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Comparing the Struts 1 and Struts 2 Web Application Frameworks

  • November 8, 2007
  • By Michael Klaene
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On to Struts 2...

Now that you've seen Struts 1, it's time to have a second go around at defect-tracker, this time using Struts 2. My goal is to not deviate too much from the original design to to keep comparisons valid. To implement defect-tracker as a Struts 2 application, the first thing you will need to do is modify the web.xml file. Struts 1 used a Java Servlet called ActionServlet to intercept requests matching a specified URI pattern ('*.do' by default). Struts 2 opts to use a Servlet Filter instead. The default extension for Struts 2 is not "*.do" but "*.action". This extension does not need to be specified in the Filter mapping, but will be assumed. It can be overridden, as many of Struts default properties can by editing a 'struts.properties' file and placing it in the classpath. Due to the different ways that each version of Struts maps requests, developers should have no problem using both Struts 1 and Struts 2 together in the same application if they choose.

Filter mappings in Struts 2 web.xml

<filter>
   <filter-name>struts2</filter-name>
   <filter-class>org.apache.struts2.dispatcher.
                 FilterDispatcher</filter-class>
</filter>

<filter-mapping>
   <filter-name>struts2</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>

Struts 1 utilized the 'struts-config.xml' file for Struts configuration. For example, the struts-config is where a developer maps path names to Actions, defines ActionForms that go along with those Actions, and specifies ActionForwards for different types of Action outcomes. Well, a lot has changed in this area in Struts 2. For starters, Struts 2 replaces struts-config with a file called 'struts.xml'. The 'struts.xml' file can be placed anywhere in the classpath. Peering into struts.xml, you will notice some big changes. First and foremost, ActionForms are gone. Struts 2 places no restrictions on where a developer stores a page's data. For example, you can pull the form data directly from the Action class (Actions have stuck around for Struts 2). Struts 2 replaces ActionForward objects with Result objects. Similar to Struts 1, an Action returns a string result that is matched against an entry in struts.xml. Below is how your two Actions in defect-tracker are configured in Struts 2. Note the various changes in element names too. For the most part, these new element names are fairly intuitive of what they represent.

<struts>
<include file="struts-default.xml"/>

<constant name="struts.custom.i18n.resources"
          value="MessageResources" />

<package name="default" extends="struts-default">

   <action name="list" class="web.DefectsList">
      <result>/pages/defects.jsp</result>
   </action>

   <action name="action_*" method="{1}"
           class="web.DefectsAction">
      <result name="input">/pages/editDefect.jsp</result>
      <result type="redirect">list.action</result>
   </action>

</package>

</struts>

In struts.xml, developers group related-actions into a 'package'. You are simply using the default package here. However, if you decided to create a packaged called 'crud' with a similarly titled 'namespace' attribute, URI requests for Actions in that package would take the form of '/crud/*.action'. Developers can define constants here to override some default settings in the Struts 2 framework. Looking at the Action declarations, you will notice that a single result can be specified without a name. Struts 2 assumes this default entry to be the 'success' result and there is no need to specify it. If you will recall, you used a Struts 1 DispatchAction to handle the multiple CRUD events for a defect. There is no need to extend DispatchAction (in fact, DispatchAction does not exist in Struts 2). Rather, a wildcard/placeholding mechanism can be used instead to transfer control to a specific Action method. For example, in the Struts 2 DeffectsAction, a URI of 'action_go' will result in the invocation of a 'go' method on the relevant Action class.

The 'list.action' URI request maps to your Struts 2 version of the DefectsList Action class. Here is the code:

package web;

import business.DefectsManager;
import com.opensymphony.xwork2.ActionSupport;
import java.util.List;

public class DefectsList extends ActionSupport  {

   private List defects;
   private DefectsManager defectsManager;

   public List getDefects() {
      return defects;
   }
   public void setDefects(List defects) {
      this.defects = defects;
   }

   public void setDefectsManager(DefectsManager defectsManager) {
      this.defectsManager = defectsManager;
   }

   public String execute() {
      this.defects = this.defectsManager.getDefects();

      return SUCCESS;
   }

}




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