Liferay Portal server provides the mechanism to create the multiple instances of a portlet. Its a common requirement to display different contents/data in each instance of the portlet.
For example, the following snapshot shows a portlet with 3 instances. Each instance display the different data. The first display the used memory of the JVM, next shows the Free memory and the last shows the Current Sales.
As the multiple instances of the portlet are similar but display the different data, it make sense to develop only a single portlet and create the multiple instances. This blog explains a method to achieve it.
First create a new "Liferay Project" using the eclipse wizard and select the "Allow Multiple Instances" to enable the multiple instances of the portlet, also select the "Edit Mode" of the Portlet Mode option as we would like to configure the Portlet instances from preferences option. It allows the administrator to configure the portlet instances and specify the content to display in the instance. The users without the "configuration" privileges would not be able to change the settings, and view the configured instances.
The Preferences option allows the administrator to specify the content to view in the instance. Choose the Preferences option and..
.. the following is displayed, to provide the content to display in this instance. Please provide the name as follows and save it.
The Portlet Preferences is used in the edit.jsp page to store the preferences of the instance of the portlet. Please see the following edit.jsp source code for details.
<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet"%>
<%@ taglib uri="http://liferay.com/tld/aui" prefix="aui"%>
<%@ page import="javax.portlet.PortletPreferences"%>
<portlet:defineObjects />
Please provide the name of the portlet to view in
<b>MultiInstancePortlet</b>
.
<%
PortletPreferences prefs = renderRequest.getPreferences();
String content = renderRequest
.getParameter("<portlet:namespace/>content");
if (content != null) {
prefs.setValue("content", content);
prefs.store();
%>
<p>Saved Successfully!!</p>
<%
} else {
content = (String) prefs.getValue("content", "");
}
%>
<portlet:renderURL var="editURL">
</portlet:renderURL>
<aui:form action="<%=editURL%>" method="post">
<aui:input label="Content" name="<portlet:namespace/>content"
type="text" value="<%=content%>" />
<aui:button type="submit" />
</aui:form>
The view.jsp is similar to the previous
blog for Ajax processing using jQuery.
<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet"%>
<portlet:defineObjects />
<portlet:resourceURL var="resourceURL">
</portlet:resourceURL>
<script type="text/javascript">
function <portlet:namespace/>Data(){
$.post("<%=resourceURL%>", function(result) {
if (result == 'NOT_CONFIGURED') {
$('#<portlet:namespace/>header')
.text('Portlet not configured!');
return;
}
var vals = result.split(',');
$('#<portlet:namespace/>container').css('width', vals[1] + '%');
$('#<portlet:namespace/>value').text(vals[1] + '%');
$('#<portlet:namespace/>header').text(vals[0]);
});//post
}
$(document).ready(function() {
setInterval("<portlet:namespace/>Data()", 1000);
});
</script>
<div id="<portlet:namespace/>header"
style="color: orange; font-size: 18px;">JVM Used Memory -</div>
<br />
<h4 id="<portlet:namespace/>value">--</h4>
<div style="border: 1px solid Blue; width: 100%; height: 5px;">
<div id="<portlet:namespace/>container"
style="background-color: SkyBlue; width: 0px; height: 5px;"></div>
</div>
Finally, for backend processing the following MultiInstancePortlet.java class implements the serveResource method invoked during the POST method invocation. It checks the value of "content" in PortletPreferences of the instance and sends the data for that particular "content" type.
package com.test;
import java.io.IOException;
import java.io.PrintWriter;
import javax.portlet.PortletException;
import javax.portlet.PortletPreferences;
import javax.portlet.ResourceRequest;
import javax.portlet.ResourceResponse;
import com.liferay.util.bridges.mvc.MVCPortlet;
/**
* Portlet implementation class MultiInstancePortlet
*/
public class MultiInstancePortlet extends MVCPortlet {
@Override
public void serveResource(ResourceRequest resourceRequest,
ResourceResponse resourceResponse) throws IOException,
PortletException {
System.out.println("serveResource..");
long freemem = Runtime.getRuntime().freeMemory();
long totalmem = Runtime.getRuntime().totalMemory();
long usedmem = totalmem - freemem;
usedmem = usedmem / (1024 * 1024);// MB
freemem = freemem / (1024 * 1024);//MB
totalmem = totalmem / (1024 * 1024);// MB
PortletPreferences prefs = resourceRequest.getPreferences();
String content = prefs.getValue("content", "");
PrintWriter writer = resourceResponse.getWriter();
if(content.equals("JVM Used Memory")){
long percentage = usedmem * 100 / totalmem;
writer.print(content+ " - "+usedmem + "/" + totalmem + " MB," + percentage);
}else if(content.equals("JVM Free Memory")){
long percentage = freemem * 100 / totalmem;
writer.print(content+ " - "+freemem + "/" + totalmem + " MB," + percentage);
}else if(content.equals("Current Sales")){
long peakSale = 1000;
long currentSale = (long) (peakSale * Math.random());
long percentage = currentSale * 100 / peakSale;
writer.print(content+ " - "+currentSale + "/" + peakSale + " Units," + percentage);
}else if(content.equals("")) {
writer.print("NOT_CONFIGURED");
}
writer.close();
}
}
Please note that for simplicity, this example shows a very basic mechanism for contents type matching but it could be configurable in some database.
