title: Maven - replace java files during project build
body: <p>My question is:
  I have java project and before compilation I need to replace some java files with custom files from external folder.
  I tried build-helper-maven-plugin:</p>
  
  <pre><code>            &lt;plugin&gt;
                  &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
                  &lt;artifactId&gt;build-helper-maven-plugin&lt;/artifactId&gt;
                  &lt;executions&gt;
                      &lt;execution&gt;
                          &lt;id&gt;add-source&lt;/id&gt;
                          &lt;phase&gt;generate-sources&lt;/phase&gt;
                          &lt;goals&gt;
                              &lt;goal&gt;add-source&lt;/goal&gt;
                          &lt;/goals&gt;
                          &lt;configuration&gt;
                              &lt;sources&gt;
                                  &lt;source&gt;custom_scr_directory&lt;/source&gt;
                              &lt;/sources&gt;
                          &lt;/configuration&gt;
                      &lt;/execution&gt;
                  &lt;/executions&gt;
              &lt;/plugin&gt;
  </code></pre>
  
  <p>But is seems that it does not replace files, just add new source folder and that is why I have 'duplicate class' exception during compilation because files have the same names as in the main project.</p>