Refreshing a single component in a JSP page

Question

Can I refresh a HTML component in JSP? I have two dropdowns. On selection of a value in the first dropdown the values in the dropdown box are to be fetched from the database. Is this possible using JSP?

Answer 1

First, JSP is just a view technology which provides a template to write HTML/CSS/JS in and offers facilities to interact with backend Java code using taglibs (like JSTL) and expression language (those ${} things). JSP runs at the server machine, produces a HTML page and sends it to the client side (if you rightclick page and view source in webbrowser, then you should not see any line of Java/JSP code if it has done its work right). JSP does not run at the client machine and can therefore not be directly used to do partial updates in the HTML page.

To achieve what you want, you need to use JavaScript to fire an asynchronous HTTP request (also known as the Ajax technique) to retrieve the data and manipulate the HTML DOM tree accordingly to add the new elements. Since methods to fire Ajax requests and manipulate the HTML DOM may differ among webbrowsers, I strongly recommend to pick the jQuery JavaScript library to keep it concise and simple without any worries about functioning in different webbrowsers.

I've posted an answer in detail about this before, check solution #3 in this answer.