Controlling Duplicate Form Submissions in Struts Applications

How duplicate form submission can be controlled in Struts?

Controlling duplicate form submissions in a Struts application can be achieved through several strategies. Here are some common approaches:

1. Token Mechanism

Struts provides a built-in mechanism for handling duplicate submissions using tokens. You can generate a unique token for each form submission and validate it on the server side.

Steps:

• Generate a token when the form is displayed.
• Include the token in the form as a hidden field.
• On form submission, check if the token is valid and then invalidate it to prevent further submissions.

Example:

// In your Action class
public class MyAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request, HttpServletResponse response) {
        // Check for token
        if (isTokenValid(request)) {
            // Process the form
            resetToken(request); // Invalidate the token
            return mapping.findForward("success");
        } else {
            // Handle duplicate submission
            return mapping.findForward("error");
        }
    }
}

2. Session-based Control

You can store a flag in the session to indicate whether a form has been submitted. If the form is submitted again, you can check this flag and prevent processing.

Example:

public class MyAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request, HttpServletResponse response) {
        HttpSession session = request.getSession();
        Boolean isSubmitted = (Boolean) session.getAttribute("formSubmitted");

        if (isSubmitted != null && isSubmitted) {
            // Handle duplicate submission
            return mapping.findForward("error");
        } else {
            // Process the form
            session.setAttribute("formSubmitted", true);
            return mapping.findForward("success");
        }
    }
}

3. Database Check

Before processing the form submission, you can check the database to see if a similar submission already exists. This is particularly useful for forms that create or update records.

Example:

public class MyAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request, HttpServletResponse response) {
        MyForm myForm = (MyForm) form;
        // Check for existing record in the database
        if (databaseService.exists(myForm.getUniqueField())) {
            // Handle duplicate submission
            return mapping.findForward("error");
        } else {
            // Process the form
            databaseService.save(myForm);
            return mapping.findForward("success");
        }
    }
}

4. JavaScript Prevention

You can use JavaScript to disable the submit button after the first submission. This is a client-side solution and should be combined with server-side checks for better reliability.

Example:

<form action="myAction.do" method="post" onsubmit="this.submitButton.disabled=true;">
    <input type="submit" name="submitButton" value="Submit" />
</form>

5. AJAX Submission

If you are using AJAX for form submission, you can manage the state of the submission on the client side. Once a submission is made, you can disable the form or show a loading indicator to prevent further submissions.

Conclusion

Using a combination of these methods can provide a robust solution to prevent duplicate form submissions in a Struts application. The token mechanism and session-based control are commonly used, while database checks can be useful for ensuring data integrity. Always remember to validate on the server side, as client-side checks can be bypassed.