How can I avoid running out of memory when creating components dynamically

Question

Hello everyone,
Recently, I am planning to design a web application. It will be used by all middle school teachers in a region to make examination papers and it must contain the following main functions.
1)Generate test questions dynamically. For instance, a teacher who logs on the web application will only see a select one menu and a Next Quiz button. The former is used for determining the number of options for the current multiple/single choice question. The later is dedicated to creating appropriate input text elements according to the selected option number. That is to say, if the teacher selects 4 in the menu and presses the Next Quiz button, 5 input text form elements will appear. The first one is for the question to be asked such as "1.What is the biggest planet in the solar system?", the others are optional answers like a)Uranus. b) Saturn. c)Jupiter. d)Earch. Each answer stands for an input text elements. When the teacher fills in the fourth answer, another select one menu and Next Quiz button will emerge on the fly just under this answer, allowing the teacher to make the second question. The same thing repeats for the following questions.
2)Undo and Redo. Whenever a teacher wants to roll back or redo what he has done, just press the Undo or[i] Redo button. In the previous example, if the teacher selects the third answer and presses the Delete button to drop this answer, it will delete both the literal string content[i] and the input text element, changing the answer d to c automatically. After that, he decides to get back the original answer c, Jupiter, he can just click the Undo button as if he hadn�ft made the deleting operation.
3)Save the unfinished working in the client side. If a teacher has done half of his work, he can choose to press the Save button to store what he has done in his computer. The reason for doing so is simply to alleviate the burden of the server. Although all finished test papers must be saved in a database on the server, sometimes the unfinished papers could be dropped forever or could form the ultimate testing papers after several months. So if these papers keep in the server, it will waste the server computer�fs room. Next time the teacher can press the Restore button on the page to get the previously stored part of the test paper from his own computer and continue to finish the whole paper.
4)Allow at least 1,000 teachers to make test papers at the same time. The maximum question number per examination paper is 60.
Here are my two rough solutions,
A.Using JSF.
B.Using JavaScript and plain JSP[b] without JSF.
The comparison of the two solutions:
1)Both schemas can implement the first and the second requirements. In JSF page I could add a standard panelGird tag and use its binding attribute. In the backing bean, the method specified by the binding attribute is responsible for generating HtmlInput objects and adding them to the HtmlPanelGird object on the fly. Every HtmlInput object is corresponding to a question subject or an optional answer. The method is called by an actionListener, which is registered in the Next Quiz commandButton, triggering by the clicking on this button in the client side. Using JSF can also be prone to managing the HtmlInput objects, e.g. panelGird.getChildren().add(HtmlInput) and panelGird.getChildren().remove(HtmlInput) respond to the undoing operation of deleting an optional answer and the redoing operation of the deleting action respectively. I know JavaScript can also achieve these goals. It could be more complex since I don�ft know well about JavaScript.
2)I can not find a way to meet the third demand right now. I am eager to know your suggestion.
3)Using JSF, I think, can�ft allow 1,000 teachers to do their own papers at the same time. Because in this scenario, suppose each questionnaire having 60 questions and 4 answers per question, there will be approximately 300,000 HtmlInput objects (1,000X60X(4+1)) creating on the server side. The server must run out of memory undoubtedly. To make things better, we can use a custom component which can be rendered as a whole question including its all optional answers. That is to say, a new custom component on the server side stands for a whole question on the client side. Even so, about 60,000(1,000X60) this type of custom components will be created progressively and dynamically, plus other UISelectOne and UICommand objects, it also can�ft afford for most servers. Do I have to use JavaScript to avoid occupying the server's memory in this way? If so, I have to go back and use JavaScript and plain JSP without JSF.
Thank you in advance!
Best Regards, Ailsa
2007/5/4

Answer 1

Thank you for your quick response, BalusC. I really appreciate your answer.
Yes, you are right. If I manually code the same amount of those components in the JSF pages instead of generating them dynamically, the server will still run out of memory. That is to say, JSF pages might not accommodate a great deal of concurrent visiting. If I upgrade the server to just allow 1,000 teachers making their own test papers at the same time, but when over 2,000 students take the same questionnaire simultaneously, the server will need another upgrading. So I have to do what you have told me, using JS+DOM instead of upgrading the server endlessly.
Best Regards, Ailsa