RDS.java

import java.sql.*;

public class RDS {
    private static final String DEFAULT_USER = "test";
    private static final String DEFAULT_PW = "test";

    /**
     * Simple connection to test for demo purpose
     * Connects to an existing Postgres Database, creates a table, inserts some dummy data, and selects the data afterwards.
     *
     * @param hostname name of the database host
     * @param port port
     * @param dbname database name
     * @return String with the result of the select query
     *
     * @throws SQLException
     * @throws ClassNotFoundException
     */
    protected static String test_connection(String hostname, Integer port, String dbname) throws SQLException, ClassNotFoundException {
        Connection c = null;

        try {
            Class.forName("org.postgresql.Driver");
            String url = String.format("jdbc:postgresql://%s:%d/%s", hostname, port, dbname);
            c = DriverManager.getConnection(url, DEFAULT_USER, DEFAULT_PW);
            c.setAutoCommit(true);
            try (Statement stmt = c.createStatement()) {
                String sql = "CREATE TABLE HELLO " +
                        "(ID INT PRIMARY KEY     NOT NULL," +
                        " NAME           TEXT    NOT NULL) ";
                stmt.executeUpdate(sql);

                sql = "INSERT INTO HELLO (ID,NAME) VALUES (1, 'world');";
                stmt.executeUpdate(sql);
                String response = "";
                try (ResultSet rs = stmt.executeQuery("SELECT * FROM HELLO;")) {
                    while (rs.next()) {
                        int id = rs.getInt("id");
                        String name = rs.getString("name");
                        response += String.format("ID = %d\nNAME = %s", id, name);
                    }
                }
                return response;
            }
        } finally {
            try {
                if (c != null) c.close();
            } catch (SQLException e) {
                // we can ignore error here
            }
        }
    }

}