import java.sql.*;

public class SQLAgent {
    private ConnPool connPool;
    private Connection conn;
    private String driverName;
    private String jdbcURL;
    private String username;
    private String password;

    public void setConnPool(ConnPool pool) {
        connPool = pool;
    }

    public void setDriverName(String drvName) {
        driverName = drvName;
    }

    public void setJdbcURL(String url) {
        jdbcURL = url;
    }

    public void setUserName(String uname) {
        username = uname;
    }

    public void setPassword(String passwd) {
        password = passwd;
    }

    public Connection getConnection() {
        return conn;
    }

    public void setConnectionSwitch(String on_off) throws SQLException {
        if (on_off.equalsIgnoreCase("ON")) {
            if (connPool != null)
                openDB(connPool);
            else
                openDB(driverName, jdbcURL, username, password);
        } else if (on_off.equalsIgnoreCase("OFF"))
            closeDB();
    }

    public void openDB(ConnPool pool) throws SQLException {
        if (conn != null && !conn.isClosed())
            throw new SQLException(
                    "The connection has been established already.");
        if (pool == null)
            throw new SQLException("The connection pool cannot be found.");
        connPool = pool;
        conn = connPool.getConnection();
    }

    public void openDB(String drvName, String url, String uname, String passwd)
            throws SQLException {
        if (conn != null && !conn.isClosed())
            throw new SQLException(
                    "The connection has been established already.");
        try {
            Class.forName(drvName);
        } catch (ClassNotFoundException ex) {
            throw new SQLException(ex.toString());
        }
        conn = DriverManager.getConnection(url, uname, passwd);
    }

    public void closeDB() throws SQLException {
        if (connPool != null) {
            connPool.returnConnection();
            connPool = null;
        } else {
            if (conn == null)
                throw new SQLException("This connection is null.");
            if (conn.isClosed())
                throw new SQLException(
                        "This connection has been close already..");
            conn.close();
        }
        conn = null;
    }

}