Java(TM) Boutique - Struts meets Swing (1)

Tutorials : Struts meets Swing (1) :

Returning XML data to the client

This means that the swinglist.jsp page, that returns the list of DVDs to the Swing client, must build an XML representation of the DVDs. Since JDOM has a method that can write the tree-structure to a PrintWriter, we simply catch this output stream in swinglist.jsp and sends it to the Swing client. A new method in the DVDManager is first added:

public void outList(PrintWriter out) {
      XMLOutputter outputter = new XMLOutputter("",false);
      // NB: the outputter does not accept XML headers:  
      outputter.setOmitDeclaration(true); 
      try {
        outputter.output(doc, out);
      } catch (IOException e) {
        e.printStackTrace();
      }    
    }

- Figure 6: The outList method -

This method is then called from swinglist.jsp:

<%@ page language="java" %>
    <%@ page import="java.io.*" %>
    
    <jsp:useBean id="dvds" 
      class="hansen.playground.DVDManager" scope="session"/>
     
    <%
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        dvds.outList(pw); 
        pw.flush();
        out.print(sw.toString());
    %>

- Figure 7: swinglist.jsp -

In a quite similar way we create a swingdetail.jsp page, which will return an XML-file with details for a single (the selected or "current") DVD:

<%@ page language="java" %>
    <%@ page import="java.io.*" %>
    
    <jsp:useBean id="dvds" 
      class="hansen.playground.DVDManager" scope="session"/>
    
    <%
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        dvds.outListElement(pw); 
        pw.flush();
        out.print(sw.toString());
    %>

- Figure 8: swingdetail.jsp -

Instead of using JDOM's XMLOutputter class to build an XML-response we could choose to hand-code the output of the XML. Let me give you an example: If we only wanted to return the titles of the DVDs, we could create a jsp-page like this:

<%@ page language="java" %>
    <%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
    <%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
    
    <jsp:useBean id="dvds" 
      class="hansen.playground.DVDManager" scope="session"/>
    
    <collection>
    <logic:iterate id="dvd" indexId="i" name="dvds" property="dvds">
    <% 
    // Transfer the iteration index to the DVDManager 
    dvds.setIndex(i.intValue()); 
    %>
    <dvd>
    <title><bean:write name="dvds" property="title"/></title>
    </dvd>
    </logic:iterate>
    </collection>

- Figure 9: how to return XML data for the titles -

When this page is invoked it will produce an output like this (blank lines have been removed).

<collection>
      <dvd>
        <title>Amadeus</title>
      </dvd>
      <dvd>
        <title>Lord of the Rings: The Fellowship of the Ring</title>
      </dvd>
      <dvd>
        <title>The Matrix</title>
      </dvd>
    </collection>

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