Develop Reference

Translating logic into Kotlin (or Java) code

I have a use-case where I want to enable users to write simple logic, and behind the scenes, convert this logic into a condition in the code.
For example, the user might write:
someFieldName > 10 AND otherFieldName is NULL
And I'd like that to generate the following code:
if (data["someFieldName"] > 10 && data["otherFieldName"] == null) {
// Do something
}
After doing some research, I saw that one of the options is using eval (by leveraging a JS engine), although it doesn't fit all use cases.
I also saw that it's possible to use tools like ANTLR, which seems a bit like overkill.
Are there any simple off-the-shelf products we can use for such purposes? Or would creating a simple parser ourselves be the best way to handle it?

Your use case can be adequately addressed by MVEL2.
There is no need for you to write a parser and AST with ANTLR or convert to Java code, just evaluate the expression with appropriate parameters.
In fact any Java expression language library would do. You could also look at JUEL.
However, looking at the expression, I would say it aligns more towards MVEL2.
Give both the libraries a try.

Use a SPIN function defined in TopBraid in my Java project

I'm writing my first Java project for Semantic Web using Jena framework.
My ontology was peopled and now I'd like to use some SPIN function (they weren't written by me) in my project.
They are very simple: they receive 2 string arguments and return 1 string.
I never do this kind of project so I don't know from where I can begin.
Can you help me?

The question lacks far too many details, but a wild guess may be that you want to use this in the form:
SELECT *
WHERE {
...
BIND(spin-function(?param1, ?param2) AS ?result)
...
}
That assumes that the Jena framework you are using has SPIN installed.

How to script input for a Java program

I'm writing a Java program that requires its (technical) users to write scripts that it uses as input; it interprets these scripts into a series of actions and executes them. I am currently looking for the cleanest way to implement the script/configuration language. I was originally thinking of heading down the XML route, but the nature of the required input really is a procedural, linear flow of actions that need to be executed:
function move(Block b, Position p) {
// user-defined algorithm for moving block "b" to position "p"
}
Block a = getBlockA();
Position p = getPositionP();
move(a, p);
Etc. Please note: the above is an example only and does not constitute the exact syntax I am looking to achieve. I am still in the "30,000 ft view"-design phase, and don't know what my concreted scripting language will ultimately look like. I only provide this example to show that it is a flow/procedural script that the users must write, and that XML is probably not the best candidate for its implementation.
XML, perfect for hierarchial data, just doesn't feel like the best choice for such an implementation (although I could force it to work if need-be).
Not knowing a lick about DSLs, I've begun to read up on Groovy DSLs and they feel like a perfect match for what I need.
My uderstanding is that I could write, say, a Groovy (I'm stronger in Groovy than Scala, JRuby, etc.) DSL that would allow users to write scripts (.groovy files) that my program could then execute as input at runtime.
Is this correct, or am I misunderstanding the intent of DSLs altogether? If I am mistaken, does anybody have any suggestions for me? And if I am correct then how would a Java program read and execute a .groovy file (in other words, how would my program "consume" their script)?
Edit: I'm beginning to like ANTLR. Although I would love to roll up my sleeves and write a Groovy DSL, I don't want my users to be able to write any old Groovy program they want. I want my own "micro-language" and if users step outside of it I want the interpreter to invalidate the script. It's beginning to seem like Groovy/DSLs aren't the right choice, and maybe ANTLR could be the solution I need...?

I think you are on a really good path. Your users can write their files using your simple DSL and them you can run them by Evaling them at runtime. Your biggest challenge will be helping them to use the API of your DSL correctly. Unless they use an IDE this will be pretty tough.
Equivalent of eval() in Groovy

Yes, you can write a Groovy program that will accept a script as input and execute it. I recently wrote a BASIC DSL/interpreter in this way using groovy :
http://cartesianproduct.wordpress.com/binsic-is-not-sinclair-instruction-code/
(In the end it was more interpreter than DSL but that was to do with a peculiarity of Groovy that likely won't affect you - BASIC insists on UPPER CASE keywords which Groovy finds hard to parse - hence they have to be converted to lower case).
Groovy allows you to extend the script environment in various ways (eg injecting variables into the binding and transferring execution from the current script to a different, dynamically loaded script) which make this relatively simple.

How can I support the SQL GO statement in a Java / jtds application?

I'm working on a Java based OSS app SqlHawk which as one of its features is to run upgrade sql scripts against a server.
Microsoft have made it a convention to split a script into batches with the GO statement, which is a good idea but just asking for false matches on the string.
At the moment I have a very rudimentary:
// split where GO on its own on a line
Pattern batchSplitter = Pattern.compile("^GO", Pattern.MULTILINE);
...
String[] splitSql = batchSplitter.split(definition);
...
which kind of works but is prone to being tripped up by things like quoted GO statements or indentation issues.
I think the only way to make this truly reliable is to have an SQL parser in the app, but I have no idea how to go about this, or whether that might actually end up being less reliable (especially given this tool supports multiple DBMSs).
What ways could I solve this problem? Code examples would be very helpful to me here.
Relevant sqlHawk code on github.
Currently using jtds to execute the batches found in the scripts.

GO is a client batch seperator command. You can replace it with ;. It should not be sent in your EXEC dynamic SQL.
USE master
GO --<----- client actually send the first batch to SQL and wait for a response
SELECT * from sys.databases
GO
Should be translated in
Application.Exec("USE master");
Application.Exec("SELECT * from sys.databases");
or you can write it this way:
Application.Exec("'USE master;SELECT * from sys.databases")
More about GO
http://msdn.microsoft.com/en-us/library/ms188037(v=sql.90).aspx

Ok, so this isn't going to be exactly what you want, but you might find it a start. I released SchemaEngine (which forms the core of most of my products) as open source here. In there, you will find C# code that does what you want very reliably (i.e. not tripping up with strings, comments etc etc). It also support the 'GO x' syntax to repeat a batch x times.
If you download that and have a look in /Atlantis.SchemaEngine/Helpers you'll find a class called BatchParser.cs which contains a method called ParseBatches - which does pretty much what it says on the tin.

Autocomplete functionality for contacts module

I have an application which has a contacts module and I am using JAVA for the same.I have to implement the "Auto complete" functionality for the same. I.e., as i start typing the alphabets, search results start appearing and will eventually narrow down to the matching letter after entering the same.
Please help me with some reference JAVA code, API's and some cool stuffs to go as an add-on.

If you are looking for some example see this
http://viralpatel.net/blogs/2009/06/tutorial-create-autocomplete-feature-with-java-jsp-jquery.html
This one is basic example to make a auto complete.
And if you want some jazzy look and field then you can use jquery plug in client side
http://jqueryui.com/demos/autocomplete/
http://www.devbridge.com/projects/autocomplete/jquery/
http://www.ajaxdaddy.com/demo-jquery-autocomplete.html
I think this will help you.

I think you need to use Ajax for the same . Check out irctc.co.in , they use Ajax for station completion , quite effortlessly