[MNG-6004] Emit better error message for simple XML typos

[jira-importer]

Archie Cobbs opened MNG-6004 and commented

When porting a project from ant to maven, I accidentally said this:

<configuration>
  <links>
    <link href="http://www.slf4j.org/api/"/>
  </links>
</configuration>

instead of this:

<configuration>
  <links>
    <link>http://www.slf4j.org/api/</link>
  </links>
</configuration>

Easy enough mistake to make. However, the error message was utterly mystifying:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:jar (attach-javadocs) on project msrp4j: Execution attach-javadocs of goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:jar failed. NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:jar (attach-javadocs) on project msrp4j: Execution attach-javadocs of goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:jar failed.
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:224)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:120)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:355)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:155)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:584)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:216)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:160)
	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: org.apache.maven.plugin.PluginExecutionException: Execution attach-javadocs of goal org.apache.maven.plugins:maven-javadoc-plugin:2.9.1:jar failed.
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:143)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
	... 19 more
Caused by: java.lang.NullPointerException
	at org.codehaus.plexus.util.xml.pull.MXSerializer.writeElementContent(MXSerializer.java:921)
	at org.codehaus.plexus.util.xml.pull.MXSerializer.text(MXSerializer.java:785)
	at org.apache.maven.plugin.javadoc.options.io.xpp3.JavadocOptionsXpp3Writer.writeJavadocOptions(JavadocOptionsXpp3Writer.java:268)
	at org.apache.maven.plugin.javadoc.options.io.xpp3.JavadocOptionsXpp3Writer.write(JavadocOptionsXpp3Writer.java:70)
	at org.apache.maven.plugin.javadoc.AbstractJavadocMojo.buildJavadocOptions(AbstractJavadocMojo.java:5867)
	at org.apache.maven.plugin.javadoc.AbstractJavadocMojo.executeReport(AbstractJavadocMojo.java:1857)
	at org.apache.maven.plugin.javadoc.JavadocJar.execute(JavadocJar.java:181)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:132)
	... 20 more

Suggestion: include code that performs basic structural checks so as to make it impossible for a cryptic NullPointerException to occur simply due to incorrect POM input.

---

Affects: 3.3.9

1 votes, 4 watchers

[jira-importer]

Michael Osipov commented

Moved to Maven. This cannot be fixed on a per plugin level but must be fixed by the entire ecosystem in general. It won't probably never be implemented. JAXB doesn't provide you hints too that your XML does not correspond to the desired model.

[jira-importer]

Elliotte Rusty Harold commented

Yes, this could be done. Ideally we won't use JAXB at all, (deprecated in java 9+ and it was not a good idea in the first place) but short of ripping it out and replacing it with something better, we could add a preprocessing validation step with better error messages.