Class DbPool

java.lang.Object

com.codename1.backend.DbPool

public final class DbPool
extends Object

A fixed pool of connections to one SQLite database.

Why a pool at all, when SQLite is compiled SQLITE_THREADSAFE=1 and a single connection is already safe to share: serialized mode makes concurrent use SAFE by serializing it, which means one connection gives no read concurrency at all. Several connections against a WAL database do, because WAL lets readers proceed while a writer is active.

The pool is deliberately fixed-size and blocking rather than growing on demand: an unbounded pool against a single file just moves the contention into SQLite and makes the busy-timeout the thing that fails.

Method Summary

Modifier and Type	Method	Description
Db	borrow()	Takes a connection, blocking until one is free.
void	close()
Object	inTransaction(Db.Work body)	Convenience: one transaction on a pooled connection.
static DbPool	open(String path, int size, int busyTimeoutMillis)	Opens size connections to path and puts the database in WAL mode.
void	release(Db db)
Object	withConnection(Db.Work body)	Borrows a connection, runs body, and returns it however body ends.

Methods inherited from class Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

open

public static DbPool open(String path,
 int size,
 int busyTimeoutMillis)
                   throws IOException

Opens size connections to path and puts the database in WAL mode.

A ":memory:" database cannot be pooled - each connection would get its OWN private database - so that is rejected rather than silently giving every caller a different empty database.

Throws:

IOException

borrow

public Db borrow()
          throws IOException

Takes a connection, blocking until one is free. Always release it in a finally, or prefer withConnection(Db.Work), which cannot leak one.

Throws:

IOException

release

public void release(Db db)

withConnection

public Object withConnection(Db.Work body)
                      throws Exception

Borrows a connection, runs body, and returns it however body ends.

Throws:

Exception

inTransaction

public Object inTransaction(Db.Work body)
                     throws Exception

Convenience: one transaction on a pooled connection.

Throws:

Exception

close

public void close()