[MNG-5633] NullPointerException when project contains cyclic references

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Flags: Patch
• Assignee: Unassigned
• Reporter: Gabriel Reid
• Created: 13/May/14 07:38
• Updated: 06/Jan/16 19:52
• Resolved: 22/May/14 17:45

Description

Using maven 3.2.1, when a project has a cyclic dependency between modules, a NullPointerException is thrown.

The situation is that there is a root pom that references two modules, a and b. Module a is dependent on b, and module b is dependent on a.

The relevant portions of the poms are as follows:

root pom

<project>
  <modelVersion>4.0.0</modelVersion>

  <groupId>test</groupId>
  <artifactId>invalid</artifactId>
  <version>0.1-SNAPSHOT</version>
  <packaging>pom</packaging>

  <modules>
    <module>a</module>
    <module>b</module>
  </modules>

  <dependencyManagement>
    <dependencies>
    <dependency>
      <groupId>test</groupId>
      <artifactId>a</artifactId>
      <version>${project.version}</version>
    </dependency>
    <dependency>
      <groupId>test</groupId>
      <artifactId>b</artifactId>
      <version>${project.version}</version>
    </dependency>
    </dependencies>
  </dependencyManagement>
</project>

a/pom.xml

<project>
  <modelVersion>4.0.0</modelVersion>

  <groupId>test</groupId>
  <artifactId>a</artifactId>

  <parent>
    <groupId>test</groupId>
    <artifactId>invalid</artifactId>
    <version>0.1-SNAPSHOT</version>
  </parent>
  <dependencies>
    <dependency>
      <groupId>test</groupId>
      <artifactId>b</artifactId>
    </dependency>
  </dependencies>
</project>

a/pom.xml

<project>
  <modelVersion>4.0.0</modelVersion>

  <groupId>test</groupId>
  <artifactId>b</artifactId>

  <parent>
    <groupId>test</groupId>
    <artifactId>invalid</artifactId>
    <version>0.1-SNAPSHOT</version>
  </parent>
  <dependencies>
    <dependency>
      <groupId>test</groupId>
      <artifactId>a</artifactId>
    </dependency>
  </dependencies>
</project>

Running a simple maven command such as "mvn clean" results in the following:

$ mvn clean
[INFO] Scanning for projects...
[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

Issue Links

• is related to: MNG-5628 NullPointerException with Maven 3.2.1 when circular dependency exists in POMs
• relates to: MNG-5637 NPE in org.apache.maven.DefaultMaven.execute()