Should a database connection stay open all the time or only be opened when needed?

Question

I have a bukkit plugin (minecraft) that requires a connection to the database.

Should a database connection stay open all the time, or be opened and closed when needed?

Answer 1

The database connection must be opened only when its needed and closed after doing all the necessary job with it. Code sample:

• Prior to Java 7:

    Connection con = null;   try {       con = ... //retrieve the database connection       //do your work...   } catch (SQLException e) {       //handle the exception   } finally {       try {           if (con != null) {               con.close();           }       } catch (SQLException shouldNotHandleMe) {           //...       }   } 

• Java 7:

    try (Connection con = ...) {   } catch (SQLException e) {   }   //no need to call Connection#close since now Connection interface extends Autocloseable 

But since manually opening a database connection is too expensive, it is highly recommended to use a database connection pool, represented in Java with DataSource interface. This will handle the physical database connections for you and when you close it (i.e. calling Connection#close), the physical database connection will just be in SLEEP mode and still be open.

Related Q/A:

• Java Connection Pooling

Some tools to handle database connection pooling:

• BoneCP
• c3po
• Apache Commons DBCP
• HikariCP

Answer 2

Depends on what are your needs.

Creating a connection takes some time, so if you need to access database frequently it's better to keep the connection open. Also it's better to create a pool, so that many users can access database simultaneously(if it's needed).

If you need to use this connection only few times you may not keep it open, but you will have delay when you would like to access database. So i suggest you to make a timer that will keep connection open for some time(connection timeout).