Helping Java build friendship with Common Lisp

When I was 3rd year student I had functional programming and AI classes where we studied Common Lisp programming language. At the end of AI course I had coursework: write program to calculate differential expression, something like f(x) = x*x then f'(x)=2*x. It was pretty simple to do in Lisp...

As business layer was implemented in Lisp I decided to create user interface in Java. I had to use Swing, because JavaFX didn't exist at this time. So, I guess I started hate Swing from this time...
But here I'd like to show how you can execute Common Lisp from Java (from my personal experience with code sample and some other options). So, how to use Lisp from Java?

Push existing source code to GitHub

There are a lot of advice about that, but the most of them don't work. I found one that really works:

1. Create the remote repository, and get the URL such asgit://github.com/youruser/somename.git
   If your local GIT repo is already set up, skips steps 2 and 3

   ---

2. Locally, at the root directory of your source, git init
3. Locally, add and commit what you want in your initial repo (for everything, git add . git commit -m 'initial commit comment')

   ---

4. to attach your remote repo with the name 'origin' (like cloning would do)
   git remote add origin [URL From Step 1]
5. to push up your master branch (change master to something else for a different branch):
   git push origin master

Origin: http://stackoverflow.com/questions/4658606/import-existing-source-code-to-github

Build fast distributed cache with GoogleGuava

There is a set of application that required distributed cache to work. The classic example is a several front-end servers that share one distributed cache or database engine. And usually you have to sent request each time when you want to get data. 
Depends on your data, the most of request can be used by small part of keys. I mean, for example you have 1M diferent key-value pairs, but you processed usually only 1,000 of them. So, 1% of data makes 99% of requests by keys as on the image:

What u must know about EclipseLink ORM

A year ago I worked with EclipseLink ORM on the project where we're working with Oracle DBMS. I had a strong experience with Hibernate before that.
So, I want to share my experience and compare EclipseLink and Hibernate. Comparison EclipseLink and Hibernate as ORM framweworks for Oracle
Well, I don't like ORM in general, but it often required by management or so on... and in this case, if you have vendor lock in, and this vendor is Oracle, you have to think about EclipseLink as a perfect alternative to Hibernate.

Let's start
EclipseLinks is beter because... It's choosend by Sun Microsystems as standard JPA 2 implementation. It's a better support, bugs are fixed much more quickly; let's look at statistic (as for July 26, 2011):

Name	Number of bugs	Number of blockers	The oldest blocker
Hibernate	156	49	29/Sep/2006
EclipseLink	15	3	04/Jun/2010

It's Oracle-oriented additions which are incredible useful if you create Oracle oriented s/w and want to have all power of oracle in your orm.
The most important Oracle features in EclipseLink are:
1) Built-in Oracle hints support
Hints are important for sql optimization in Oracle and with EclipseLink you can add them through API. Also, EclipseLink will be automatically insert Hints if needs and their usage is clear for orm

2) Hierarchical Queries Support 
PL/SQL has a useful featurs as Hierarchical Queries which can help you a lot if you work with hierarchical structures intensive. So, you don't need to write native sql anymore, just use API

3) Oracle Flashback Transaction Query
 Historical queries during transaction available just from ORM

4) Stored Procedures/Functions Support
Well, Hibernate/JPA also have it. However, in EclipseLink you can use another way (JPA way is still available) with StoredFunctionCall class and related API. In others words, you can build stored procedure/function dynamical invocation. I guess, it is the easiest way to call SP from your java code

Next cool feature is Report Queries that means you can build queries with "reporting" possibilities (AVG, SUM, ROLL UP) with API instead of writing native SQL.

Summarize topic, I can recommend EclipseLink as a perfect ORM for Oracle lock-in project, because a lot of features will be available in this case. However you must keep in mind Hibernate has a lot of own features (versioning, shards, search, etc) and you must to think about your project requirements and pick up the most convenience tool.

H2 vs HSQLDB

There is usual to develop application works with database, often RDBMS. And if you are good developer, you write Unit Tests. As result,  you have to use lightweight rdbms for testing purposes, like H2 or HSQLDB.
So, you can ask yourself what is the right choose? What should you pick up for your project? What is the main difference between hsqldb, h2 and derby?
In the article I'd like to compare H2 and hsqldb and pick up one of them for testing purposes. If you don't have willing to read full article - h2 win.

So, let's start. H2 vs HSQLDB

1) H2 has compatibility mode with Oracle, DB2 and MS SQL as well as with hsqldb, derby, mysql and so on; otherwise it seems poor quality of support, for example I'm not sure, that h2 also support hierarchy queries as Oracle do (needs to check); and it defently doesn't have materialized views. So, this compatible mode is very virtual and limited
2) H2 claims to be faster that hsqldb
3) Hibernate support for hsqldb is more stable, in this point HSQLDB wins, and if you prefer to use Hibernate, you probably must to get hsqldb either h2; also, I have experience of using EclipseLink with h2 and any problems were here
4) as for me, H2 is more easy to use than hsqldb
5) both have views, subqueries, triggers, user defined functions, scrollable result set
6) Indexes available in H2: hash index and full text search
7) h2 is the next project hsdldb's creator :)

Licensing (if you care about it): h2 has mozilla public license and hsqldb has BSD

Also, I've seen XML format support in H2 on several sites, but I've not found detail description or prove link that it's real exist feature

As you understand, it's very simple to switch between these db, usual you have to change connection string if any special functionality is used

Full list of the features of H2 is available here http://www.h2database.com/html/features.html

Also, you can compare both engines and make personal decision:
H2  http://database-management-systems.findthebest.com/l/16/H2
HSQLDB  http://database-management-systems.findthebest.com/l/15/HSQLDB

hadoop jobs waterflow

hi all, sometimes we can solve out task just with one map-reduce job. However we have to create a flow from jobs to solve the most of the real-world tasks. There is simple example, how you can create a flow of tasks. Let's examine the next scheme:

So, we age going to start two M/R jobs at the same time, then cumulate result in third job and pass to 4st. Awesome, let's do it I'll use Google Guava to deals with java collections args - is arguments for job driver, feel free to use Options or whatever

  1 JobControl flow = new JobControl("MR flow");
  2
  3 // we don't have dependencies yet, but API required a list of it
  4 List<ControlledJob> emptyList = Lists.newArrayList();
  5 // and we'll pass this list as dependencies to job C
  6 List<ControlledJob> dependencies = Lists.newArrayList();
  7
  8 ControlledJob aJob = new ControlledJob(getAJob(args), emptyList);
  9 flow.addJob( adJob );
 10 dependencies.add( aJob );
 11
 12 ControlledJob bJob = new ControlledJob(getBJob(args), emptyList);
 13 flow.addJob( bdJob );
 14 dependencies.add( bJob );
 15
 16 ControlledJob cJob = new ControlledJob(getCJob(args), dependencies);
 17 flow.addJob( cJob );
 18
 19 ControlledJob dJob = new ControlledJob(getDJob(args), Lists.newArrayList(cJob));
 20 flow.addJob( dJob );
 21
 22 // hurray! start waterflow!
 23 flow.run();

So, last question to disscusion: what is getXJob misterious methid? In this method we just return configured Job as instance of your Job class. However, any other solution is avaliable hey. Enjoy!

perfect blog about java ee

hi guys, if you have a deals with java ee stuff, soa and other parts of hell... I like to intoduce samolisov.blogspot.com blog (in Russina) There are a lot of useful and up-to-date information about enterprise defelopment and integrations. I believe it will be useful to read for every java ee developer