Ubuntu - linux

Setup ubuntu today.
First impressions:
- Very simple to install (very simple partition manager).
- GUI looks similar to fedora.
- Music started playing without any messy configuration( had to struggle to get it working on fedora)
  Bundled radio stations started singing the melody....
- Was looking around for a cool applications equivalent for ubuntu like "easylife" installer in Fedora.
sudo aptitude install [application name] looks reasonable but not so cool like eaylife.
- Windows XP gets automatically detected and drives get auto mounted.
- More to come..

Useful links:
Linux problem determination
Show all running process

OSGi - Open Services Gateway Initiative

Basics:
Distributed in the form of a bundle.
Ref: http://www.javaworld.com/javaworld/jw-03-2008/jw-03-osgi1.html?page=1


Take it to the server side
An interesting read to start off web app development using osgi with tomcat
http://www.javaworld.com/javaworld/jw-06-2008/jw-06-osgi3.html?page=1

Spring DM (dynamic module) + osgi

Cleanup dirty code using the power of regular expressions

In eclipse search for all irrelevant comments and clean them up:
/\*\s(\r\n.*\r\n)+(\s)+\*.*(@see)*.*(\r\n)+(\s)+\*/
or
For finding all comments blank use >> (?m:)/\*\*(\r\n)+(\s)+\* @[^/]*/
Note: m tells eclipse to search multi line.

Eg:
/*
  *
   * @see ...
   */

The above pattern can be cleaned up very easily with pattern above.

Fun with Typography!!

Want to try out some fonts - use this
A funny vid here[ direct link]

Comic sans is good for non professional usage but it seems to be used in most places(Is it because of microsoft??) : http://bancomicsans.com/home.html

Some sample fonts:

Open Google Serif

Open Google Sans-serif

Open Google Monospace

Open Google Arial

Open Google Comic Sans MS

Open Google Courier New

Open Google Georgia

Open Google Monotype Corsava

Open Google Tahoma

Open Google Times New Roman

Open Google Trebuchet

Open Google Verdana

Behaviour-driven development in Java - Junits evolved ?

As TDD is more of running junits(at a very unit level) and hence we focus very little in writing tests which check code as a functional unit.

BDD(behaviour-driven development) fills up this gap I think and is more closely aligned to developers way of thinking.
I see it more like an organized functional tests in code!

As such system work in unison and not just as a small unit. Hence a boundary has to be defined as to which all parts of the system should be tested and how based on time/money tradeoffs ?

Implementations of BDD for java: http://jbehave.org/
Implementations of BDD for groovy: Easyb

Reference: http://www.jroller.com/DhavalDalal/entry/preferring_bdd_over_tdd

Fast javascript testing

A nice javascript junit test driver to run from eclipse.
http://code.google.com/p/js-test-driver/
http://css.dzone.com/news/fast-javascript-testing

Speed up your maven build

Imagine a company having 10 modules each depending on the other. Lets say building it would take 15 minutes using maven. 
So the team would spend roughly in a day - (noOfBuildTimesPerDay x 15 minutes) x developerCount. This is bad.


Some options :
"mvn clean install" is good for small/medium sized projects but not for bigger ones.

Trade-off between time and space is always there. When space is not a major constraint , we can gain time by

"mvn clean install  -Dmaven.compile.fork=true  -Dmaven.junit.jvmargs=-Xmx512m -Dmaven.junit.fork=true"

With mvn clean, delete on windows is slower, instead if we rename it could boost the build time.
http://bosy.dailydev.org/2009/02/speed-up-your-maven-build-four-times.html

This cut the build time by around 30% on my PC. Thats an improvement isnt it.

I think it would be a big improvement if maven can reuse the classes generated by 
eclipse. Also having an exploded war deployment is an option to reduce pack and unpack times.

Ref:
http://stackoverflow.com/questions/161698/how-can-i-speed-up-my-maven2-build

Real-Time Tracking and Tuning for Busy Tomcat Servers

A very nice article which details on possible options for tomcat server monitoring to tweak its performance.
http://www.devx.com/Java/Article/32730/1954

Free your mind with mindmaps

Mindmaps help you quickly organize and load the knowledge into your brain. Also the noise words are minimal in a mindmap and hence our thinking pattern becomes clearer.

Some usefuls:
For presentation
http://www.mindmeister.com/26036305/presentation-zen-powerful-presentations
for vocabulary
http://www.mindmeister.com/1479825/new-words-oh-a-little-tidy

For a free software goto - freemind.org
online - http://www.mindmeister.com

Eclipse and Idea hot key bindings

Ok our developers use IDEA and Eclipse. And we do pair programming.
Hmmmn I dont want to learn another set of key bindings...!!

Here is the solution:

Using eclipse keys from idea:

• Idea supports Eclipse key binding built-in;
• you just have to switch to eclipse key bindings using preferences dialog;

Using idea key's from eclipse:

• There is a plugin from http://www.jroller.com/santhosh/entry/intellij_idea_key_scheme_for
• I havent tried it as I am an eclipse guy :)..

Tomcat Exploded war - cut deployment time

The time taken for a webapp to be packaged into a war, deploy and then have it unpackaged in tomcat container can be reduced. Simply have the exploded war deployed.  This could save time for developer!!



Steps to make exploded war deployment:

1. add this under pom.xml >> plugins
             
             
                org.codehaus.mojo
                tomcat-maven-plugin
                1.0-beta-1
               
                    admin
                    admin
                    <url>http://localhost:8080/manager
               
                                          


2. mvn war:exploded tomcat:undeploy tomcat:exploded
--This keeps the war exploded, undeploys the webapp context and copies over the exploded build to tomcat using the tomcat manager.


Also a better option to deploy to different servers and also generating the war ( instead of configuration above):
mvn clean install -Dmaven.test.skip=true  war:exploded tomcat:undeploy tomcat:exploded -Dmaven.tomcat.url=http://localhost:8080/manager -Dtomcat.password=admin -Dtomcat.username=admin


Refer for more http://mojo.codehaus.org/tomcat-maven-plugin/exploded-mojo.html

On Java memory - Spaces - Tomcat PermGen errors

Tomcat out of memory: thread
Better Tomcat Manager
Sun doc on java memory spaces

Etags - request header tags to speed up your site .

An ETag (entity tag) is an HTTP response header returned by an HTTP/1.1 compliant web server.

There are 2 possible implementations :
1. Shallow Etag
           - An MD5 hash is computed for first request from the response content and set in the response header by the web filter.For subsequent requests, the filter retreives the previous etag and checks with the new etag computed using the response content.

Minuses:
   -etag is computed after page is rendered on the server.
   - Doesnt work for pages with dynamic content per request (like date/time).
   Spring 3 has this support. It is called ShallowEtagHeaderFilter.

2. Deep Etag
     -This avoids page computation at a much granular level. Uses hibernate interceptors and is not so straightforward to implement. Spring 3 is yet to support this approach.


References:
infoq article

Texter - An auto text expander

I just cant imagine how many times I would have typed the same sentence again and again...

Texter to the rescue.... thanks to Adam Pash!!

As the source is open for viewing, there is no nasty spyware in it I suppose!!

It is built using autohotkey for windows. Its scripting mode is excellent. Check this for syntax.

XSLT caching Transformers

 The usage of cached transformer objects is recommended here

A sample implementation of CachingTransformerFactory is here

The above code abstracts the caching of Transformer objects using HashMap's.

In brief it says to override the TransformerFactoryImpl and cache the transformer objects. The xsl updates are dealt by checking the timestamp on the XSL file.
Hence no need of a web service to update XSL transformer cache!!

Using TransformerFactory.newInstance() ,
there will be absolutely no code change. The Services API will look for a classname in the file META-INF/services/javax.xml.transform.TransformerFactory in jars available to the runtime. More here...

Cron jobs

Cron actually an UNIX tool.

Cron expressions:
* * * * * *
seconds minutes hours "day of month" month "day of week" year

Except year rest all are mandatory.
The details are here

JSP implicit objects printer

copy paste the below and include it using <%@ include file="jspPrinter.jsp" %>

<%@ page
errorPage="ErrorPage.jsp"
import="java.io.*"
import="java.util.*"
%>

<%
Enumeration enames;
Map map;
String title;

// Print the request headers

map = new TreeMap();
enames = request.getHeaderNames();
while (enames.hasMoreElements()) {
String name = (String) enames.nextElement();
String value = request.getHeader(name);
map.put(name, value);
}
out.println(createTable(map, "Request Headers"));

// Print the session attributes

map = new TreeMap();
enames = session.getAttributeNames();
while (enames.hasMoreElements()) {
String name = (String) enames.nextElement();
String value = "" + session.getAttribute(name);
map.put(name, value);
}
out.println(createTable(map, "Session Attributes"));

map = new TreeMap();
enames = request.getAttributeNames();
while (enames.hasMoreElements()) {
String name = (String) enames.nextElement();
String value = "" + session.getAttribute(name);
map.put(name, value);
}
out.println(createTable(map, "Request Attributes"));

%>



<%-- Define a method to create an HTML table --%>

<%!
private static String createTable(Map map, String title)
{
StringBuffer sb = new StringBuffer();

// Generate the header lines

sb.append("");
sb.append("");
sb.append("");
sb.append("");

// Generate the table rows

Iterator imap = map.entrySet().iterator();
while (imap.hasNext()) {
Map.Entry entry = (Map.Entry) imap.next();
String key = (String) entry.getKey();
String value = (String) entry.getValue();
sb.append("");
sb.append("");
sb.append("");
sb.append("");
}

// Generate the footer lines

sb.append("

"); sb.append(title); sb.append("
"); sb.append(key); sb.append("	"); sb.append(value); sb.append("

");

// Return the generated HTML

return sb.toString();
}
%>

Checking websites for malicious content!

These can be done online:

Try:
http://linkscanner.explabs.com/linkscanner/default.aspx
http://www.siteadvisor.com/#

And the name was with DNS

Find out dns server ip address under:

Windows  C:\>ipconfig /all

Linux:  $ cat /etc/resolv.conf

Wildcard DNS: refer this

Wildcard DNS and apache virtual host setup here

Rewrite rules in apache and IIS

Well we can control how the server serves stuff to clients by defining rewrite rules.

As servers are dumb, its important to explain well about the rewrite rules. For example you should explicity say when a rule matches a URL pattern, no need to seek for further rules('L' flag).

The most interesting part is the regular expressions used for rewrite rules. This I will discuss sometime later...But to do some hit and try use me.

Okie, first with apache:
The rewrite rules are handled by module mod_rewrite. This reads the rewrite conf file configured in httpd.conf.

Include the rewrite rule path in httpd.conf >> VirtualHost >>
    Include /path/to/rewrite.conf

Define a rewrite rule file /path/to/rewrite.conf
All set. Ok now the details on rewrite rules:

#This says that rewrite engine is on. This can be configured in httpd.conf as well.
RewriteEngine   On

#for debugging only
RewriteLog logs/rewrite.log
RewriteLogLevel 9

#check if a condition is true:
RewriteCond %{HTTP_HOST} ^local.xyz.com$

#if true above then only apply the below rule(s).
RewriteRule    ^/?$          /journal/index.html [PT]

#RewriteRule    has the syntax RewriteRule
Pattern Substitution [flags]

The important flags are:

L - Stop the rewriting process here and don't apply any more
rewriting rules
R - Redirect. Must have 'L' flag usually with this(to stop processing further)
N - Re-run the rewriting process
P -This flag forces the substitution part to be internally
forced as a proxy request and immediately
NC - No case .This makes the Pattern case-insensitive
PT - pass through to next handler . Works with alias..Used rarely??.

Lots more on Configuration Directives for apache rewrite rules go here:

Gotcha : To apply a rewrite rule based on the request parameter you *have* to use
RewriteCond  %{QUERY_STRING} ^param=value
By default the RewriteRule does not apply for request parameter

On ISAPI rewrite rules for IIS:

Though it is supposed to be a clone of apache mod_rewrite to help IIS do the redirections there are some differences. There are more ISAPI_Rewrite directives for IIS like RewriteHeader ,etc
More or less the syntax match (thank god) and should be easy if u know apache rewrites.

More on IIS rewrite rules here