title: variables in error messages
body: <p>I have a dropdown box and a TextField. The value of the text field must begin with a unique number depending of the selection. If not an error message will be shown.</p>
  
  <p>Depending on the selection the error message looks like this:</p>
  
  <p>the number in the "TextField" must begin with 101 for selection1</p>
  
  <p>or </p>
  
  <p>the number in the "TextField" must begin with 102 for selection2</p>
  
  <p>etc.</p>
  
  <p>I have written a custom validator to validate the TextField.</p>
  
  <p>What I don't like is that for each error I have a resource key with its corresponding value for the error messages:</p>
  
  <pre><code>@Override
  protected void onValidate(IValidatable&lt;String&gt; validatable) {
  
      if(selection.equals(selections1) &amp;&amp; !beginsWithGoodNumber){
          error(validatable, "error.selection1");
      }else if(selection.equals(selections1) &amp;&amp; !beginsWithGoodNumber){
          error(validatable, "error.selection2");
      }else if(selection.equals(selections1) &amp;&amp; !beginsWithGoodNumber){
          error(validatable, "error.selection3");
      }
  }
  </code></pre>
  
  <p>in the property file I have:</p>
  
  <pre><code>error.selection1 = the number in the '${label}' must begin with 101 for selection1
  error.selection2 = the number in the '${label}' must begin with 102 for selection2
  error.selection3 = the number in the '${label}' must begin with 103 for selection3
  error.selection4 = the number in the '${label}' must begin with 104 for selection4
  </code></pre>
  
  <p>I would like to have something like this in the property file:</p>
  
  <pre><code>error.selection = the number in the '${label}' must begin with {number} for {selection}
  </code></pre>
  
  <p>where <code>{number}</code> and <code>{selection}</code> are variables.</p>
  
  <p>Is this possible?</p>
  
  <p>Thanks.</p>