Generating Portlet URLs

Developing Your First Portlet
Step 3 of 8

Recall that users can place multiple portlets on a single page. As a developer, you have no idea what other portlets will share a page with yours. This means that you can’t define URLs for various functions in your application like you may be used to.

For example, consider a Calendar application that a user puts on the same page as a Blog application. To implement the functionality for deleting calendar events and blog entries in the respective application, both application developers append the del parameter to the URL, and give it a primary key value so the application can look up and delete the calendar event or blog entry. Since both applications read this parameter, their delete functionality clashes.

System-generated URLs are Liferay DXP’s solution to this. By generating a unique URL parameter for each piece of functionality, Liferay DXP lets multiple applications with the same or similar functionality coexist in perfect harmony. Unfortunately, for this to work in your portlet you must manually add support for it. Fortunately, doing so is very straightforward.

In view.jsp, follow these steps to enable system-generated URLs in your portlet:

1. Add these tags below <%@ include file="/init.jsp" %>, but above the <aui:button-row> tag:

   <portlet:renderURL var="addEntryURL">
       <portlet:param name="mvcPath" value="/edit_entry.jsp"></portlet:param>
   </portlet:renderURL>
   

2. Add this attribute to the <aui:button> tag, before value="Add Entry":

   onClick="<%= addEntryURL.toString() %>"
   

   Your view.jsp page should now look like this:

   <%@ include file="/init.jsp" %>
   
   <portlet:renderURL var="addEntryURL">
       <portlet:param name="mvcPath" value="/edit_entry.jsp"></portlet:param>
   </portlet:renderURL>
   
   <aui:button-row>
       <aui:button onClick="<%= addEntryURL.toString() %>" value="Add Entry"></aui:button>
   </aui:button-row>
   

The <portlet:renderURL> tag’s var attribute creates the addEntryURL variable to hold the system-generated URL. The <portlet:param> tag defines a URL parameter to append to the URL. In this example, a URL parameter named mvcPath with a value of /edit_entry is appended to the URL.

Note that your GuestbookPortlet class (located in your guestbook-web module’s com.liferay.docs.guestbook.portlet package) extends Liferay’s MVCPortlet class. In a Liferay MVC portlet, the mvcPath URL parameter indicates a page within your portlet. To navigate to another page in your portlet, use a portal URL with the parameter mvcPath to link to the specific page.

In the example above, you created a renderURL that points to your application’s edit_entry.jsp page, which you haven’t yet created. Note that using an AlloyUI button to follow the generated URL isn’t required. You can use any HTML construct that contains a link. Users can click your button to access your application’s edit_entry.jsp page. This currently produces an error since no edit_entry.jsp exists yet. Creating edit_entry.jsp is your next step.