Backend API. Server-side code: this runs in a Codename One backend, not in the app on the device.

public final class DbPool

  1. Object
  2. DbPool

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.

Methods

public static DbPool open(String path, int size, int busyTimeoutMillis) throws IOExceptionOpens size connections to path and puts the database in WAL mode.
public synchronized Db borrow() throws IOExceptionTakes a connection, blocking until one is free.
public synchronized void release(Db db)
public Object withConnection(Db.Work body) throws ExceptionBorrows a connection, runs body, and returns it however body ends.
public Object inTransaction(Db.Work body) throws ExceptionConvenience: one transaction on a pooled connection.
public synchronized void close()

Inherited methods

From Object

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

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

Throws

IOException

release

public synchronized 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 synchronized void close()