Is there a Java Class that generates a POM.xml file?

Question

In my job project I have recently been asked to generate POM files via a java class. The problem is that I am very, very new to Maven (like since last December).

Wha

Answer 1

To generate pom with multiple dependencies, you can use the following sample code:

Model model = new Model();  
Writer writer = new FileWriter("C:/GRADLE_WORKSPACE/test.pom");  
List<Dependency> dependencyList = new ArrayList<Dependency>();  

model.setGroupId( "TestGroupArtifactID" );    
model.setArtifactId("TestGroupArtifactName");    
model.setVersion("1.0.0");    

Dependency dep = new Dependency();    
dep.setGroupId("TestGroupId");    
dep.setArtifactId("TestDependencyName");    
dep.setVersion("1.0.0");
dependencyList.add(dep);

Dependency dep2 = new Dependency();    
dep2.setGroupId("TestGroupId2");    
dep2.setArtifactId("TestDependencyName2");   
dep2.setVersion("2.0.0");     
dependencyList.add(dep2);       

//model.addDependency(dep);    
model.setDependencies(dependencyList);    
new MavenXpp3Writer().write(writer, model );    
writer.close();

Regards,
Srikanth Praveen

Answer 2

        MavenXpp3Reader reader = new MavenXpp3Reader();
        Model pomModel = reader.read(new FileReader(pomLibFile));
        final List<Dependency> dependencies= pomModel.getDependencies();
        final List<String> modules= pomModel.getModules();
        final List<Profile> profiles = pomModel.getProfiles();

        InputStream inputStream = new FileInputStream(new File(pomLibFile));
        StringWriter writer = new StringWriter();
        IOUtils.copy(inputStream, writer, "utf-8");
        pomModel.getDependencyManagement();
        final Properties properties = new Properties();
        properties.load(new FileInputStream(pomProperties));
        RegexBasedInterpolator interpolator = new RegexBasedInterpolator();

        interpolator.addValueSource( new EnvarBasedValueSource() );
        interpolator.addValueSource( new PropertiesBasedValueSource( properties ) );

        List<String> synonymPrefixes = new ArrayList<String>();
        synonymPrefixes.add( "project." );
        synonymPrefixes.add( "pom." );

        PrefixedValueSourceWrapper modelWrapper = new PrefixedValueSourceWrapper( new ObjectBasedValueSource( pomModel ),synonymPrefixes, true );
        interpolator.addValueSource( modelWrapper );

        PrefixedValueSourceWrapper pomPropertyWrapper = 
                new PrefixedValueSourceWrapper( new PropertiesBasedValueSource( pomModel.getProperties() ), synonymPrefixes,  true );
        interpolator.addValueSource( pomPropertyWrapper );

        interpolator.addValueSource( new PropertiesBasedValueSource( properties ) );

        RecursionInterceptor recursionInterceptor = new PrefixAwareRecursionInterceptor( synonymPrefixes, true );

        String serializedPOM = interpolator.interpolate( writer.toString(), recursionInterceptor );
        System.out.println("-------- "+serializedPOM);;

Reference : http://plexus.codehaus.org/plexus-components/plexus-interpolation/index.html

though I am still stuck if I have to add multiple (unknown number of) dependencies.

Answer 3

Why do you have to do it in java rather than using an existing tool such as m2eclipse.
See guide for creating a POM for an existing project using m2eclipse.

You could also see the m2eclipse developer guide which will let you see the source code for their implementation.

Reply----
This is a common problem encountered when trying to mavenise a project.
The biggest hurdle is trying to identify the correct maven coordinates.
Often projects refer to renamed jar files, where the group-id, and version numbers have been stripped off.

Sometimes inspecting the manifest in the jar-file gives some hints as to the correct dependent artifact.

Answer 4

It depends on what you are trying to do. If you just want to create POMs for new projects of a certainly type, the best way is through Maven archetypes (you can create your own archetypes with the templates you want).

If you really have a need to programmatically write a POM, you can use the following:

import org.apache.maven.model.*;
import org.apache.maven.model.io.xpp3.MavenXpp3Writer;
...
Model model = new Model();
model.setGroupId( "some.group.id" );
...
new MavenXpp3Writer().write( w, model );

... where w is a java.io.Writer and you add all the necessary exception handling.

The Javadoc is here: http://maven.apache.org/ref/2.2.1/maven-model/apidocs/index.html

To access this API, you should add this dependency:

<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-model</artifactId>
  <version>2.2.1</version>
</dependency>

There is a corresponding read API as well, but bear in mind that it won't do all the Maven operations such as inheritence and interpolation (to do that requires more advanced API usage).