sos.db
Class InMemoryDatabase

java.lang.Object
  sos.db.AbstractDatabase
      sos.db.AbstractSerializationDatabase
          sos.db.InMemoryDatabase

All Implemented Interfaces:

java.io.Serializable, Database

public class InMemoryDatabase
extends AbstractSerializationDatabase
implements Database

A non-persistent database that stores objects in memory. Since the database is entirely in memory, database objects cannot persist across multiple executions. Each time the application starts, it will have an empty database, which must be initialized with create. Most applications will use FileDatabase rather than this class.

This class is useful for applications wishing to use a temporary database, such as a cache. Also, applets can use this database without requiring access to the host's file system.

Logging

Instances of this database log database activity. See AbstractSerializationDatabase for more information.

External Serialization

Proxy objects can be serialized to a stream outside of the database. See AbstractSerializationDatabase for more information.

Since:

1.0

See Also:

Database, AbstractSerializationDatabase, TransactionPolicy, FileDatabase

Field Summary

Fields inherited from interface sos.db.Database

logger

Constructor Summary

InMemoryDatabase(java.lang.String databaseName)
Creates an instance of InMemoryDatabase with the specified database name.

InMemoryDatabase(java.lang.String databaseName, TransactionPolicy policy)
Creates a InMemoryDatabase with the specified database name and transaction policy.

Method Summary

protected boolean	doDelete() Performs the action of delete.
protected boolean	doExists() Performs the action of exists.
protected byte[]	doFetchObject(long id) Returns the serialized object associated with id.
protected boolean	doFlush(LongMap<byte[]> newObjects, LongMap<byte[]> modifiedObjects, Progress progress) Adds new objects, re-saves modified objects, and removes old objects from this database in a single, atomic step.
protected long	doNextKey(long fromKey) Returns the next key greater than or equal to fromKey that corresponds to an object in this database.
protected void	doRemoveObject(long oldKey) Removes the specified object from this database.

Methods inherited from class sos.db.AbstractSerializationDatabase

createDefaultTransactionPolicy, doAbortTransaction, doAddObject, doClose, doCommitTransaction, doContainsObject, doCreate, doGetRoot, doOpen, doStartTransaction, doTransactionDepth, enableReplaceObject, getName, getTransactionPolicy, logDatabaseClosed, logDatabaseCreated, logDatabaseDeleted, logDatabaseOpened, logObjectAdded, logObjectRemoved, logObjectResaved, logTransactionAborted, logTransactionCommitted, logTransactionStarted, readResolve, replaceObject, resolveObject, setAutoCreateTransactions

Methods inherited from class sos.db.AbstractDatabase

abortTransaction, addObject, close, commitTransaction, containsObject, create, delete, exists, getRoot, isOpen, open, startTransaction, transactionDepth

Methods inherited from class java.lang.Object

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

Methods inherited from interface sos.db.Database

abortTransaction, addObject, close, commitTransaction, containsObject, create, delete, exists, getName, getRoot, getTransactionPolicy, isOpen, open, startTransaction, transactionDepth

Constructor Detail

InMemoryDatabase

public InMemoryDatabase(java.lang.String databaseName)

Creates an instance of InMemoryDatabase with the specified database name. The name is used only in the logging of messages.

Parameters:

databaseName - name of this database

See Also:

InMemoryDatabase(String,TransactionPolicy)

InMemoryDatabase

public InMemoryDatabase(java.lang.String databaseName,
                        TransactionPolicy policy)

Creates a InMemoryDatabase with the specified database name and transaction policy.

Parameters:

databaseName - name of the database

policy - policy to use to control transactions (may be null)

Method Detail

doDelete

protected boolean doDelete()
                    throws java.io.IOException

Description copied from class: AbstractDatabase

Performs the action of delete. This method is called inside delete if this database is in an acceptable state. It has the same semantics as delete.

Overrides:

doDelete in class AbstractSerializationDatabase

Returns:

true if this database is successfully deleted

Throws:

java.io.IOException - if an I/O error occurs

See Also:

AbstractDatabase.delete()

doExists

protected boolean doExists()

Description copied from class: AbstractDatabase

Performs the action of exists. This method is called inside exists if this database is in an acceptable state. It has the same semantics as exists.

Specified by:

doExists in class AbstractDatabase

Returns:

true if this database exists

See Also:

AbstractDatabase.exists()

doFetchObject

protected byte[] doFetchObject(long id)
                        throws java.io.IOException

Description copied from class: AbstractSerializationDatabase

Returns the serialized object associated with id.

This method is called while holding this database's monitor.

Specified by:

doFetchObject in class AbstractSerializationDatabase

Parameters:

id - id of object to fetch

Returns:

the serialized object associated with id

Throws:

java.io.IOException - if an I/O error occurs

doFlush

protected boolean doFlush(LongMap<byte[]> newObjects,
                          LongMap<byte[]> modifiedObjects,
                          Progress progress)
                   throws java.io.IOException

Description copied from class: AbstractSerializationDatabase

Adds new objects, re-saves modified objects, and removes old objects from this database in a single, atomic step. If any of these steps should fail, the database should roll back to its state prior to the call.

This method is called when a top-level transaction commits. It is called while holding this database's monitor.

Specified by:

doFlush in class AbstractSerializationDatabase

Parameters:

newObjects - a mapping of new ids (as Longs) to new database objects (as byte[]s)

modifiedObjects - a mapping of ids (as Longs) to modified database objects (as byte[]s)

progress - an object to be updated and checked as the flush is occurring (may be null)

Returns:

false if it is interrupted because the progress is canceled; true otherwise

Throws:

java.io.IOException - if an I/O error occurs

doRemoveObject

protected void doRemoveObject(long oldKey)
                       throws java.io.IOException

Description copied from class: AbstractSerializationDatabase

Removes the specified object from this database.

This method is called when a garbage collection finds the object unreachable. It is called while holding this database's monitor.

Specified by:

doRemoveObject in class AbstractSerializationDatabase

Parameters:

oldKey - keys of the object to remove from this database

Throws:

java.io.IOException - if an I/O error occurs

doNextKey

protected long doNextKey(long fromKey)
                  throws java.io.IOException

Description copied from class: AbstractSerializationDatabase

Returns the next key greater than or equal to fromKey that corresponds to an object in this database. This method is called while holding this database's monitor.

Specified by:

doNextKey in class AbstractSerializationDatabase

Parameters:

fromKey - key from which to start the search

Returns:

the key of the next database object or -1, if no more database objects

Throws:

java.io.IOException - if an I/O error occurs