Tutorials : Handling Messages, Errors and Exceptions in Struts 1.1 :

Looking inside the ActionMessage(s) classes

You've seen how to put data inside the ActionMessage and ActionMessages classes, but it's also possible to pull data out again without having to use the Struts tags. You'd want to do this if you had to write your own tags for displaying messages. Here, first, are the methods you'd have to know from the classes:

You'll also need to know how to find the ActionMessages object. Struts stores it in the request object using the string value "org.apache.struts.action.ACTION_MESSAGE". This value should not be hard coded, but taken from the org.apache.struts.Globals class, which contains most of the keys used for storing various objects. We can also find a pointer to the message resources in the Globals class, and if we want to handle several languages we should also pull out the "locale".

To make it simple here's some code for a jsp-page that peeks into the ActionMessage objects:

Listing 5: The inspectmessages.jsp page

 . .
<%@ page import="java.util.*" %>
<%@ page import="org.apache.struts.*" %>
<%@ page import="org.apache.struts.util.*" %>
<%@ page import="org.apache.struts.action.*" %>

<%
  // Print all attributes in the request object
  out.println("<p><b>All Attributes in request scope:</b>");
  Enumeration paramNames = request.getAttributeNames();
  while (paramNames.hasMoreElements()) {
    String name = (String) paramNames.nextElement();
    Object values = request.getAttribute(name);
    out.println("<br> " + name + ":" + values);
  }
  
  // Print all attributes in the session object
  out.println("<p><b>All Attributes in session scope:</b>");
  paramNames = session.getAttributeNames();
  while (paramNames.hasMoreElements()) {
    String name = (String) paramNames.nextElement();
    Object values = session.getAttribute(name);
    out.println("<br> " + name + ":" + values);
  }

  out.println("<p><b>Data in ActionMessages:</b>");

  // Get the ActionMessages 
  Object o = request.getAttribute(Globals.MESSAGE_KEY);
  if (o != null) {
    ActionMessages ae = (ActionMessages)o;

    // Get the locale and message resources bundle
    Locale locale = 
      (Locale)session.getAttribute(Globals.LOCALE_KEY);
    MessageResources messages = 
      (MessageResources)request.getAttribute
      (Globals.MESSAGES_KEY);

    // Loop thru all the labels in the ActionMessage's  
    for (Iterator i = ae.properties(); i.hasNext();) {
      String property = (String)i.next();
      out.println("<br>property " + property + ": ");

      // Get all messages for this label
      for (Iterator it = ae.get(property); it.hasNext();) {
        ActionMessage a = (ActionMessage)it.next();
        String key = a.getKey();
        Object[] values = a.getValues();
        out.println(" [key=" + key + 
          ", message=" + 
          messages.getMessage(locale,key,values) + 
          "]");
      }
    }
  }
%>
. . .

As you can see, I also print out the objects in the request and session objects. If we have the same data in the ActionMessages object as in Listing 3 we'll get this output from the jsp-page:

The two last lines show the same messages as we got from the code in listing 3. At the top you can also identify the request keys for the ActionMessages object and the message resource bundle.

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