JDBC的各种连接

Question

I'm creating app for library management with Java and MySQL ( JDBC to connect with DB ) , and I have a problem , I checked a lot of topics, books, and websites but I didn't find good answer for me. Is it the good way to deal with connections ? I think that one connection for entire app is good option in this case. My idea is that in every function in every class when I need to use Connection object , these functions will need a connection parameter. In main class I'll call manager object 'Man' for example and to every constructor etc I'll pass Man.getMyConn() as this parameter and call Man.close() when Main frame will be closed . Is it bad idea ? Maybe I should use singleton pattern or connection pool ? Sorry for my English , I'm still learning.

public class manager {
private Connection myConn;

public manager() throws Exception {


    Properties props = new Properties();
    props.load(new FileInputStream("app.properties"));

    String user = props.getProperty("user");
    String password = props.getProperty("password");
    String dburl = props.getProperty("dburl");


    myConn = DriverManager.getConnection(dburl, user, password);
    System.out.println("DB connection successful to: " + dburl);
}

public Connection getMyConn() {
    return myConn;
}
  //close class etc.
}

Answer 1

Usually not. Further answer depends on type of the application. If you're making web application then you should definitely go with connection pool. If you're making eg desktop application (where only one user can access it at the time), then you can open and close connection upon each request.

Answer 2

I have working applications that do it your way. As @Branislav says, it's not adequate if you want to do multiple concurrent queries. There's also a danger that the connection to the database might be lost, and you would need to restart your application to get a new one, unless you write code to catch that and recreate the connection.

Using a singleton would be overcomplicated. Having a getConnection() method (as you have done) is very important as it means you can easily change your code to use a pool later if you find you need to.