Spartan Java

Afraid of malicious injections in your web app requests, heres a simple way to improve your application security. Push every request parameter through a filtering function before it’s feeded to your application code.

Such a function can be as simple as:

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private String cleanParameter(String value) {
   if (value != null) {
      value = value.replaceAll("<", "&lt;").replaceAll(">", "&gt;");
      value = value.replaceAll("\\(", "&#40;").replaceAll("\\)", "&#41;");
      value = value.replaceAll("'", "&#39;");
      value = value.replaceAll("eval\\((.*)\\)", "");
      value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\"");
   }
   return value;
}

This will escape/remove potentially dangerous Javascript code and HTML/XML tags.

You can implement this on a web filter or a struts interceptor or a DWR filter depending on the technology you use for you app.

Back in April I wrote about Java to/from JSON serialization using XStream. After developing several AJAX applications using PHP and JQuery, I found that for a lot of scenarios a very simple approach is not only easy but very effective. In the case of PHP, you can effectively enable AJAX in your apps using jQuerys $.getJSON() and PHP json_encode().

I think we can use a very similar approach for Java web applications, enabling the use of AJAX through a very simple, elegant and extensible architecture, without the use of complex frameworks and extra configurations.
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I decided to try out the new Java based version of Google Appengine. So i wrote a very simple web app that allows the user to generate one time passwords (OTP) using the HMAC-SHA1 algortihm (see OATH).

You can check it out at http://obovweb.appspot.com. As the name suggests its based on my obov library.
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The best tool I’ve found so far to serialize POJOs to JSON (and back again) is XStream, it’s automatic, simple and elegant, check it out.

In our first installment we reviewed the front-end part of developing a paginated list using AJAX and Java. Now we will dive into the back-end of our pagination mechanism.
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You have to display a list of items in a web application, for each item allowing several operations (ie modification, deletion, etc.). The list can potentially be quite long, so pagination is required.
This scenario is common in backoffice web applications and public web sites, be it for administering information or as search results display, etc.

I’ll describe a simple way to implement a lightweight pagination engine that minimizes load on the server and gives the user the better experience possible. In this first installment I’ll focus on the front-end side, describing how to lay out the HTML, load it using AJAX and implementing the basic operations the user needs to navigate in your paginated list.
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Using a nice AJAX auto completable input box is much nicer (for the user) than a combo box with 100 options. If you use jQuery, you may use a quite easy yet powerful plug-in called jquery.autocomplete (original, eh?). Grab it at http://www.pengoworks.com/workshop/jquery/autocomplete.htm.
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