Design Pattern

Core J2EE Patterns

Computer Science

Recursion 
Recursion is the process of repeating items in a self-similar way


For example 7! equals 7*6*5*4*3*2*1 


public int factorial(int n)

{
  if (n <= 1) 
    return 1;
  else
    return n * factorial(n-1);
}

Tail Recursion

Tail call Optimization

Object Oriented Designs

SOLID

S = Single Responsibility Principle
O = Opened Closed Principle 
L = Liscov Substitution Principle
I = Interface Segregation Principle
D = Dependency Inversion Principle

How I explained OOD to my wife

How to select the first/least/max row per group in SQL

How to select the first/least/max row per group in SQL

Seven Security (Mis)Configurations in Java web.xml Files

http://software-security.sans.org/blog/2010/08/11/security-misconfigurations-java-webxml-files

Extract tokens from velocity template

public class MyVariableVisitor extends BaseVisitor

{

public static final String SOURCE_VERSION_ID = "$Id$";

public Object visit(ASTReference arg0, Object arg1)

{

String name = arg0.literal();

List tokenList = (List) arg1;

tokenList.add(name);

return super.visit(arg0, arg1);

}

}

public static void main(String[] args) throws Exception

{

Properties p = new Properties();

p.setProperty("file.resource.loader.path", "D:\\");

VelocityEngine vEngine = new VelocityEngine(p);

Template template = vEngine.getTemplate("just.html");

SimpleNode simpleNode = (SimpleNode) template.getData();

MyVariableVisitor mvVisitor = new MyVariableVisitor();

List tokenList = new ArrayList();

simpleNode.jjtAccept(mvVisitor, tokenList);

for (String item : tokenList)

{

System.out.println(item);

}

}

Ref: http://permalink.gmane.org/gmane.comp.jakarta.velocity.user/14824

Spring tutorial

http://java9s.com/spring-framework/spring-framework-introduction

http://java9s.com/struts-2-mvc/struts-2-mvc-framework-introduction