servlet – Data Science, Data Analytics and Machine Learning Consulting in Koblenz Germany

GWT + database connection in Servlet ContextListener – Auto Complete Video Tutorial Part 5

Rene — Mon, 24 Jun 2013 11:44:47 +0000

Finally we have all the basics that are needed for building an Autocomplete service and now comes the juicy part. From now on we are looking at how to make it fast and robust. In the current approach we open a new Data base connection for every HTTP request. This needs quite some time to lock the data base (at least when using neo4j in the embedded mode) and then also to run the query without having any opportunities to use the caching strategy of the data base.
In this tutorial I will introduce you to the concept of a ContextListener. This is roughly spoken a way of storing objects in the Java Servlet global memory using key value pairs. Once we understand this the roadmap is very clear. We can store objects like data base connections or search indices in the memory of our web server. As from what I currently understand this could also be used to implement some server side caching. I did not do any benchmarking yet testing how fast retrieving objects from context works in tomcat. Also this method of caching does not scale horizontally well as using memcached.
Anyway have fun learning about the context listener.

If you have any suggestions, comments or thoughts or even know of some solid benchmarks about caching using the ServletContext (I did a quick web search for a view minutes and didn’t find any) feel free to contact me and discuss this!

Building an Autocomplete Service in GWT screencast Part 4: Integrating the neo4j Data base

Rene — Thu, 20 Jun 2013 12:38:46 +0000

In this screencast of my series I explain at a very basic level how to integrate a data base to pull data for autocomplete queries. Since we have been working with neo4j at this time I used a neo4j data base. It will be only in the next two parts of this series where I introduce an efficient way of handling the data base (using the context listener of the web server) and building fast indices. So in this lesson the resulting auto complete service will be really slow and impractical to use but I am sure for didactic reasons it is ok to invest 7 minutes for a rather bad design.
Anyway if you want to use the same data set as I used in this screencast you can go to http://data.related-work.net and find the data set as well as a description of the data base schema:

Building an Autocomplete Service in GWT screencast Part 3: Getting the Server code to send a basic response

Rene — Mon, 17 Jun 2013 12:20:11 +0000

In this screencast of my series on building an autocomplete service you will learn how to implement a Server servlet in GWT such that autocomplete queries receive a response. In this video the response will always be static and very naive. It will be up to the fourth part of this series which will follow already this week to make the server to something meaningful with the query. This part is rather created to see how the server is supposed to be invoked and what kind of tools and classes are needed. So see this as a preparation for the really interesting stuff.

If you have any questions, suggestions and comments feel free to discuss them.