Email Validation Using RegularExpression

We can validate Email using regularExpression support given by JDK

  EmailValidation.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class EmailValidation{
     
    public static void main(String args[])
    {
      Pattern pattern;
      Matcher matcher;

String email="suraj20p@gmail.com";
      String EMAIL_PATTERN = "^[_A-Za-z0-9]+(\\.[_A-Za-z0-9]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

   
     //compile our pattern
     pattern = Pattern.compile(EMAIL_PATTERN);
     //pass our email to matcher,so that it can be checked whether pattern is matching or not
     matcher = pattern.matcher(email);
    
     //check whether string is matched or not
      boolean result= matcher.matches();

      if(result)
           System.out.println("Email Validated Successfully");
      else System.out.println("Invalid Email Address");
    }
}

  Download Source Here

Creating a Formatted XML using Java

Lets Assume we want to create an XML file,
Eg:-

CreatXMLFile.java
----------------------
import java.io.*;
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;
import org.w3c.dom.*;
public class CreatXMLFile
{  
public static void main(String[] args) throws Exception
 {   
    //creating factory
    DocumentBuilderFactory documentBuilderFactory =DocumentBuilderFactory.newInstance();
    //creating a builder
    DocumentBuilder documentBuilder =documentBuilderFactory.newDocumentBuilder(); 
    //creating a document
    Document document = documentBuilder.newDocument();
   
    String root = "SMS";

    //adding root Element
    Element rootElement = document.createElement(root);
    rootElement.setAttribute("area", "hyderabad");

    document.appendChild(rootElement); //adds <SMS> as root element

    String element ="Number";    
    String data = "12345";
   
    Element em = document.createElement(element);
    em.appendChild(document.createTextNode(data));
    rootElement.appendChild(em);  //creates <Number>12345</Number> and adds to root element<SMS>
/*
<SMS>
<Number>12345</Number>
</SMS>
*/
  
    element ="message";   
    data= "hello";
  
    em = document.createElement(element);  
    em.appendChild(document.createTextNode(data));
    rootElement.appendChild(em); //creates <message>hello</message> and adds to root element<SMS>
/*
<SMS>
<Number>12345</Number>
<message>hello</message>
</SMS>
*/
  
  
    em=document.createElement("delivered");
    Element childElement = document.createElement("status");
    childElement.appendChild(document.createTextNode("failed"));
    em.appendChild(childElement);
    rootElement.appendChild(em);//creates <delivered><status> failed</status></delivered> and adds to root element<SMS>

 /*<SMS>
<Number>12345</Number>
<message>hello</message>
<delivered>
      <status> failed</status>
</delivered>
</SMS>
    */
   
    //Used to Write the generated xml structure to  file or system console
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    transformer.setOutputProperty(OutputKeys.INDENT, "yes");//arrange the xml in an idented format
    DOMSource source = new DOMSource(document);   
    File f=new File("d:/myfile.xml");
   
    StreamResult result =  new StreamResult(f);  //prints xml into file
    //StreamResult result =  new StreamResult(System.out);   
    transformer.transform(source, result);
 
 }
 }

Adding column to Existing Table

Syntax
alter table <tableName> add  <New_Column> <datatype_with_size>;



SQL>alter table employee add  empsal number(5);

Creating Sequence

A sequence is a variable that can be used to generate unique value everytime


Creating Sequence
CREATE SEQUENCE EMPID_SEQ
 MINVALUE 1
 START WITH 1
 INCREMENT BY 1
 NOCACHE

Calling Sequence
 SELECT EMPID_SEQ.NEXTVAL FROM DUAL;



Dropping Sequence
DROP SEQUENCE EMPID_SEQ

Reading & Writing Data into XLS Sheet

Sometimes we need to read/Write data from/to Excel sheet.
Here  is the way
1.Create one Excel sheet at any Location(Lets say D:\College.xls)
2.Make sure it is not readOnly(otherwise you cannot write data from Java also)
3.Create/Rename a sheet with name "Student"

4.Create ColumnHeading (Normal way) and write some data into it.

5.Create a ODBC DataSource point to the excel file(College.xls)
Navigate to
Start->Control Panel->Administrative Tools->ODBC->"System Dsn" tab->Click on Add Button-->Select "Driver do MS Excel(*.xls)"-->finish

DataSourceName: xlsdsn
 Click on Option button and uncheck  Read Only
Click on select Workbook button and choose D:\College.xls click OK

click ok-->ok
ExcelTest.java

---------------

// ExcelTest.java  (reads/writes the records from/to Ms-Excel sheet)

import java.sql.*;

public class ExcelTest

{
   public static void main(String args[])throws Exception
   {
    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
    Connection    con = DriverManager.getConnection("jdbc:odbc:xlsdsn");

       Statement st = con.createStatement();

       ResultSet rs = st.executeQuery("select * from [student$]");

         while(rs.next()){
              System.out.println(rs.getInt("sno")+"  "+rs.getString("sname")+"  "+rs.getString("sadd"));
         }
         PreparedStatement ps=con.prepareStatement("insert into [student$] values(?,?,?)");
         ps.setInt(1,10);
         ps.setString(2,"Raja");
         ps.setString(3,"ameerpet");
         ps.executeUpdate();
         ps.close();
         rs.close();
         st.close();
         con.close();
     } // main
 } // class 

Download Code Here

Configuring Exception page in web.xml

Instead of showing error page for individual action performed in Servlet,JSP,It is always recommended to configure those error page in web.xml

<web-app>

             <servlet>
                       <!-- some servlet cofiguration -->
             </servlet>

             <servlet-mapping>
                       <!-- some servlet mappings-->
             </servlet-mapping>

            <welcome-file-list>
                         <!-- Welcomefile list configurations-->
            </welcome-file-list>

              <error-page>
                        <error-code>404</error-code>
                        <location>/pagenotfound.jsp</location>
               </error-page>
         
                <error-page>
                         <exception-type>java.lang.Exception</exception-type>
                         <location>/error.jsp</location>
               </error-page>
</web-app>

Knowing the Datatype of a Variable

Given a variable to you,how can u know its type
use typeof operator in javascript

eg:-

alert(typeof "Hello World");
alert(typeof 123);