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https://issues.apache.org/jira/browse/MNG-6495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16668887#comment-16668887
]
Elliotte Rusty Harold commented on MNG-6495:
--------------------------------------------
I think this is the code where I stumbled onto this. Looks like I since added a
ModelResolver to avoid the issue, but try setting that to null instead and see
what happens.
package com.google.cloud.tools.opensource.dependencies;
import java.net.MalformedURLException;
import java.net.URL;
import org.apache.maven.building.UrlSource;
import org.apache.maven.model.Model;
import org.apache.maven.model.building.DefaultModelBuilder;
import org.apache.maven.model.building.DefaultModelBuilderFactory;
import org.apache.maven.model.building.DefaultModelBuildingRequest;
import org.apache.maven.model.building.ModelBuildingException;
import org.apache.maven.model.building.ModelBuildingRequest;
import org.apache.maven.model.building.ModelBuildingResult;
import org.apache.maven.model.building.ModelSource;
import org.apache.maven.model.building.UrlModelSource;
import org.apache.maven.model.resolution.ModelResolver;
import org.apache.maven.model.resolution.UnresolvableModelException;
import org.apache.maven.project.ProjectModelResolver;
import org.eclipse.aether.artifact.DefaultArtifact;
import org.eclipse.aether.collection.DependencyCollectionException;
import org.eclipse.aether.resolution.DependencyResolutionException;
public class MetadataExplorer {
public static void main(String[] args)
throws DependencyCollectionException, DependencyResolutionException,
MalformedURLException, UnresolvableModelException {
try {
DefaultArtifact artifact = new
DefaultArtifact("com.google.guava:guava:26.0-jre");
DefaultModelBuilder modelBuilder = new
DefaultModelBuilderFactory().newInstance();
ModelBuildingRequest request = new DefaultModelBuildingRequest();
URL pomUrl = new URL(
"https://repo1.maven.org/maven2/com/google/guava/guava/26.0-jre/guava-26.0-jre.pom";);
UrlModelSource source = new UrlModelSource(pomUrl);
request.setModelSource(source);
ProjectModelResolver modelResolver
= new ProjectModelResolver(null, null, null, null, null, null, null);
ModelSource s = modelResolver.resolveModel("com.google.guava", "guava",
"26.0-jre");
request.setModelResolver(modelResolver);
ModelBuildingResult result = modelBuilder.build(request);
Model model = result.getEffectiveModel();
System.out.println(model.getArtifactId());
} catch (IllegalArgumentException ex) {
System.err.println("Bad Maven coordinates " + args[0]);
return;
} catch (ModelBuildingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
> ModelResolver cannot be null
> ----------------------------
>
> Key: MNG-6495
> URL: https://issues.apache.org/jira/browse/MNG-6495
> Project: Maven
> Issue Type: Bug
> Components: Bootstrap & Build
> Affects Versions: 3.5.4
> Reporter: Elliotte Rusty Harold
> Priority: Major
>
> Got this exception stacktrace while writing some of my own code today:
> {noformat}
> Exception in thread "main" java.lang.NullPointerException:
> request.modelResolver cannot be null (parent POM
> com.google.guava:guava-parent:26.0-jre and POM
> com.google.guava:guava:[unknown-version])
> at org.apache.commons.lang3.Validate.notNull(Validate.java:225)
> at
> org.apache.maven.model.building.DefaultModelBuilder.readParentExternally(DefaultModelBuilder.java:1046)
> at
> org.apache.maven.model.building.DefaultModelBuilder.readParent(DefaultModelBuilder.java:830)
> at
> org.apache.maven.model.building.DefaultModelBuilder.build(DefaultModelBuilder.java:332)
> at
> com.google.cloud.tools.opensource.dependencies.MetadataExplorer.main(MetadataExplorer.java:50)
> {noformat}
> No big deal except that the JavaDoc at
> [ModelBuildingRequest|http://maven.apache.org/ref/3.5.4/maven-model-builder/apidocs/org/apache/maven/model/building/ModelBuildingRequest.html]
> says "The model resolver to use, may be null."
> Not sure whether to update the docs or the code here.
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