Showing posts from November, 2011

Closer to the metal: Clojure, Noir, and plain old Javascript

I am wrapping up a long term engagement over the next five to six weeks that uses Java EE 6 on the backend, and SmartGWT (like GWT, but with very nice commercially supported components) clients. As I have time, I am starting up some new work that uses Clojure and Noir, and it is like a breath of fresh air: I keep a repl open on the lein project and also separately run the web app so any file changes (including the Javascript in the project) are immediately reflected in the app. Such a nice development environment that I don't even think about it while I am working, and maybe that is the point! As I have mentioned in previous blog posts, I really like the Clojure Noir web framework that builds on several other excellent projects. Developing in Noir is a lot like using the Ruby Sinatra framework: handles routes, template support options, but it is largely roll your own environment .

Ruby Sinatra web apps with background work threads

In Java-land, I have often used the pattern of writing a servlet with an init() method that starts up one or more background work threads. Then while my web application is handling HTTP requests the background threads can be doing work like fetching RSS feeds for display in the web app, perform periodic maintenance like flushing old data from a database, etc. This is a simple pattern that is robust and easy to implement with a few extra lines of Java code and an extra servlet definition in a web.xml file. In Ruby-land this pattern is even simpler to implement: require 'rubygems' require 'sinatra' $sum = 0 do # trivial example work thread while true do sleep 0.12 $sum += 1 end end get '/' do "Testing background work thread: sum is #{$sum}" end While the main thread is waiting for HTTP requests the background thread can do any other work. This works fine with Ruby 1.8.7 or any 1.9.*, but I would run this in JRuby for a lon

Using the Stardog RDF datastore from JRuby

I was playing with the latest Stardog release during lunch - the way to quickly get going with the included Java examples is to create a project (I use IntelliJ, but use your favorite Java IDE) and include all JAR files in lib/ (included all nested directories) and the source under examples/src . 6/21/2012 note: I just tried these code snippets with the released version 1.0 of Stardog and the APIs have changed. I took the first Java example class ConnectionAPIExample and converted the RDF loading and query part to JRuby (strange formatting to get it to fit the page width): require 'java' Dir.glob("lib/**.jar").each do |fname| require fname end setupSingletonSecurityManager() com.clarkparsia.stardog.StardogDBMS.get(). createMemory("test") CONN = com.clarkparsia.stardog.api."test").connect() CONN.begin() CONN.add().io().format(

Experimenting with Google Cloud SQL

I received a beta invite today and had some time to read the documentation and start experimenting with it tonight. First, the best thing about Google Cloud SQL: when you create an instance you can specify more than one AppEngine application instances that can use it. This should give developers a lot of flexibility for coordinating multiple deployed applications that are in an application family. I think that this is a big deal! Another interesting thing is that you are allowed some access to the database from outside the AppEngine infrastructure. You are limited to 5 external queries per second but that does offer some coordination with other applications hosted on other platforms or host providers. Their cloud SQL service is free during beta. It will be interesting to see what the cost will be for different SQL instance types. It was very simple getting the example Java app built and deployed. I created a separate SQL instance (these are separate from other deployed AppEng

The quality of new programming languages is apparent by looking at projects using the language

The community growing around the Clojure language is great. While the Clojure platform is still evolving (quickly!) browsing through available libraries, frameworks, and complete projects is amazing. My "latest" favorite Clojure project is Noir that simply provides a composable mechanism for building web applications (using defpartial ). I get to use Noir on two customer web app projects (and some work with HBase + Clojure) over the next month or two, and I am looking forward to that. The simpler of the two web apps is an admin console exposing some APIs on a private LAN and the Try Clojure web app is a great starting point, as well as an example of a nicely laid out Noir application. Since Clojure is such a concise language I find it easy to read through, understand, evaluate, and use projects. Since I am still learning Clojure (I have just used Clojure for about 6 months of paid work over the last couple of years) the time spent reading a lot of available code to find

Writing a simple SQL data source for the free LGPL version of SmartGWT

While travelling back from a vacation I cleaned up some old experimental code for writing a fairly generic SmartGWT data source with the required server side support code. The commercial versions of SmartGWT have support for connecting client side grid and other components to server side databases. For the free version of SmartGWT you have to roll your own and in this post I'll show you a simple way to do this that should get you started. Copy the sample web app that is included in the free LGPL version of SmartGWT and make the modifications listed below. I also set up a Github project that contains everything ready to run in IntelliJ. The goal is to support defining client side grids connected to a database using a simple SQL statement to fetch the required data using a custom class SqlDS . I had to strangely format the following code snippets to get them to fit the content width for my blog: ListGrid listGrid = new ListGrid(); listGrid.setDataSource( new SqlDS

Annoyed by anti-MongoDB post on HN

I am not going to link to this article - no point in giving it more attention. The anonymous post claimed data loss and basic disaster using MongoDB. I call bullshit on this anonymous rant. Why was it posted anonymously? I am sitting in an airport waiting to fly home right now: just finished extending a Java+MongoDB+GWT app and I am starting to do more work on a project using Clojure+Noir+MongoDB. I do have a short checklist for using MongoDB: For each write operation I decide if I can use the default write and forget option or slightly slow down the write operation by checking CommandResult cr = db.getLastError(); - every write operation can be fine tuned based on the cost of losing data. I usually give up a little performance for data robustness unless data can be lost with minimal business cost. I usually use the journalling option. Use replica pairs or a slave. I favor using MongoDB for rapid prototyping and research. I use the right tool for each job. PostgreSQL, variou

Notes on converting an GWT + AppEngine web app using Objectify to a plain GWT + MongoDB web app

There has been a lot of noise in blog-space criticizing Google for the re-pricing of AppEngine services. I don't really agree with a lot of the complaints because it seems fair for Google to charge enough to make AppEngine a long term viable business. That said, I have never done any customer work targeting the AppEngine platform because no one has requested it. (Although I have enthusiastically used AppEngine for some of my own projects and I have written several AppEngine and Wave specific articles.) I still host on AppEngine. I wrote a GWT + AppEngine app for my own use about a year ago, and since I always have at least one EC2 instance running for my own experiments and development work I decided to move my app. It turns out that converting my app is fairly easy using these steps: Copy my IntelliJ project, renaming it and removing AppEngine facets and libraires. Add the MongoDB Java required JARs I had all of my Objectify datastore operations in a si

Recent evaluations of web frameworks while on vacation

My wife Carol and I have been visiting family in Rhode Island this week and since our grandkids are in school on weekdays, I have had a lot of time to spend writing the fourth edition of my Java AI book and also catching up on reevaluating web frameworks. Although my main skill sets are in data/text mining, general artificial intelligence work and Java server side development, I do find myself spending a lot of time also writing web applications. In the last few years, I have done a lot of work with Rails (and some Sinatra), GWT, and most recently with SmartGWT because one of my customers really liked SmartGWT's widgets . (Note: if you are in the San Jose area and want to work on a SmartGWT project with me, please email me!) For my own use, because I have strong Java and Ruby skills, the combination of Rails, GWT, and SmartGWT works very well for me when I need to write a web app. That said, I have spent time this week playing with Google's Closure Javascript tools and l

Anyone know any SmartGWT and Java developers looking for a job?

A call out for some help: one of my favorite customers is looking for a SmartGWT and Java developer in San Jose area - anyone know anyone good + available?