title: Table using groovy's swing builder
body: <p>Until now I've developed in PHP and JavaScript. I'm currently learning groovy, but unfortunately there aren't many tutorials about this language and the book, I'm currently reading (Groovy Recipes), doesn't contain anything about using groovy's swingbuilder.</p>
  
  <p>As a project at work, I'd like to create a table like the schema bellow:</p>
  
  <pre><code>                                      Instancename 
  
  groupId      artifactId               DEV     TEST   PROD            
  
  firstgroup   firstartifact            1.00    1.05   1.05
  secondgroup  secondartifact           2.02    2.00   2.00
  </code></pre>
  
  <p>That's my current code:</p>
  
  <pre><code>import groovy.swing.SwingBuilder
  import java.awt.BorderLayout
  
  public class Gui {
  
   public void createGui(String instanceTitle, ArrayList&lt;Artifact&gt; columnData){
  
    def bldr = new groovy.swing.SwingBuilder();
  
    def frame = bldr.frame(
     title: "Overview",
     size: [600,150],
     defaultCloseOperation:javax.swing.WindowConstants.EXIT_ON_CLOSE
    ){  
     def tab = table(constraints:BorderLayout.CENTER) {
      tableModel(list:columnData) {
       propertyColumn(header:'GroupId', propertyName:'groupId')
       propertyColumn(header:'ArtifactId', propertyName:'artifactId')
       propertyColumn(header:'Dev', propertyName:'devVersion')
       propertyColumn(header:'Test', propertyName:'testVersion')
       propertyColumn(header:'Prod', propertyName:'prodVersion')
      }
     }
     widget(constraints:BorderLayout.NORTH, tab.tableHeader)
    }
    frame.pack()
    frame.show();
  
    }
  
  }
  </code></pre>
  
  <p>When I run this, I get the table filled with my data. My question is, how can I subordinate "DEV", "TEST" and "PROD" to "Instancename"? I don't know how to add a header above the others.
  In html it would look like this:</p>
  
  <pre><code>&lt;table&gt;
   &lt;tr&gt;
    &lt;td colspan="2"&gt;&lt;/td&gt;
    &lt;td colspan="3"&gt;Instancename&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr&gt;
    &lt;td&gt;groupId&lt;/td&gt;
    &lt;td&gt;artifactId&lt;/td&gt;
    &lt;td&gt;DEV&lt;/td&gt;
    &lt;td&gt;TEST&lt;/td&gt;
    &lt;td&gt;PROD&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr&gt;
    &lt;td&gt;firstgroupid&lt;/td&gt;
    &lt;td&gt;firstartifactid&lt;/td&gt;
    &lt;td&gt;firstdevversion&lt;/td&gt;
    &lt;td&gt;firsttestversion&lt;/td&gt;
    &lt;td&gt;firstprodversion&lt;/td&gt;
   &lt;/tr&gt;
   ...
  &lt;/table&gt;
  </code></pre>
  
  <p>PS: If you know some good groovy tutorials, let me know :)</p>