How to convert an Object into Byte Array

This is a simple program to convert a java object into byte array, This program comes handy when we try to deep clone an object which is my next blog.

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;


/**
 * 
 * @author shailesh.chandra
 *
 */
public class ObjectUtil {

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

  Object object = new Date();

  byte[] byteArray = convertByteArray(object);

  Object readObject = readByteArray(byteArray);

  System.out.println(readObject);

 }

 /**
  * 
  * @param object
  * @return
  * @throws Exception
  */
 private static byte[] convertByteArray(Object object) throws Exception {
  byte[] byteArray;

  ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
  ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
  objectOutputStream.writeObject(object);

  byteArray = byteArrayOutputStream.toByteArray();
  return byteArray;
 }

 /**
  * 
  * @param byteArray
  * @throws IOException
  * @throws Exception
  */
 private static Object readByteArray(byte[] byteArray) throws Exception {
  ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArray);
  ObjectInputStream objectOutputStream = new ObjectInputStream(byteArrayInputStream);
  Object readObject = objectOutputStream.readObject();

  objectOutputStream.close();
  byteArrayInputStream.close();

  return readObject;
 }

}

Deep Clone a object in Java

Below is the simple program to deep clone a object in java

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.Serializable;

/**

 *

 * @author shailesh.chandra

 *

 */

public class DeepCloneExample implements Cloneable, Serializable {

/**

*

*/

private static final long serialVersionUID = 6514927441919765349L;

public static void main(String[] args) throws CloneNotSupportedException {

DeepCloneExample deepCloneExample = new DeepCloneExample();

System.out.println(deepCloneExample);

DeepCloneExample cloneObject = (DeepCloneExample) deepCloneExample.clone();

System.out.println(cloneObject);

}

@Override

protected Object clone() throws CloneNotSupportedException {

Object object = deepClone();

return object;

}

/**

*

* @return

* @throws CloneNotSupportedException

*/

protected Object deepClone() throws CloneNotSupportedException {

DeepCloneExample clone;

try {

clone = null;

ByteArrayOutputStream bytearrayoutputstream = new ByteArrayOutputStream(100);

ObjectOutputStream objectoutputstream = new ObjectOutputStream(bytearrayoutputstream);

objectoutputstream.writeObject(this);

byte abyte0[] = bytearrayoutputstream.toByteArray();

objectoutputstream.close();

ByteArrayInputStream bytearrayinputstream = new ByteArrayInputStream(abyte0);

ObjectInputStream objectinputstream = new ObjectInputStream(bytearrayinputstream);

clone = (DeepCloneExample) objectinputstream.readObject();

objectinputstream.close();

} catch (ClassNotFoundException e) {

e.printStackTrace();

throw new CloneNotSupportedException(e.getMessage());

} catch (IOException e) {

e.printStackTrace();

throw new CloneNotSupportedException(e.getMessage());

}

return clone;

}

}

Using CachedRowSet in Java

Number of times we do not want to maintain a persistent connection while extracting query data from a ResultSet object. The production environment where we want to quickly connect to database extract the result and release the connection. As a developer I always desired if it could be possible to return the ResultSet back to user after closing the connection, but resultset requires a db connection to remain open until processing completes. Wouldn't it be cool to have ability to return a ResultSet object to a different class or thin client without losing the results of a query. Using CachedRowSet we have the one to accomplish same task without complex coding involved.


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import javax.sql.rowset.CachedRowSet;

import com.sun.rowset.CachedRowSetImpl;

/**
 * @author Shailesh Chandra
 *  
 */
public class CachedRowSetExample {

    public static void main(String[] args) throws Exception {
        CachedRowSetExample example = new CachedRowSetExample();
        CachedRowSet cachedRowSet = example.executeQuery();
        while (cachedRowSet.next()) {
            System.out.println(cachedRowSet.getString(1) + "\t" + cachedRowSet.getString(2) + "\t" + cachedRowSet.getString(3));
        }
        cachedRowSet.release();

    }

    public CachedRowSet executeQuery() throws Exception {
        CachedRowSet cachedRowSet = null;
        String query = "select * from TEST1";

        Connection connection = null;
        ResultSet resultSet = null;
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");
            String url = "jdbc:oracle:thin:@server:1521:service_name";
            connection = DriverManager.getConnection(url, "shailesh", "shailesh");
            System.out.println("Connection is " + connection);

            PreparedStatement preparedStatement = connection.prepareStatement(query);
            resultSet = preparedStatement.executeQuery();
            cachedRowSet = new CachedRowSetImpl();
            cachedRowSet.populate(resultSet);

        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {

            if (resultSet != null) {
                System.out.println("Closing resultSet");
                resultSet.close();
            }
            if (connection != null) {
                System.out.println("Closing connection");
                connection.close();
            }

        }
        return cachedRowSet;

    }

}


Displaying an Image from Servlet

package com.shailesh;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ImageServlet extends HttpServlet implements Servlet {
    /**
     * 
     * @see javax.servlet.http.HttpServlet#HttpServlet()
     */
    public ImageServlet() {
        super();
    }

    /**
     * 
     * 
     * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest arg0,
     *      HttpServletResponse arg1)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    /**
     * 
     * 
     * @see javax.servlet.http.HttpServlet#doPost(HttpServletRequest arg0,
     *      HttpServletResponse arg1)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("image/jpeg");
        File file = new File("c:\\myImage.jpg");
        FileInputStream fileInputStream = new FileInputStream(file);
        int i = 0;
        byte[] buffer = new byte[1024];
        while ((i = fileInputStream.read(buffer)) >= 0) {
            response.getOutputStream().write(buffer, 0, i);
        }
    }

}


Sending mail from Java

import java.util.Properties;
import java.util.StringTokenizer;

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class MailSender {
    private static final java.lang.String MAIL_HOST = "mail.smtp.host";
    private Message message = null;
    private Properties props = null;
    private Multipart multipart = null;
    private String host = "";

    public MailSender() {
        String mailHost = ""; //can be read from property file 
        setHost(mailHost);
        initialize();

    }
    /**
     *param string 
     */
    public MailSender(String mailHost) {
        setHost(mailHost);
        initialize();
    }

    /**
     * intializing code 
     *
     */
    private void initialize() {
        props = System.getProperties();
        props.put(MAIL_HOST, getHost());
        Session session123 = Session.getInstance(props, null);
        message = new MimeMessage(session123);
        multipart = new MimeMultipart();
    }

    /**
     * @param string address of SMTP server 
     */
    protected void setHost(String string) {
        host = string;
    }

    /**
     * 
     * @return address of SMTP server being used
     */
    protected String getHost() {
        return host;
    }

    /**
     * 
     * @param address email address of sender 
     * @throws Exception
     */
    public void setFromRecipient(String address) throws Exception {
        message.setFrom(new InternetAddress(address));
    }

    /**
     * 
     * @param address email address of reciever for TO field,
     * if there are more than one reciever this method can be 
     *  used multiple times    
     * @throws Exception
     */
    public void addToRecipient(String address) throws Exception {
        message.addRecipient(
            Message.RecipientType.TO,
            new InternetAddress(address));
    }

    /**
     * 
     * @param address email address of reciever for CC field,
     * if there are more than one reciever this method can be 
     *  used multiple times
     * @throws Exception
     */
    public void addCCRecipient(String address) throws Exception {
        message.addRecipient(
            Message.RecipientType.CC,
            new InternetAddress(address));
    }

    /**
     * 
     * @param address email address of reciever for BCC field,
     * if there are more than one reciever this method can be 
     *  used multiple times
     * @throws Exception
     */
    public void addBCCRecipient(String address) throws Exception {
        message.addRecipient(
            Message.RecipientType.BCC,
            new InternetAddress(address));
    }

    /**
     * 
     * @param subject - subject for the mail
     * @throws Exception
     */
    public void setSubject(String subject) throws Exception {
        message.setSubject(subject);
    }

    /**
     * 
     * @param filename - the name of file to be attached
     * @param filePath - the path of file to be attached
     * @throws Exception
     */
    public void attachFile(String filename, String filePath) throws Exception {

        DataSource source = new FileDataSource(filePath);
        // Set the data handler to the attachment
        BodyPart messageBodyPart = new MimeBodyPart();
        messageBodyPart.setDataHandler(new DataHandler(source));
        // Set the filename
        messageBodyPart.setFileName(filename);
        multipart.addBodyPart(messageBodyPart);
        message.setContent(multipart);
    }

    /**
     * 
     * @param messageText - message content
     * @throws Exception
     */
    public void setMessage(String messageText) throws Exception {
        // Create the message part
        BodyPart messageBodyPart = new MimeBodyPart();
        // Fill the message
        messageBodyPart.setText(messageText);
        multipart.addBodyPart(messageBodyPart);
        message.setContent(multipart);
    }

    /**
     * 
     * @return
     */
    public void sendmail() {
        try {
            Transport.send(message);
            System.out.println("Mail sent successfully");

        } catch (Exception e) {

            e.printStackTrace();
            System.out.println("There was some problem, mail not sent. " + e.getMessage());

        }
    }

    /**
     * 
     * @param argv
     * @throws Exception
     */
    public static void main(String argv[]) throws Exception {

        MailSender mailSender = new MailSender("PUT_SERVER_IP_HERE");
        mailSender.setFromRecipient("I_AM_SENDER@domain.com");

        mailSender.setSubject("How are You?");

        mailSender.addToRecipient("receiver1@domain.com");
        mailSender.addToRecipient("receiver2@domain.co");

        mailSender.addCCRecipient("CCreceiver1@domain.com");
        mailSender.addCCRecipient("CCreceiver2@domain.com");

        mailSender.addBCCRecipient("BCCreceiver1@domain.com");
        mailSender.addBCCRecipient("BCCreceiver2@domain.com");

        mailSender.attachFile("File Name", "FILE PATH");
        mailSender.attachFile("Another File Name", "ANOTHER FILE PATH");

        mailSender.setMessage("Hello, \n\n How are.\n\nThanks.\n");

        mailSender.sendmail();

    }

}