How do I create a batch update in JDBC?

By Wayan in JDBC 0 Comment

A batch statement can be used to execute multiple update commands as single unit in a database manipulation. This statement in the database is not executed one by one but as a single execution instead. In some cases, using a batch update can be more efficient than to execute the commands separately.

In this example, you are shown how to create a batch command to insert some products into a database table.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Arrays;

public class JDBCBatchExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Turn of the auto-commit mode
            connection.setAutoCommit(false);

            try (Statement statement = connection.createStatement()) {
                // And some batch to insert some product information into
                // the product table
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000006', 'Championship Manager')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000007', 'Transport Tycoon Deluxe')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000008', 'Roller Coaster Tycoon 3')");
                statement.addBatch("INSERT INTO product (code, name) " +
                                   "VALUE ('P0000009', 'Pro Evolution Soccer')");

                // To execute a batch command, we must call the executeBatch()
                // method.
                int[] updateCounts = statement.executeBatch();
                System.out.println("updateCounts = " + Arrays.toString(updateCounts));

                // Commit our transaction
                connection.commit();
            } catch (SQLException e) {
                connection.rollback();
                e.printStackTrace();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central

How do I read an applet parameters?

By Wayan in Applet, Core API 0 Comment 
package org.kodejava.applet;

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;

public class AppletParameterExample extends Applet {
    private String name = "";

    public void init() {
        // Here we read a parameter named name from the applet tag definition
        // in our html file.
        name = getParameter("name");
    }

    public void paint(Graphics g) {
        g.setColor(Color.BLUE);
        g.drawString("Hello " + name + ", Welcome to the Applet World.", 0, 0);
    }
}

Now we have the applet code ready. To enable the web browser to execute the applet create the following html page.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Parameterized Applet</title>
</head>
<body>
<applet code="org.kodejava.applet.AppletParameterExample"
        height="150" width="350">
    <param name="name" value="Mr. Bean"/>
</applet>
</body>
</html>
** Deprecated: The Applet API is deprecated since JDK 9, no replacement.

How do I convert string date to long value?

By Wayan in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class StringDateToLong {
    public static void main(String[] args) {
        // Here we have a string date, and we want to covert it to long value
        String today = "25/09/2021";

        // Create a SimpleDateFormat which will be used to convert the string to
        // a date object.
        DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
        try {
            // The SimpleDateFormat parse the string and return a date object.
            // To get the date in long value just call the getTime method of
            // the Date object.
            Date date = formatter.parse(today);
            long dateInLong = date.getTime();

            System.out.println("Date         = " + date);
            System.out.println("Date in Long = " + dateInLong);
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

The result of the code snippet:

Date         = Sat Sep 25 00:00:00 CST 2021
Date in Long = 1632499200000

How do I create a scrollable result sets?

By Wayan in JDBC 0 Comment

Since JDBC 2.0 (JDK 1.2), a scrollable ResultSet was introduced to the java.sql API family. Using this ResultSet enables us to navigate the result set in forward or backward way.

To enable the scrollable ResultSet, we need to create a statement object by defining the ResultSet type (ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.TYPE_SCROLL_INSENSITIVE). If you define the ResultSet type to ResultSet.TYPE_FORWARD_ONLY then you get a regular ResultSet where you can move forward only as in JDBC 1.0

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class ScrollableResultSetExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);

            // This result set is a scrollable result set
            String query = "SELECT * FROM product";
            ResultSet resultSet = statement.executeQuery(query);
            while (resultSet.next()) {
                System.out.println(resultSet.getString("code"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central

How do I move to absolute or relative row?

By Wayan in JDBC 0 Comment

In this example we are showing you how to use result set absolute() and relative() method to jump from one result set row to the other. When you pass a positive number as the parameter, you’ll move from the first record to the last. But if you pass a negative number as parameter, you’ll move from the last record backward.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class MoveAbsoluteOrRelativeExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);

            String sql = "SELECT id, code, name, price FROM product";
            ResultSet rs = statement.executeQuery(sql);

            // Move to the second row
            rs.absolute(2);
            System.out.println("You are now in: " + rs.getRow());

            // Move 2 records forward from the current position 
            // (fourth row)
            rs.relative(2);
            System.out.println("You are now in: " + rs.getRow());

            // Move to the last row in the result set
            rs.absolute(-1);
            System.out.println("You are now in: " + rs.getRow());

            // Move 3 records backward from the current position 
            // (second row)
            rs.relative(-3);
            System.out.println("You are now in: " + rs.getRow());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The code output the following result:

You are now in: 2
You are now in: 4
You are now in: 5
You are now in: 2

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central