Java Threads and MySQL

问题:

I have a threaded chat server application which requires MySQL authencation.

Is the best way to have 1 class create the MySQL connection, keep that connection open and let every thread use that connection but use own Query handler?

Or is it better to have all threads make a seperate connection to MySQL to authencate?

Or is it better to let 1 class handle the queries AND connections?

We are looking at a chatserver that should be able to handle upto 10.000 connections/users.

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I am now using c3p0, and I created this:

public static void main(String[] args) throws PropertyVetoException {     ComboPooledDataSource pool = new ComboPooledDataSource();     pool.setDriverClass("com.mysql.jdbc.Driver");     pool.setJdbcUrl("jdbc:mysql://localhost:3306/db");     pool.setUser("root");     pool.setPassword("pw");     pool.setMaxPoolSize(100);     pool.setMinPoolSize(10);      Database database = new Database(pool);     try     {          ResultSet rs = database.query("SELECT * FROM `users`");          while (rs.next()) {             System.out.println(rs.getString("userid"));             System.out.println(rs.getString("username"));         }     }     catch(Exception ex)     {         System.out.println(ex.getMessage());     }     finally     {         database.close();     } 

}

public class Database {

ComboPooledDataSource pool; Connection conn; ResultSet rs = null; Statement st = null;  public Database (ComboPooledDataSource p_pool) {     pool = p_pool; }  public ResultSet query (String _query) {     try {         conn = pool.getConnection();         st = conn.createStatement();         rs = st.executeQuery(_query);     } catch (SQLException e) {         e.printStackTrace();     } finally {      }     return rs; }  public void close () {     try {         st.close();         conn.close();     } catch (SQLException e) {         e.printStackTrace();     } } 

}

Would this be thread safe?

回答1:

Have you looked at connection pooling ? Check out (for example) Apache DBCP or C3P0.

Briefly, connection pooling means that a pool of authenticated connections are used, and free connections are passed to you on request. You can configure the number of connections as appropriate. When you close a connection, it's actually returned to the pool and made available for another client. It makes life relatively easy in your scenario, since the pool looks after the authentication and connection management.

回答2:

c3p0 connection pool is a robust solution. You can also check dbcp but c3p0 shows better performance, supports auto-reconnection and some other features.

回答3:

You should not have just one connection. It's not a thread-safe class. The idea is to get a connection, use it, and close it in the narrowest scope possible.

Yes, you'll need a pool of them. Every Java EE app server will have a JNDI pooling mechanism for you. I wouldn't recommend one class for all queries, either. Your chat ap

Your chat app ought to have a few sensible objects in its domain model. I'd create data access objects for them as appropriate. Keep the queries related to a particular domain model object in its DAO.

回答4:

is the info in this thread up-to-date? Googling brings up a lot of different things, as well as this - http://dev.mysql.com/tech-resources/articles/connection_pooling_with_connectorj.html

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