I'm writing a servlet that handles each request by accessing and modifying some table(s) in the database. I want the connections to the database to be thread safe. I don't want to use already existing libraries/frameworks for this (spring, hibernate, etc.).
I know I can use java's ThreadLocal for this in the following way :
public class DatabaseRegistry { //assume it's a singleton
private Properties prop = new Properties();
public static final ThreadLocal<Connection> threadConnection = new ThreadLocal<Connection>();
private Connection connect() throws SQLException {
try {
// This will load the MySQL driver, each DB has its own driver
Class.forName("com.mysql.jdbc.Driver");
// Setup the connection with the DB
Connection connection = DriverManager
.getConnection("jdbc:mysql://" + prop.getProperty("hostname") + "/" + prop.getProperty("database") + "?"
+ "user=" + prop.getProperty("username") + "&password=" + prop.getProperty("password"));
return connection;
} catch (SQLException e) {
throw e;
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return null;
}
public Connection getConnection() throws SQLException {
if (threadConnection.get() == null) {
Connection connection = connect();
threadConnection.set(connection);
return threadConnection.get();
} else {
return threadConnection.get();
}
}
private void freeConnection(Connection connection) throws SQLException {
connection.close();
threadConnection.remove();
}
}
Each time you call getConnection(), the new connection is added to the ThreadLocal object and then removed when you free the connection.
Is this the proper way of doing this or should the DatabaseRegistry itself extend the ThreadLocal<Connection> class? Or is there an even better way to do this to make all connections thread safe?
