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Home ยป Johannes Brodwal's blog

Thinking Inside a Bigger Box

Welcome to Johannes Brodwall's blog. I use this space to work on articles mostly about software development, with a focus on Java, SOA, and Agile software development. Many of the articles you will find here are not much more than drafts, and I certainly appreciate input on how to make them better.

If you wonder about the title of this blog, Thinking Outside the Box may answer your questions.

I work as the lead software architect of BBS, the company that handles interbank services in Norway. In my copious free time, I develop software and consult companies in development practices and architecture. For more about the services I can offer, please see my resume.

A jQuery inspired server side view model for Java

Submitted by Johannes Brodwal on Tue, 05/07/2013 - 02:33.
 
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In HTML applications, jQuery has changed the way people thing about view rendering. Instead of an input or a text field in the view pulling data into it, the jQuery code pushes data into the view. How could this look in a server side situation like Java?

In this code example, I read an HTML template file from the classpath, set the value of an input field and append more data based on a template (also in the HTML file).

public class ContactServlet extends HttpServlet {
 
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        String nameQuery = req.getParameter("nameQuery");
 
        // Read a pure html template from the classpath
        Xhtml document = Xhtml.fromResource(getClass().getResource("html/contact/index.html"));
 
        // Set the value of the nameQuery input field in the HTML
        document.getForm("#findForm").set("nameQuery", nameQuery);
 
        Element contactsEl = document.select("#contacts");
        Element contactTmpl = contactsEl.take(".contact");
        for (Contact contact : findContacts(nameQuery)) {
            // Fill in the .contact template of the HTML with data
            Element contactHtml = contactTmpl.copy().text(contact.print());
            // And add it to the #contacts element
            contactsEl.add(contactHtml);
        }
 
        document.write(resp.getWriter());
        resp.setContentType("text/html");
    }
}

This is a simplified version of the HTML:

<html>
  <form method='get' id="findForm">
	<input type='text' name='nameQuery' value='null' />
    <input type='submit' name='findContact' value="Find contact" />
  </form>
  <ul id='contacts'>
    <li class='contact'>Johannes (4444444)</li>
  </ul>
</html>

This is a third way from the alternatives of templated views like Velocity and JSP and from component models like JSF. In this model, the view, the model and the binding of the model variables to the view are all separate.

Disclaimer: In this example, I’ve used my still in pre-alpha XML library with the working name of Eaxy. You can get similiar results with libraries like jSoup and JOOX.

Caveat: I’ve never tried this on a grand scale. It’s an idea that compels me for three reasons: First, it’s very explicit. Nothing happens through @annotation, conventions or some special syntax in a template. Second, it’s very unit testable. There is nothing tying this code to running in a web application server. Finally, it’s easy to get to this code through incremental steps. I initially wrote the example application with code that embedded the HTML as strings in Java code and refactored to use the Java Query approach.

Could this approach be worth trying out more?