Saturday, February 9th, 2008
If you have been developing Struts2 applications in version <= 2.0.9, there are two important compatibility issues that you must address before you can upgrade to 2.0.11 or 2.1. These are the portlet compatibility issues and EL expression issue in Struts2 tags.
1. Struts 2.0.9 contained a major security issue as detailed here. The problem was that using EL expressions and OGNL tags at the same time in Struts2 tags, malicious code could be executed. The fix in 2.0.11 was to disable EL expressions completely(!). This means that code written in 2.0.9 will break in 2.0.11 if you have used EL expressions in JSP. If you have a well tested production system, this means total nightmare. Well, now you are between devil and the sea! 
2. Portlet support is undergoing drastic changes. If you have already developed your portlet application in 2.0.9, you will have to do a couple of changes before you can move to 2.0.11 or 2.1. This includes changes in web.xml.
Posted in Migrating, Struts 2.0.11 | No Comments »
Wednesday, January 16th, 2008
Download Source | View Demo
Important : This example uses Struts 2.0.11. Struts2 Ajax support is experimental is undergoing rapid changes. I will update this example once Struts 2.1 is released.
One of the biggest improvements in Struts2 compared to Struts is its first class AJAX support. All the core Struts2 components are developed with a view of deploying in a highly responsive AJAX mode. In this post, I will look at the Struts2 div tag which can be used to render Ajax content. This component internally uses Dojo library for Ajax functionality.
To demonstrate this, I will create a very simple use case. The use case consists of a single screen which lists a number of users in a table. When a userid link is clicked, user details is shown at the bottom. For displaying user details we will use Ajax.
Following are the files used in this sample Struts2 project. The code listing is also given below.
1. web.xml
J2EE configuration file
2. struts.xml
Mvc configuration for struts
3. userlisting.jsp
4. userdetail.jsp
This displays user details and is loaded using Ajax from userlisting.jsp
5. UserListingAction.java (under package ajaxdemo/action)
Prepares data for user listing and dispatches to userlisting.jsp. In a real application, this will connect to datasource through a business layer.
6. UserDetailAction.java (under package ajaxdemo/action)
This loads the data when a userid is selected in userlisting.jsp. This is called via Dojo Ajax.
7. UserListDTO.java (under package ajaxdemo/dto
This encapsulates details of a single user displayed in the list. Contains id and name. DTO stands for Data Transfer Object.
8. UserDetailDTO.java (unser package ajaxdemo/dto)
This encapsulates the complete details of a specific user.
When you access the URL http://localhost:8084/ajaxdemo/UserListingAction.action, UserListingAction prepares the data and it forwards to the userlisting.jsp. For Ajax, we use div tag in Struts2 tag library. Whenever a userid is clicked in the list, JavaScript function notifies the div tag to dynamically load content from a URL. In this case it is UserDetailAction which in turn gets data corresponding to the selected userid and dispatches to userdetail.jsp. The content returned by userdetail.jsp is loaded under Struts div tag.
As you can see the entire Ajax plumbing is hidden from the application developer and it is possible to quickly build highly responsive Web applications using this simple technique.
This sample application is hosted here. Check out to see the beauty of Struts2 Ajax. You can also download the entire source as a war file.
Note: We don’t want the user details to be loaded initially. But as of Struts 2.0.11, it is not possible to prevent the initial Ajax call. It seems that Struts 2.1 has introduced an attribute “preload” for preventing initial Ajax load. The work around here is to check the userid before returning any content.
In the next part we will look at each of the files in detail.
Posted in Ajax, Struts 2.0.11, Tutorials | 3 Comments »