org.mmbase.storage
Interface Storage

All Known Subinterfaces:

DatabaseStorage

public interface Storage

The Storage interface defines a storage device - a location where MMBase objects are kept, typically a database. The interface contains methods that can be used to query the storage, insert, update, or remove objects, or to change object definitions (adding fields, etc.).

Since:

MMBase-1.6

Version:

$Id: Storage.java,v 1.2 2002/11/07 12:30:37 pierre Exp $

Author:

Pierre van Rooden

Method Summary

boolean	addField(MMObjectBuilder builder, java.lang.String fieldname) Adds a field to the storage of this builder.
boolean	changeField(MMObjectBuilder builder, java.lang.String fieldname) Changes a field to the storage of this builder.
boolean	commit(MMObjectNode node) Commit this node to the specified builder.
boolean	commit(MMObjectNode node, Transaction trans) Commit this node to the specified builder within a transaction.
boolean	create(MMObjectBuilder builder) Create a storage for the specified builder.
boolean	create(MMObjectBuilder builder, Transaction trans) Create a storage for the specified builder.
boolean	created(MMObjectBuilder builder) Tells if a storage for the builder already exists
int	createKey() Gives an unique number for a node to be inserted.
int	createKey(Transaction trans) Gives an unique number for a node to be inserted.
boolean	createObjectStorage() Create the object storage (the storage where to register all objects).
boolean	createObjectStorage(Transaction trans) Create the object storage (the storage where to register all objects) within a transaction
Transaction	createTransaction() Returns a newly created transaction object.
boolean	delete(MMObjectNode node) Delete a node
boolean	delete(MMObjectNode node, Transaction trans) Delete a node within a transaction
boolean	drop(MMObjectBuilder builder) Drops the storage of this builder.
byte[]	getBytes(MMObjectNode node, java.lang.String fieldname) Retrieve a large binary object (byte array) for a specified object field.
MMObjectNode	getNode(MMObjectBuilder builder, int number) Select a node from a specified builder
MMObjectNode	getNode(MMObjectBuilder builder, int number, Transaction trans) Select a node from a specified builder
int	getNodeType(int number) Returns the nodetype for a specified nodereference
int	getNodeType(int number, Transaction trans) Returns the nodetype for a specified nodereference
java.lang.String	getText(MMObjectNode node, java.lang.String fieldname) Retrieve a large text for a specified object field.
int	insert(MMObjectNode node) This method inserts a new object, and registers the change.
int	insert(MMObjectNode node, Transaction trans) This method inserts a new object within a transaction, and registers the change.
boolean	isAllowedParentBuilder(MMObjectBuilder builder) Returns whether this storage layer allows for builder to be a parent builder (that is, other builders can 'extend' this builder and its storage device).
void	registerParentBuilder(MMObjectBuilder parent, MMObjectBuilder child) Registers a builder as a parent builder (that is, other builders can 'extend' this builder and its storage device).
boolean	removeField(MMObjectBuilder builder, java.lang.String fieldname) Deletes a field from the storage of this builder.
int	size(MMObjectBuilder builder) Return number of objects in a builder
boolean	supportsRollback() Returns whether rollback on storage level is supported.
boolean	updateStorage(MMObjectBuilder builder) Changes the storage of a builder to match its new configuration.

Method Detail

isAllowedParentBuilder

public boolean isAllowedParentBuilder(MMObjectBuilder builder)

Returns whether this storage layer allows for builder to be a parent builder (that is, other builders can 'extend' this builder and its storage device).

Parameters:

builder - the builder to test

Returns:

true if the builder can be extended

Since:

MMBase-1.6

registerParentBuilder

public void registerParentBuilder(MMObjectBuilder parent,
                                  MMObjectBuilder child)
                           throws StorageException

Registers a builder as a parent builder (that is, other builders can 'extend' this builder and its storage device). At the least, this code should check whether the builder is allowed as a parent builder, and throw an exception if this is not possible.

Parameters:

parent - the parent builder to register

child - the builder to register as the parent's child

Throws:

StorageException - when the support layer does not allow extension of this builder

Since:

MMBase-1.6

supportsRollback

public boolean supportsRollback()

Returns whether rollback on storage level is supported.

Returns:

true if transactions are supported

getText

public java.lang.String getText(MMObjectNode node,
                                java.lang.String fieldname)

Retrieve a large text for a specified object field. Implement this method to allow for optimization of storing and retrieving large texts.

Parameters:

node - the node to retrieve the text from

fieldname - the name of the field to retrieve

Returns:

the retrieved text

getBytes

public byte[] getBytes(MMObjectNode node,
                       java.lang.String fieldname)

Retrieve a large binary object (byte array) for a specified object field. Implement this method to allow for optimization of storing and retrieving binary objects.

Parameters:

node - the node to retrieve the byte array from

fieldname - the name of the field to retrieve

Returns:

the retrieved byte array

createTransaction

public Transaction createTransaction()
                              throws StorageException

Returns a newly created transaction object.

Returns:

the new transaction

Throws:

StorageException - if the transaction could not be created

createKey

public int createKey()

Gives an unique number for a node to be inserted. This method should work with multiple mmbases

Returns:

unique number

createKey

public int createKey(Transaction trans)
              throws StorageException

Gives an unique number for a node to be inserted. This method should work with multiple mmbases

Parameters:

trans - the transaction to use for obtaining the key

Returns:

unique number

Throws:

StorageException - if an error occurred during key generation

insert

public int insert(MMObjectNode node)

This method inserts a new object, and registers the change. Only fields with states of DBSTATE_PERSISTENT or DBSTATE_SYSTEM are stored.

Parameters:

node - The node to insert

Returns:

The (new) number for this node, or -1 if an error occurs.

insert

public int insert(MMObjectNode node,
                  Transaction trans)
           throws StorageException

This method inserts a new object within a transaction, and registers the change. Only fields with states of DBSTATE_PERSISTENT or DBSTATE_SYSTEM are stored.

Parameters:

node - The node to insert

trans - the transaction to perform the insert in

Returns:

The (new) number for this node, or -1 if an error occurs.

Throws:

StorageException - if an error occurred during insert

commit

public boolean commit(MMObjectNode node)

Commit this node to the specified builder.

Parameters:

node - The node to commit

Returns:

true of succesful, false otherwise

commit

public boolean commit(MMObjectNode node,
                      Transaction trans)
               throws StorageException

Commit this node to the specified builder within a transaction.

Parameters:

node - The node to commit

trans - the transaction to perform the insert in

Returns:

true of succesful, false otherwise

Throws:

StorageException - if an error occurred during commit

delete

public boolean delete(MMObjectNode node)

Delete a node

Parameters:

node - The node to delete

Returns:

true if succesful

delete

public boolean delete(MMObjectNode node,
                      Transaction trans)
               throws StorageException

Delete a node within a transaction

Parameters:

node - The node to delete

trans - the transaction to perform the insert in

Returns:

true if succesful

Throws:

StorageException - if an error occurred during delete

getNode

public MMObjectNode getNode(MMObjectBuilder builder,
                            int number)

Select a node from a specified builder

Parameters:

builder - The builder to select from

number - the number of the node

Returns:

the MMObjectNode that was found, or null f it doesn't exist

getNode

public MMObjectNode getNode(MMObjectBuilder builder,
                            int number,
                            Transaction trans)
                     throws StorageException

Select a node from a specified builder

Parameters:

builder - The builder to select from

number - the number of the node

trans - the transaction to perform the insert in

Returns:

the MMObjectNode that was found, or null f it doesn't exist

Throws:

StorageException - if an error occurred during the get

getNodeType

public int getNodeType(int number)

Returns the nodetype for a specified nodereference

Parameters:

number - the number of the node

Returns:

int the object type or -1 if not found

getNodeType

public int getNodeType(int number,
                       Transaction trans)
                throws StorageException

Returns the nodetype for a specified nodereference

Parameters:

number - the number of the node

trans - the transaction to perform the insert in

Returns:

int the object type or -1 if not found

Throws:

StorageException - if an error occurred during selection

create

public boolean create(MMObjectBuilder builder)

Create a storage for the specified builder.

Parameters:

builder - the builder to create the storage for

Returns:

true if the storage was succesfully created

create

public boolean create(MMObjectBuilder builder,
                      Transaction trans)
               throws StorageException

Create a storage for the specified builder.

Parameters:

builder - the builder to create the storage for

trans - the transaction to perform the create in

Returns:

true if the storage was succesfully created

Throws:

StorageException - if an error occurred during the creation fo the table

createObjectStorage

public boolean createObjectStorage()

Create the object storage (the storage where to register all objects).

Returns:

true if the storage was succesfully created

createObjectStorage

public boolean createObjectStorage(Transaction trans)
                            throws StorageException

Create the object storage (the storage where to register all objects) within a transaction

Parameters:

trans - the transaction to perform the create in

Returns:

true if the storage was succesfully created

Throws:

StorageException - if an error occurred during the caretion of the object storage

created

public boolean created(MMObjectBuilder builder)

Tells if a storage for the builder already exists

Parameters:

builder - the builder to check

Returns:

true if storage exists, false if storage doesn't exists

size

public int size(MMObjectBuilder builder)

Return number of objects in a builder

Parameters:

builder - the builder whose objects to count

Returns:

the number of objects the builder has, or -1 if the builder does not exist.

drop

public boolean drop(MMObjectBuilder builder)

Drops the storage of this builder.

Parameters:

builder - the builder whose storage to drop

Returns:

true if succesful

addField

public boolean addField(MMObjectBuilder builder,
                        java.lang.String fieldname)

Adds a field to the storage of this builder.

Parameters:

builder - the builder whose storage to change

fieldname - the name fo the field to add

Returns:

true if succesful

removeField

public boolean removeField(MMObjectBuilder builder,
                           java.lang.String fieldname)

Deletes a field from the storage of this builder.

Parameters:

builder - the builder whose storage to change

fieldname - the name fo the field to delete

Returns:

true if succesful

changeField

public boolean changeField(MMObjectBuilder builder,
                           java.lang.String fieldname)

Changes a field to the storage of this builder.

Parameters:

builder - the builder whose storage to change

fieldname - the name fo the field to change

Returns:

true if succesful

updateStorage

public boolean updateStorage(MMObjectBuilder builder)

Changes the storage of a builder to match its new configuration.

Parameters:

builder - the builder whose storage to change

Returns:

true if succesful