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package uk.org.ury.database;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import uk.org.ury.database.exceptions.ConnectionFailureException;
import uk.org.ury.database.exceptions.MissingCredentialsException;
/**
* A database connection manager that connects to the URY databases
* using suitably privileged accounts, and handles the processing
* of SQL queries.
*
* @author Matt Windsor
*
*/
public class DatabaseDriver
{
/* The JDBC path used to connect to the URY database. */
private String DATABASE_PATH = "jdbc:postgresql://4574.co.uk/membership";
/* The database connection. */
private Connection conn;
/**
* Construct a new DatabaseDriver with the given user class.
*
* @param userclass The user class to log in to the database with.
*
* @throws IllegalArgumentException if the user class is
* not supported (this should not happen).
*
* @throws MissingCredentialsException if the user class
* login credentials could not be loaded.
*
* @throws ConnectionFailureException if the database
* backend failed to connect to the database
* server.
*/
public
DatabaseDriver (UserClass userclass)
throws MissingCredentialsException, ConnectionFailureException
{
DatabaseLogin login = null;
login = DatabaseLogin.getLoginFromFile (userclass.configName + ".txt");
try
{
connect (login);
}
catch (SQLException e)
{
throw new ConnectionFailureException (e.getMessage ());
}
}
/**
* Connect to the URY database.
*
* @param login The login tuple to use for the connection.
*
* @throws SQLException if the database connection failed.
*/
private void
connect (DatabaseLogin login) throws SQLException
{
if (login == null)
throw new IllegalArgumentException ("Supplied null login.");
if (login.getUsername () == null)
throw new IllegalArgumentException ("Login has no associated username.");
if (login.getPassword () == null)
throw new IllegalArgumentException ("Login has no associated password.");
conn = DriverManager.getConnection (DATABASE_PATH,
login.getUsername (),
login.getPassword ());
}
/**
* Execute an unprepared SQL statement with no arguments.
*
* @param sql The SQL statement to execute.
* @param fetchSize The maximum number of query rows to return.
*
* @return the JDBC results set.
*/
public ResultSet
executeQuery (String sql, int fetchSize)
{
try
{
Statement st = conn.createStatement ();
st.setFetchSize (fetchSize);
return st.executeQuery (sql);
}
catch (SQLException e)
{
e.printStackTrace ();
return null;
}
}
/**
* Perform a SQL statement with arguments.
*
* This accepts an array of parameter objects, which must each
* either be String or Integer objects. The objects will be used
* sequentially to fill in '?' placeholders in the query text.
*
* @param sql The SQL statement to execute.
* @param params A list of parameter objects.
* @param fetchSize The maximum number of query rows to return.
*
* @return the set of results from the query.
*
* @throws IllegalArgumentException if any of the
* parameters is unsupported by the database as
* a statement parameter.
*
* @throws SQLException if a SQL error occurs.
*/
public ResultSet
executeQuery (String sql, Object[] params, int fetchSize) throws SQLException
{
PreparedStatement st = conn.prepareStatement (sql);
st.setFetchSize (50);
for (int i = 0; i < params.length; i++)
if (params[i] instanceof String)
st.setString (i + 1, (String) params[i]);
else if (params[i] instanceof Integer)
st.setInt (i + 1, (Integer) params[i]);
else
throw new IllegalArgumentException ("Unsupported parameter #" + (i + 1));
return st.executeQuery ();
}
}
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