Struts 2 - Creating Dynamic results

Hi everyone,

Today, in this blog post, I am going to jot down a way to create dynamic results in struts 2.

Lets first begin with a few questions.

What do i mean by dynamic results?

We all know that struts allows us to configure the pages to which request must be dispatched to redirected to, via the "result" tag. However, at times, it may be hard to determine at configuration time itself, which pages need to be set as the result. For example, your business logic may determine the action or the jsp that you need to forward to. In the following example, I am going to try and allow the dynamic results in Struts 2.

Whats my objective?

To create an action class that determines the jsp page name that we need to forward to based upon some business logic.

Configure the action in my struts configuration file(struts.xml) for dynamic results

Invoke the action.

Now, lets begin.

Firstly, we create an action class called DummyAction2. (STATUTORY WARNING : The naming conventions in this post, and for the record, many others, might sound bit weird, but i have a tonne of experiments, and its really hard to settle on a proper name for every whim that comes to my mind. So, please bear with me on that note. :> )

My action class is like any other action class. It contains an execute method. But in my case, the execute method does not do anything, except return a "success" string. Thats because i have another business method, which i am going to name as(surprise! surprise!) anotherMethod. This is the method that i am going to invoke using my action mapping.

In order to be able to identify the page that we need to display, we need to create an instance variable that holds the name of the page that we need to forward to. And we create getter/setter methods for this instance variable.

Ill just keep the business logic simple, and store the name of the next page to be displayed, in this instance variable when the action is invoked.

Lets take a sneak peek at the code in the action class.

public class DummyAction2 extends ActionSupport{

    private String nextPage;

    public String execute()
    {
        return ActionSupport.SUCCESS;
    }

    public String anotherMethod(){
        String actionStatus=ActionSupport.INPUT;
        System.out.println("Another Method in Dummy Action");
        
        nextPage = "myPage.jsp";

        actionStatus=ActionSupport.SUCCESS;
        return actionStatus;

    }
    /**
     * @return the nextPage
     */
    public String getNextPage() {
        return nextPage;
    }

    /**
     * @param nextPage the nextPage to set
     */
    public void setNextPage(String nextPage) {
        this.nextPage = nextPage;
    }
}

As you see, there's nothing much going on in my anotherMethod. All i do is to set the value of the next page in the instance variable. And then i simply return a success response from the action class.

The mapping is where the real magic takes place. In your mappings, you can dynamically determine the value of a variable in an action using ordinary EL. Lets see the code first.

                ${nextPage}
            

Okey, i was lying. Its no magic. Its just that, in your struts configuration file, you can access the properties in your current action class using ordinary EL. Thats exactly what we have done here. The string ${nextPage} is used to extract the value of the property named "nextPage" from the current action. And since that action is a jsp page in our case, that's the page that will be rendered to the user.

Invoking the action is done in the same old fashioned way.

Invoke Dynamic Result

I guess, the idea is pretty clear.

Thats all for now. See you folks next time!

Happy Programming :)
Signing Off
Ryan