Custom Nifi processor throwing build error : Null Pointer Exception from Nifi nar maven plugin

Question

I am trying to build custom nifi processor with controller service, I have configured projects setting to build nar files, while building getting following error, this looks to be from nifi libraries, plz let me know is there any solution or workaround exiting for this.This looks to be nif-nar-maven-plugin issue, could problem with version!!

[INFO] Generating documentation for NiFi extensions in the NAR... [INFO] Found a dependency on version 1.11.4 of NiFi API
[ERROR] Could not generate extensions' documentation
org.apache.maven.plugin.MojoExecutionException: Failed to create Extension Documentation
at org.apache.nifi.NarMojo.generateDocumentation (NarMojo.java:596)
at org.apache.nifi.NarMojo.execute (NarMojo.java:499)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:567)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
Caused by: java.lang.NullPointerException
at org.apache.nifi.NarMojo.getRequiredServiceDefinitions (NarMojo.java:708)
at org.apache.nifi.NarMojo.writeDocumentation (NarMojo.java:634)
at org.apache.nifi.NarMojo.writeDocumentation (NarMojo.java:605)
at org.apache.nifi.NarMojo.generateDocumentation (NarMojo.java:577)
at org.apache.nifi.NarMojo.execute (NarMojo.java:499)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:567)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for custom-processor 1.0-SNAPSHOT:
[INFO]
[INFO] custom-processor ................................... SUCCESS [ 6.729 s]
[INFO] nifi-sample-api .................................... SUCCESS [ 4.566 s]
[INFO] nifi-sample ........................................ SUCCESS [ 12.118 s]
[INFO] nifi-custom-processors ............................. SUCCESS [ 10.350 s]
[INFO] nifi-custom-nar .................................... FAILURE [ 4.535 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 44.067 s
[INFO] Finished at: 2020-04-06T22:23:28+05:30
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.nifi:nifi-nar-maven-plugin:1.3.1:nar (default-nar) on project nifi-custom-nar: Failed to create Extension Documentation: NullPointerException -> [Help

I have used latest Nifi version, the contents of maven-plugin directory find from attachment, any help greatly appreciated.

Would most likely need to see the code for your processors and services and possibly the poms — Bryan Bende
@Byan, I have not put my code any thing in the custom processor except adding the service properties, its basic build, and i have not mentioned nif-nar-maven-plugin any where in the pom, its downloading from dependencies. — user2927486
Have you tried this reference ? It will be somewhat answer your question . medium.com/hashmapinc/… — kaviranga
It is related to the property descriptor that references the service, can you show that? — Bryan Bende
@Kaviranga, I have followed same link as reference to build custom processor, but still getting the issue. — user2927486

Javi Alsina Javi Alsina · Accepted Answer · 2020-09-22T10:11:14

You should add the following dependency in the nar child project's pom file.

    <dependency>
        <groupId>org.apache.nifi</groupId>
        <artifactId>nifi-standard-services-api-nar</artifactId>
        <version>1.11.4</version>
        <type>nar</type>
    </dependency>

Custom Nifi processor throwing build error : Null Pointer Exception from Nifi nar maven plugin

1 Answers