Null Pointer Exception - Need better error message

[JenCoston]

My code is throwing a null pointer exception when I add the swagger-maven-plugin to my pom.xml file. It runs without it and I can access both the api and the swagger ui. From the console output it looks like the error may be thrown when trying to scan the target classes. Is there a way to get a more helpful error message?

Here is the console output:
[DEBUG] going to scan these urls:
file:/C:/Swagger/HelloService/MyApp/HelloService/target/classes/
[INFO] Reflections took 124 ms to scan 1 urls, producing 17 keys and 29 values
[DEBUG] resolveProperty void
[DEBUG] resolveProperty [simple type, class void]
[DEBUG] resolve [simple type, class void]
[DEBUG] trying extension com.github.kongchen.swagger.docgen.reader.ModelModifier@5ee77baf
[DEBUG] Can't check class [simple type, class void], void
[DEBUG] defineModel void io.swagger.models.ModelImpl@bafd15c1
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 16.039 s
[INFO] Finished at: 2016-06-22T09:04:41-04:00
[INFO] Final Memory: 27M/409M
[INFO] ------------------------------------------------------------------------

Here is the error message:
[ERROR] Failed to execute goal com.github.kongchen:swagger-maven-plugin:3.1.2:generate (default) on project HelloService: null: MojoExecutionException: NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal com.github.kongchen:swagger-maven-plugin:3.1.2:generate (default) on project HelloService: null
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)
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:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
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.MojoExecutionException
at com.github.kongchen.swagger.docgen.mavenplugin.ApiDocumentMojo.execute(ApiDocumentMojo.java:114)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
... 20 more
Caused by: java.lang.NullPointerException
at com.github.kongchen.swagger.docgen.reader.AbstractReader.updateApiResponse(AbstractReader.java:470)
at com.github.kongchen.swagger.docgen.reader.JaxrsReader.parseMethod(JaxrsReader.java:318)
at com.github.kongchen.swagger.docgen.reader.JaxrsReader.read(JaxrsReader.java:93)
at com.github.kongchen.swagger.docgen.reader.JaxrsReader.read(JaxrsReader.java:50)
at com.github.kongchen.swagger.docgen.reader.JaxrsReader.read(JaxrsReader.java:41)
at com.github.kongchen.swagger.docgen.mavenplugin.MavenDocumentSource.loadDocuments(MavenDocumentSource.java:46)
at com.github.kongchen.swagger.docgen.mavenplugin.ApiDocumentMojo.execute(ApiDocumentMojo.java:84)
... 22 more
[ERROR]

Here is the plugin from the pom.xml file:
<!-- Swagger Plugin to Generate YAML/JSON Files at Compile Time --> <plugin> <groupId>com.github.kongchen</groupId> <artifactId>swagger-maven-plugin</artifactId> <version>3.1.2</version> <configuration> <apiSources> <apiSource> <springmvc>false</springmvc> <locations>com.mt.company.swagger.api</locations> <info> <title>Swagger Generated Files Example</title> <version>v1</version> <description>This is an example of the generated swagger files</description> </info> <outputFormats>json,yaml</outputFormats> <swaggerDirectory>${basedir}\src\main\resources</swaggerDirectory><!--directory the generated file will be put in --> <attachSwaggerArtifact>true</attachSwaggerArtifact> </apiSource> </apiSources> </configuration> <executions> <execution> <phase>compile</phase> <goals> <goal>generate</goal> </goals> </execution> </executions> </plugin>

[JenCoston]

Hello,

When I updated the jar from version 3.1.2 to 3.1.3 this error went away. Is version 3.1.2 no longer supported?

Thanks!

[carlosjgp]

Maybe this version changed is related with some bug fixes...? And probably NullPointerException is one of them