Here is another example on how to read data from a ResultSet returned by executing an SQL query in database.
package org.kodejava.example.sql;
import java.sql.*;
public class ResultSetExample {
public static void main(String[] args) throws Exception {
Connection connection = getConnection();
try {
String query = "SELECT id, title, publisher, year, price " +
"FROM books";
PreparedStatement ps = connection.prepareStatement(query);
ResultSet rs = ps.executeQuery();
while (rs.next()) {
// Read values using column name
String id = rs.getString("id");
String title = rs.getString("title");
String publisher = rs.getString("publisher");
// Read values using column index
int year = rs.getInt(4);
float price = rs.getFloat(5);
System.out.printf("%s. %s, %s, %d, %f\n", id, title,
publisher, year, price);
}
} finally {
closeConnection(connection);
}
}
private static Connection getConnection() throws Exception {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection("jdbc:mysql://localhost/kodejava",
"kodejava", "kodejava123");
}
private static void closeConnection(Connection connection) {
try {
if (connection != null && !connection.isClosed()) {
connection.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
We start by creating a connection to the database, see the getConnection() method. 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 (eg. getString(), getInt(), getFloat(), etc) we can either use the column name or the column index of the field read in the SQL statement.
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