.xml
                 rest/pom.xml

When I try to do this, I get NullPointerException

[ERROR] Internal error: java.lang.NullPointerException -> [Help 1]
org.apache.maven.InternalErrorException: Internal error: java.lang.NullPointerException
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:167)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:584)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:213)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:157)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: java.lang.NullPointerException
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:270)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:155)
    ... 11 more
[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/InternalErrorException

Can I not have a structure like this? I am using Maven 3.2.1

This is how component2/pom.xml looks

<parent>
    <groupId>com.org</groupId>
    <artifactId>component2</artifactId>
    <version>1.0-SNAPSHOT</version>
</parent>

<artifactId>persistence</artifactId>
<version>1.0-SNAPSHOT</version>

This is same as component1/pom.xml except parent

<modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>com.org</groupId>
    <artifactId>component1</artifactId>
    <version>1.0-SNAPSHOT</version>
</parent>
<artifactId>persistence</artifactId>
<packaging>pom</packaging>

When I try to have a different module name, it works

Upvotes: 1

Views: 3293

Answers (2)

tmarwen
tmarwen

Reputation: 16354

Not only maven gets will be confused with actual layering of your project, but some day you will get lost with both modules and you won't know which one is this or that.

So as @Raghuram pointed out you will need a unique identifier for each module, thus by having a unique groupId or unique artifcatId (Within scope of your project and even respecting other artifacts or you will get weird conflicts).

This is for uniqueness purpose, but some conventions should be followed and you will automatically get your self out of any troubles that could be caused by modules/projects naming:

  • goupId: A universally unique identifier for a project. It is normal to use a fully-qualified package name to distinguish it from other projects with a similar name (eg. org.apache.maven).

  • artifactId: The identifier for this artifact that is unique within the group given by the group ID.

Just follow those lines and you'll be not even safe but producing packages respecting practice rules.

Upvotes: 0

Raghuram
Raghuram

Reputation: 52645

As @jigar-joshi has indicated, maven needs a way to distinguish between the persistence module of component1 and persistence module of component2. The way it does is by by the combination of groupId and artifactId. This combination needs to be unique for each persistence module (or business and rest for that matter).

So, either each persistence needs to have a unique groupId (say com.org.component1 and com.org.component2) or a unique artifactId (component1-persistence and component2-persistence).

Upvotes: 1

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