Generate ant build file from project issue

Occured in JDeveloper Version: 10.1.3.4

Problem description

Trying to generate ant build file from project issues the following exception in Jdeveloper

java.lang.NullPointerException
    at oracle.ide.net.URLFactory.newURL(URLFactory.java:85)
    at oracle.ide.net.URLFactory.newUniqueURL(URLFactory.java:164)
    at oracle.jdeveloper.builder.SourceModel.generateDefaultFileName(SourceModel.java:135)
    at oracle.jdevimpl.ant.wizard.GenerateBuildfileModel.initializeFromContext(GenerateBuildfileModel.java:83)
    …

Reason

The appropriate project directory is not listed under the Project properties>Project content>Resources.

Solution

Just open the project properties and add the project folder under project content>Resources

After doing so the creation of the ant project build file works as expected!