Java User-Agent detector and caching

It’s often important for a server side application to understand the client platform. There are two common methods used for this.

  1. On the client itself, “capabilities” can be tested.
  2. Unfortunately, the server cannot easily test these, and as such must usually rely upon the HTTP Header information, notably “User-Agent”.

Example User-agent might typically look like this for a common desktop browser, developers can usually determine the platform without a lot of work.

"Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)"

Determining robots and mobile platforms, unfortunately is a lot more difficult due to the variations. Libraries as those described below simplify this work as standard Java Objects expose the attributes that are commonly expected.

With Maven, the dependencies are all resolved with the following POM addition:


/* Get an UserAgentStringParser and analyze the requesting client */
final UserAgentStringParser parser = UADetectorServiceFactory.getResourceModuleParser();
final ReadableUserAgent agent = parser.parse(request.getHeader("User-Agent"));

out.append("You're a '");
out.append("' on '");

As indicated on the website documentation, running this query for each request uses valuable server resources, it’s best to cache the responses to minimize the impact!

NOTE: the website caching example is hard to copy-paste, here’s a cleaner copy.

package com.example.cache;

import java.util.concurrent.TimeUnit;
import net.sf.uadetector.ReadableUserAgent;
import net.sf.uadetector.UserAgentStringParser;
import net.sf.uadetector.service.UADetectorServiceFactory;

* Caching User Agent parser
* @see
* @author Scott Fredrickson [skotfred]
* @since 2015jan28
* @version 2015jan28
public final class CachedUserAgentStringParser implements UserAgentStringParser {

private final UserAgentStringParser parser = UADetectorServiceFactory.getCachingAndUpdatingParser();
private static final int CACHE_MAX_SIZE = 100;
private static final int CACHE_MAX_HOURS = 2;
* Limited to 100 elements for 2 hours!
private final Cache<String , ReadableUserAgent> cache = CacheBuilder.newBuilder().maximumSize(CACHE_MAX_SIZE).expireAfterWrite(CACHE_MAX_HOURS, TimeUnit.HOURS).build();

* @return {@code String}
public String getDataVersion() {
return parser.getDataVersion();
* @param userAgentString {@code String}
* @return {@link ReadableUserAgent}
public ReadableUserAgent parse(final String userAgentString) {
ReadableUserAgent result = cache.getIfPresent(userAgentString);
if (result == null) {
result = parser.parse(userAgentString);
cache.put(userAgentString, result);
return result;
public void shutdown() {


Open Source Operating Systems

I’ve posted a lot of information about the common ‘free’ open-source software that I routinely use, however… I just realized that I missed one of the most important applications you use, the Operating System itself.

While my “day job” relegates me to use Windows products for much of my work, I do a lot of additional work at home and for friends.

Currently I use and highly recommend Ubuntu Linux for most users, it’s got most of the usability features of Microsofr Windows and Apple OS/X, but without all of the additional baggage. It’s updated regularly, with new releases every 6 months and software patches made available almost daily. Updates are as non-intrusive as the Windows Update process, and only a very few ever require a reboot.

To quiet the other Linux users out there, I’ve used a lot of Linux ‘flavors’ in the past… each has had it’s place and may do so again…. this is my opinion for the moment and will likely change again in a few years. 🙂

Here’s the list: