How do I check if a cursor is in the last row?

By I Wayan Saryada in JDBC 0 Comment

On the previous example, we check for the beginning of the result-set. Now using the isAfterLast() method we can check the opposite whether the pointer is at the end of the result set.

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 ScrollableAfterLastExample {
    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 resultSet = statement.executeQuery(sql);

            // Let's jump to the last records. The afterLast() method will
            // position the cursor after the last record.
            resultSet.afterLast();

            while (resultSet.previous()) {
                long id = resultSet.getLong("id");
                String code = resultSet.getString("code");
                String name = resultSet.getString("name");
                double price = resultSet.getDouble("price");

                System.out.println(id + "\t" + code + "\t" + name + "\t" + price);
            }
        } 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 check if a cursor is in the first row?

By I Wayan Saryada in JDBC 0 Comment

When iterating the scrollable result-sets, you can check whether you are in the beginning of the result set or not. The isBeforFirst() method check if the position is at the beginning, if yes this method returns true, otherwise it will return false.

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 ScrollableIsBeforeFirstExample {
    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 resultSet = statement.executeQuery(sql);

            // Using the isBeforeFirst() method we can check if we are at
            // the beginning of the result set.
            if (resultSet.isBeforeFirst()) {
                System.out.println("You are at the beginning of the " +
                                   "result set.");
            }
        } 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 a cursor to the last record?

By I Wayan Saryada in JDBC 0 Comment

To move the cursor to the end of result-set (after the last record), you can call the afterLast() method of the ResultSet.

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 ScrollableAfterLastExample {
    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 code, name, price FROM products";
            ResultSet resultSet = statement.executeQuery(sql);

            // Let's jump to the last records. The afterLast() method will
            // position the cursor after the last record.
            resultSet.afterLast();

            while (resultSet.previous()) {
                String code = resultSet.getString("code");
                String name = resultSet.getString("name");
                double price = resultSet.getDouble("price");

                System.out.println(code + "\t" + name + "\t" + price);
            }
        } 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 a cursor in scrollable ResultSet?

By I Wayan Saryada in JDBC 0 Comment 
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 ScrollableMoveExample {
    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)) {

            // In this example, we first create a statement that allows us
            // to go back and forth in the result-set object. First, we'll
            // iterate the result from beginning to the end.
            Statement statement = connection.createStatement(
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);

            String sql = "SELECT id, code, name, price FROM product";
            ResultSet resultSet = statement.executeQuery(sql);
            while (resultSet.next()) {
                print(resultSet);
            }

            System.out.println();

            // Now the result set pointer is placed after the last record.
            // With the previous method of the result-set, we can now move
            // the pointer backward to the beginning of the result set.
            while (resultSet.previous()) {
                print(resultSet);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static void print(ResultSet resultSet) throws SQLException {
        long id = resultSet.getLong("id");
        String code = resultSet.getString("code");
        String name = resultSet.getString("name");
        double price = resultSet.getDouble("price");

        System.out.println(id + "\t" + code + "\t" + name + "\t" + price);
    }
}

Here are some results of our program.

1   P0000001    Java 2 Notebook 25.0
2   P0000002    Java Servlet Programming    30.0
3   P0000003    PHP Programming 20.0
4   P0000004    Longman Active Study Dictionary 40.0
5   P0000005    Ruby on Rails   24.0

5   P0000005    Ruby on Rails   24.0
4   P0000004    Longman Active Study Dictionary 40.0
3   P0000003    PHP Programming 20.0
2   P0000002    Java Servlet Programming    30.0
1   P0000001    Java 2 Notebook 25.0

Maven Dependencies

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

Maven Central

How do I retrieve values from ResultSet?

By I Wayan Saryada in JDBC 0 Comment

Here is another example on how to read data from a ResultSet returned by executing an SQL query in a database.

We start by creating a connection to the database. Creates a PreparedStatement to execute a query to get some data from the books table.

After executing the PreparedStatement we will have a ResultSet object. To iterate all the data in the ResultSet we call the next() method in a while-loop. When no more record to read the method return false. The ResultSet object also provides some methods to read value of the fields, the name of the method is corresponded to the type of data stored on each field of the table.

To read data using the ResultSet‘s methods (e.g. getString(), getInt(), getFloat(), etc) we can either use the column name, or the column index of the field read in the SQL statement.

Let’s see the complete code snippet below:

package org.kodejava.jdbc;

import java.math.BigDecimal;
import java.sql.*;

public class ResultSetExample {
    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)) {

            String query = """
                    SELECT id,
                        isbn,
                        title,
                        published_year,
                        price
                    FROM book
                    """;

            PreparedStatement ps = connection.prepareStatement(query);
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                // Read values using column name
                Long id = rs.getLong("id");
                String isbn = rs.getString("isbn");
                String title = rs.getString("title");
                int publishedYear = rs.getInt("published_year");

                // Read values using column index
                BigDecimal price = rs.getBigDecimal(5);

                System.out.printf("%s, %s, %s, %d, %.2f\n", id, isbn, title,
                        publishedYear, price);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

As an example, running the code above will give us the following output:

1, 978-1491910771, Head First Java: A Brain-Friendly Guide, 2022, 45.49
2, 978-1617293566, Modern Java in Action, 2019, 54.99

Maven Dependencies

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

Maven Central