TOTD #5: Loading data from beans in jMaki widgets

The
jMaki
tutorial from SWDP explained the different approaches to load your own data
into a jMaki widget. The jMaki widget models have

formalized since then and so the code there no longer works. This TOTD
explains how a combo box widget in a JSP page gets it data from a bean.

This TOTD uses NetBeans IDE configured with
jMaki plugin and
GlassFish.

1. Create a new Web application project using
   NetBeans IDE, enable "jMaki Framework" and use all the
   defaults. Choose GlassFish as the "Server".
2. In the default generated "index.jsp" page, drag-and-drop "

   Dojo 
   	Combobox

   " in the "Main Content Area".
3. Replace the generated code with the following fragment
   
   
   
   

   <jsp:useBean id="itemBean" scope="session" class="server.ItemValueBean" 
   	/&gt;<br>
   	&lt;a:widget name=&quot;dojo.combobox&quot; value=&quot;${itemBean.value}&quot;/&gt;<br>
   	

   
   
   jsp:useBean tag instantiates the bean "server.ItemValueBean"
   in session scope. a:widget tag uses ${itemBean.value}
   expression to load the data by invoking getValue() method from
   the bean.
4. Add a new class to the project and name it "ItemValueBean"
   in the package "server". Replace the entire generated code with
   the following:
   
   
   
   

   package server;<br>
   	<br>
   	import org.json.JSONArray;<br>
   	import org.json.JSONException;<br>
   	import org.json.JSONObject;

   public class ItemValueBean {<br>
   &nbsp; public String getValue() {<br>
   &nbsp;&nbsp;&nbsp; JSONArray value = new JSONArray();<br>
   &nbsp;&nbsp;&nbsp; for (int i=0; i&lt;2; i++) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; try {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; JSONObject item = new JSONObject();<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; item.put(&quot;name&quot;, &quot;name&quot; + i);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; item.put(&quot;label&quot;, &quot;label&quot; + i);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value.put(item);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } catch (JSONException ex) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ex.printStackTrace();<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp; }<br>
   	<br>
   &nbsp;&nbsp;&nbsp; try {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return jsonArrayToString(value, null);<br>
   &nbsp;&nbsp;&nbsp; } catch (JSONException ex) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ex.printStackTrace();<br>
   &nbsp;&nbsp;&nbsp; }<br>
   	<br>
   &nbsp;&nbsp;&nbsp; return null;<br>
   &nbsp; }<br>
   	<br>
   &nbsp; /**<br>
   &nbsp; * Converts a JSON Object to an Object Literal<br>
   &nbsp; *<br>
   &nbsp; */<br>
   &nbsp; public String jsonToObjectLibertal(JSONObject jo, StringBuffer buff) 
   	throws JSONException {<br>
   &nbsp;&nbsp;&nbsp; if (buff == null)<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff = new StringBuffer(&quot;{&quot;);<br>
   &nbsp;&nbsp;&nbsp; else <br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(&quot;{&quot;);<br>
   &nbsp;&nbsp;&nbsp; JSONArray names = jo.names();<br>
   &nbsp;&nbsp;&nbsp; for (int l=0; (names != null) &amp;&amp; l &lt; names.length(); l++) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; String key = names.getString(l);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; String value = null;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (jo.optJSONObject(key) != null) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   	jsonToObjectLibertal(jo.optJSONObject(key), buff);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (jo.optJSONArray(key) != null) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; jsonArrayToString(jo.optJSONArray(key), 
   	buff);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (jo.optLong(key, -1) != -1) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot; + jo.get(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (jo.optDouble(key, -1) != -1) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot; + jo.get(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (jo.opt(key) != null) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Object obj = jo.opt(key);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (obj instanceof Boolean) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot; + 
   	jo.getBoolean(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = key + &quot;:&quot; + &quot;'&quot; + 
   	jo.get(key) + &quot;'&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (l &lt; names.length() -1) buff.append(&quot;,&quot;);<br>
   &nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp; buff.append(&quot;}&quot;);<br>
   &nbsp;&nbsp;&nbsp; return buff.toString();<br>
   &nbsp; }<br>
   &nbsp; <br>
   &nbsp; public String jsonArrayToString(JSONArray ja, StringBuffer buff) throws 
   	JSONException {<br>
   &nbsp;&nbsp;&nbsp; if (buff == null)<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff = new StringBuffer(&quot;[&quot;);<br>
   &nbsp;&nbsp;&nbsp; else<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(&quot;[&quot;);<br>
   	<br>
   &nbsp;&nbsp;&nbsp; for (int key=0; (ja != null) &amp;&amp; key &lt; ja.length(); key++) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; String value = null;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (ja.optJSONObject(key) != null){<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
   	jsonToObjectLibertal(ja.optJSONObject(key), buff);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (ja.optJSONArray(key) != null) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; jsonArrayToString(ja.optJSONArray(key), 
   	buff);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (ja.optLong(key, -1) != -1) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = ja.get(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (ja.optDouble(key, -1) != -1) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = ja.get(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (ja.optBoolean(key)) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = ja.getBoolean(key) + &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else if (ja.opt(key) != null) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Object obj = ja.opt(key);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (obj instanceof Boolean) {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = ja.getBoolean(key) 
   	+ &quot;&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else {<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; value = &quot;'&quot; + ja.get(key) 
   	+ &quot;'&quot;;<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; buff.append(value);<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (key &lt; ja.length() -1) buff.append(&quot;,&quot;);<br>
   &nbsp;&nbsp;&nbsp; }<br>
   &nbsp;&nbsp;&nbsp; buff.append(&quot;]&quot;);<br>
   &nbsp;&nbsp;&nbsp; return buff.toString();<br>
   &nbsp; }<br>
   	}<br>
   	<br>
   	

   The getValue methods contains the logic to generate the
   business data. In this case, the method generates the
   data model
   expected by ComboBox using
   JSON APIs. This data can very well be generated by
   creating a
   Persistence Unit and querying a database using JPA or any other
   mechanism.
   
   
   
   The jsonToObjectLibertal and jsonArrayToString
   methods were originally posted
   here.
   These two methods are required because the JSON parser does not allow you to
   create object literals but only JSON objects. By default these contain key :
   value pairs where the keys are enclosed in double quotes which does not
   match with the expected data model.
5. Deploy and Run the application. The browser windows shows the default
   page with a drop-down list box. The expanded list box shows the items that
   are added to the combo box.
   
   
   
   
   
    

Another way to populate jMaki widgets with your data (using JPA) is explained

here.

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