Why Should You Avoid Returning a ResultSet Directly When Querying a Database?

Returning a ResultSet

When attempting to develop a method that queries a database and retrieves an entire table, it is not recommended to return the ResultSet directly. This can lead to resource leakage and DB resource exhaustion with open connections and statements.

To address this issue, the ResultSet should be mapped to a collection of Javabeans instead, such as an ArrayList. This collection can then be returned by the method.

import java.util.ArrayList;
import java.util.List;
import java.sql.*; // Import necessary sql packages



public class DatabaseOperations {

    public List<Biler> list() throws SQLException {
        List<Biler> bilers = new ArrayList<Biler>(); // Create an ArrayList to store Biler objects

        // Utilizing try-with-resources to automatically close resources
        try (Connection connection = dataSource.getConnection();
             PreparedStatement statement = connection.prepareStatement("SELECT id, name, value FROM Biler");
             ResultSet resultSet = statement.executeQuery()) {

            // Iterate over the ResultSet and create Biler objects
            while (resultSet.next()) {
                Biler biler = new Biler();
                biler.setId(resultSet.getLong("id"));
                biler.setName(resultSet.getString("name"));
                biler.setValue(resultSet.getInt("value"));
                bilers.add(biler);
            }

        } catch (SQLException e) {
            throw new SQLException("An error occurred while retrieving data from the database.", e);
        }

        return bilers;
    }
}

This approach ensures resource safety and allows the caller to access the result set data in a structured manner.

The above is the detailed content of Why Should You Avoid Returning a ResultSet Directly When Querying a Database?. For more information, please follow other related articles on the PHP Chinese website!