Java: 2013

Monday 28 October 2013

Developing Restful Web services Using IBM JAX-RS

Java™ API for RESTful Web Services (JAX-RS) is a programming model that provides a mechanism for developing services that follow Representational State Transfer (REST) principles. Using JAX-RS, development of RESTful services is simplified.

The IBM® implementation of JAX-RS provides an implementation of the JAX-RS specification.

IBM JAX-RS includes the following features:

JAX-RS server runtime
Standalone client API with the option to use Apache HttpClient 4.0 as the underlying client
Built-in entity provider support for JSON4J
An Atom JAXB model in addition to Apache Abdera support
Multipart content support
A handler system to integrate user handlers into the processing of requests and responses

Required Jars:

jsr311-api.jar
commons-lang.jar
slf4j-api.jar
slf4j-jdk14.jar
ibm-wink-jaxrs.jar

For Procedure & Detailed description Click Here

Wednesday 23 October 2013

Preventing Browser Back Navigation after Logout - JSPs

Modern Browsers cache the previously visited pages and hence in certain websites where authentication plays an important role, it is necessary to clear them.

The example below illustrates the scenario.

An user logs into his account with credentials.

He navigates between pages within the site.

Once he logs out, the session will terminate but since the browser had cached the previous pages, it is possible for him to click the Back button and see the previously visited pages.

This could possibly breach the security. To avoid this it is necessary to prevent Browser back navigation.

The code given below explains the same scenario.

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
 <%
    session= request.getSession();
    session.setAttribute("username", "login");
 %>
 <form action="login.jsp" method="post">
    Username <input type="text" name="uname"><br/>
    <input type="submit"/>
 </form>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%
   response.setHeader("Cache-Control","no-cache");
   response.setHeader("Cache-Control","no-store");
   response.setHeader("Pragma","no-cache");
   response.setDateHeader ("Expires", 0);

   if(session.getAttribute("username")==null)
      response.sendRedirect("index.jsp");
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
 <%
  String uname = request.getParameter("uname") ;
  session = request.getSession();
  session.setAttribute("username", uname);
 %>
 <h3>Hi <%out.println(uname); %></h3>
 <form action="page1.jsp" method="post">
  Email <input type="text" name="email"/>
  <input type="submit"/>
 </form>
</body>
</html>

page1.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%
   response.setHeader("Cache-Control","no-cache");
   response.setHeader("Cache-Control","no-store");
   response.setHeader("Pragma","no-cache");
   response.setDateHeader ("Expires", 0);

   if(session.getAttribute("username")==null)
      response.sendRedirect("index.jsp");
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>PAGE 1</title>
</head>
<body>
 <%
     String email = request.getParameter("email") ;
 %>
 <h3>Hi <%out.println(email); %></h3>
 <form action="logout.jsp" method="post">
  <input type="submit" value="LOGOUT"/>
 </form>
</body>
</html>

logout.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
    <%
   response.setHeader("Cache-Control","no-cache");
   response.setHeader("Cache-Control","no-store");
   response.setHeader("Pragma","no-cache");
   response.setDateHeader ("Expires", 0);

   session.invalidate();
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>LOGOUT</title>
</head>
<body>
     You have successfully logged out
</body>
</html>

Friday 18 October 2013

Enum in Java

Enum Class for WeekDays

public enum WeekDays {
     MONDAY("M"), TUESDAY("Tu"), WEDNESDAY("W"), THURSDAY("Th"), FRIDAY("F");
 
     private String weekday;
 
     private WeekDays(String s) {
         weekday = s;
     }
 
     public String getWeekday() {
         return weekday;
     }
}

Testing Enum

public class test {
     public static void main(String[] args) {
         System.out.println(WeekDays.FRIDAY.getWeekday());
     }
}

Output

Thursday 17 October 2013

Getting Xml Tag Values using Stack in Java (Applicable to HTML tags) - Parsing

Method Functionality

This method is used to parse the given XML / HTML Entry containing tags.
The values inside the tags are pushed into the Stack.
You can retrieve the values later from the stack by knowing the depth of the Element

Input

<name>Nijin</name>

<city>Chennai</city>

</student>

Output

[Nijin, SSN,Chennai]

Program

public String getValueFromXmlKey(String xmlEntry, int pos){
String value= null;
boolean tagDetected = false;

Stack<String> stack = new Stack<String>();

//Converting String to char Array
char[] xmlEntryArray = xmlEntry.toCharArray();

String elements = "";
for(char c:xmlEntryArray){
if(tagDetected==false){
if(c=='<'){ //Searching for opening tag
tagDetected = true;
if(elements!=""){
stack.push(elements);
}
elements = "";
}
else{
elements += c;
}
}
else{
if(c=='>'){ //Searching for closing tag
tagDetected = false;
}
}
}
System.out.println(stack.get(pos));
return stack.get(pos);
}

Wednesday 16 October 2013

String is immutable in Java

String has a concat(String) method which is used for concatenating.

Illustration
String string1 = "Java";
string1.concat("Programming");
System.out.println(string1);

So, guess what will be string1?

JavaProgramming ??
No!!

Its, still Java
Because Strings are immutable in Java

Sunday 13 October 2013

JDBC-ODBC Connectivity [MS Access]

Procedure
1.Go to Control Panel
2.Click Administrative Tools -- Click Data Sources(ODBC)
3. Now ODBC Data Source Administrator Dialog Box gets opened.
4. Now click System DSN, a dialog box appears and then click Add..
5. Create New Data Source dialog box gets opened and then click Driver Do Microsoft Access (*.mdb) and click Finish.
6. When you click finish, ODBC Microsoft Access Setup gets opened
Fill the following information
Data Source Name: MyDatabase (note:any name, which you will be calling in your program)
Description: <anything>
7. Click Select and locate your mdb file
8. Click OK for all opened dialog boxes. You have successfully created a connection for MS-ACCESS

Oracle Forms Customization

Objective
To create Forms for Banking Application Using Oracle 10g Forms as front end and Oracle 10g as backend.

Table Structure
Table 1.
trans_detrails(trans_id,acc_no,cust_name,acc_type,trans_type,trans_date,trans_amt) where acc_no is account reference,account type=[savings,current],transaction type=[deposit,withdraw]

Table 2.
account(acc_no,balance)

Software Requirements
[1] Oracle Forms 10G
[2] Oracle 10G

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