Multiple session or multi-window problem and solution where multiple class uses a same form extended from SimpleFormController of Spring MVC

Problem:
Lets think of a scenario, we are running a hospital management system. We need to search for patient’s record, doctor’s record, medicine stock record and many other things. Where searching criteria are completely different to each other. In order to implement the OO pattern, we develop a common search class and different command class for different type of search. Following figure illustrates the scenario:

If have created separate bean for Medicine, Doctor and Patient with Search class and define the separate command class for medicine, doctor and Patient. Works fine if you run all these separately. But Open a search page for Doctor then open a search page for Medicine in new window or tab and now press search button for doctor. What happens? You got the search result for Medicine though you suppose to get search result for Doctor.

Observation:
This is one of the most interesting problem of session related task in Spring MVC. Lets go into tail. SimpleFormController of Spring MVC extended from AbstractFromController of spring MVC this contains a method called getFormSessionAttributeName(). The spring framework source code 2.5 returns a string from this method in following way.

protected String getFormSessionAttributeName() {
return getClass().getName() + ".FORM." + getCommandName();
}

This is called 2 times, one while showing the form and one while submitting the form. If your class name is GeneralSearch and package name is net.project.web.search then this method will return the attribute name as net.project.web.search.GeneralSearch.FORM.command. The form kept in session by this name for both searching by different command class of Doctor and Medicine because you have set setSessionForm=true by. Now how do you expect to distinguish both form while submitting it in onSubmit() method? It always replace the old command class by the newest command class thats why in method onSubmit(), out preferred command object is not retrieved accurately.

Solution:
All that we need to do in this case is to make sure the form session attribute name is different for two different command class in our whole search system. You can pass a hidden value
into into your .jsp or .ftl and add it with form session attribute name to make a different session name for each search. You can override the method getFormSessionAttributeName and add the value with the attribute name that is different for each form like following

protected String getFormSessionAttributeName( HttpServletRequest request) {
String sessionId = ServletRequestUtils.getStringParameter( request, "sessionId", null);
if (sessionId!=null) {
return (super.getFormSessionAttributeName(request) + "." +sessionId);
}
return super.getFormSessionAttributeName();
}

You can pass a specific session id as the hidden variable and retrieve it by httpServletRequest and add it with the session attribute name while showing and submitting the form. That will help you to enable to work with multiple session and multi window.

By: Md. Shahjalal