Programming and Algorithm Tutorial

My previous entry about multi-window or Multiple session shows how we can maintain different session for a same form extended from SimpleFormController of Spring MVC, used by multiple class. Now what about a Form extended from SimpleFormController of Spring MVC opened in different tab or window? A new one will always replace the bean from the session after showing form on showForm() method.

showForm() method of SimpleFormController save the bean in session if setSessionForm(true) for that form just before redering the view. Session works like a HashMap. It saves the bean by a name and this name retrived by calling getFormSessionAttributeName() method. Which is simply the class name(with prefix of package name) + “.Form.command”. So the new bean always replaces the old one in session.

Problem: For example you have a Patient data entry form extended from SimpleFormController of Spring MVC. You want to update two patiend information in two different tab of your browser. You open one form fill up all data and before submit you open another form in another tab. Now the bean in the session will be replaces by this new patient’s information. Now you submit this and get back to previous tab and submit that. onSubmit() method retrive the bean from the session which is the information of the second tab. So you will get incompatible data.

Solution: Soluation is same as the previous entry. You have to override  getFormSessionAttributeName(HttpServletRequest request) method and make sure two name in the session is different. Find a unique identity for two different form. It can be patient id assigned by Hospital or clinic or database index of the patient in storage device. Choosing database index has a problem. Before you submit a new form, you do not know the index so this key is 0(=zero) for a new form.

You can generate a patient id for a new form and keep it as a request attribute and modify session attribute name by overriding getFormSessionAttributeName(HttpServletRequest request) like following code

//to set inrequest:
request.setAttribute("patientId", patientId);
//in getFormSessionAttributeName(HttpServletRequest request) method
@Override
protected String getFormSessionAttributeName(HttpServletRequest request) {
String patientId = (String)request.getAttribute("patientId");
return super.getFormSessionAttributeName()+"."+patientId;
}

So when controller calls getFormSessionAttributeName() it got different session attribute name for two different name and overwrite of bean is prohibited.

by Md. Shahjalal

This entry was posted on Thursday, June 4th, 2009 at 5:16 pm and is filed under Java, Spring. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.