org.mmbase.storage.database
Class SQL92DatabaseStorage

java.lang.Object
  |
  +--org.mmbase.storage.database.Support2Storage
        |
        +--org.mmbase.storage.database.AbstractDatabaseStorage
              |
              +--org.mmbase.storage.database.SQL92DatabaseStorage

All Implemented Interfaces:

DatabaseStorage, MMJdbc2NodeInterface, Storage

Direct Known Subclasses:

OODatabaseStorage, RelationalDatabaseStorage

public abstract class SQL92DatabaseStorage

extends AbstractDatabaseStorage

implements DatabaseStorage

SQL92DatabaseStorage extends AbstractDatabaseStorage to implement the basic functionality for creating and updating databse tables, using SQL. Most statements created here are ANSI SQL 92, with the exception of statements for creating extended tables (see create(org.mmbase.module.core.MMObjectBuilder, org.mmbase.storage.Transaction)). It does not take into account db-specific effects of inheritance - as various databases have their own methods, it may be necessary to override the create(org.mmbase.module.core.MMObjectBuilder, org.mmbase.storage.Transaction), insertIntoTable(org.mmbase.module.core.MMObjectBuilder, org.mmbase.module.core.MMObjectNode, org.mmbase.storage.database.DatabaseTransaction), commitToTable(org.mmbase.module.core.MMObjectBuilder, org.mmbase.module.core.MMObjectNode, org.mmbase.storage.database.DatabaseTransaction), and deleteFromTable(org.mmbase.module.core.MMObjectBuilder, org.mmbase.module.core.MMObjectNode, org.mmbase.storage.database.DatabaseTransaction) methods. The basic implementation of these methods assumes an OO-database that does not require the use of specific database routines (i.e. alternate SQL syntax). Furthermore, most sql statements are now contained in their own wrapper methods: createSQL(java.lang.String, java.lang.String, java.lang.String, java.lang.String), insertSQL(java.lang.String, java.lang.String, java.lang.String), updateSQL(java.lang.String, java.lang.String, int), deleteSQL(java.lang.String, int) and various methods for returning SQL SELECT statements. You can override these method to change the sql statements used by the database layer.

Since:

MMBase-1.6

Version:

$Id: SQL92DatabaseStorage.java,v 1.4.2.1 2003/02/21 11:58:51 michiel Exp $

Author:

Pierre van Rooden

Fields inherited from class org.mmbase.storage.database.AbstractDatabaseStorage

mmb

Fields inherited from interface org.mmbase.storage.database.DatabaseStorage

KEY_FOREIGN, KEY_NONE, KEY_NOTNULL, KEY_PRIMARY, KEY_SECONDARY

Constructor Summary

protected

SQL92DatabaseStorage() Constructs the AbstractDatabaseSupport database layer support class

Method Summary

boolean	addField(MMObjectBuilder builder, java.lang.String fieldname) Adds a field to the table of this builder.
protected java.lang.String	applyCreateScheme(java.lang.String tableName, java.lang.String fieldDefinitions, java.lang.String parentTableName) Applies the create scheme (if available), and returns the result (a field type defintiton string)
boolean	changeField(MMObjectBuilder builder, java.lang.String fieldname) Changes a field to the table of this builder.
boolean	commit(MMObjectNode node, Transaction trans) Commit this node to the specified builder table within a transaction.
protected boolean	commitToTable(MMObjectBuilder builder, MMObjectNode node, DatabaseTransaction trans) Commit the changes to this node to the specified builder table.
boolean	create(MMObjectBuilder builder, Transaction trans) Create a database table for the specified builder.
boolean	created(MMObjectBuilder builder) Tells if a table for the builder already exists
boolean	created(java.lang.String tableName) Tells if a table already exists
boolean	createObjectStorage(Transaction trans) Create the object table (the basic table for all objects) within a transaction
protected java.lang.String	createSQL(java.lang.String tableName, java.lang.String fields, java.lang.String parentTableName, java.lang.String parentFields) Returns the SQL command to use for creating a specified table, optionally extending another supplied table.
boolean	delete(MMObjectNode node, Transaction trans) Delete a node within a transaction
boolean	deleteFromTable(MMObjectBuilder builder, MMObjectNode node, DatabaseTransaction trans) Remove a node from the specified builder table.
protected java.lang.String	deleteSQL(java.lang.String tableName, int number) Returns the SQL command to use for deleting an object in a table.
boolean	drop(MMObjectBuilder builder) Drops the table of this builder.
protected java.lang.String	dropSQL(java.lang.String tableName) Returns the SQL command to use for dropping a specified table Overide this method to add a database-specific syntax or optimalization
byte[]	getBytes(MMObjectNode node, java.lang.String fieldname) Get bytes from blob
protected abstract byte[]	getBytes(java.lang.String tableName, java.lang.String fieldname, int number) Get bytes from blob
protected java.util.List	getFieldsOrderCreate(MMObjectBuilder builder) Returns the fields of a builder in the order in which they should be created.
MMObjectNode	getNode(MMObjectBuilder builder, int number, Transaction trans) Select a node from a specified builder
int	getNodeType(int number, Transaction trans) Returns the nodetype for a specified nodereference
protected MMObjectBuilder	getParentBuilder(MMObjectBuilder builder) Returns the parent builder of the specifed builder.
protected java.lang.String	getParentTableName(MMObjectBuilder builder) Returns the name of the parent table of the specifed builder.
java.lang.String	getText(MMObjectNode node, java.lang.String fieldname) Get text from blob
protected abstract java.lang.String	getText(java.lang.String tableName, java.lang.String fieldname, int number) Get text from blob
void	init(MMBase mmb, XMLDatabaseReader document) Initializes the database layer.
int	insert(MMObjectNode node, Transaction trans) This method inserts a new object within a transaction, and registers the change.
protected int	insertIntoTable(MMObjectBuilder builder, MMObjectNode node, DatabaseTransaction trans) This method inserts a new object in a specified builder table.
protected java.lang.String	insertSQL(java.lang.String tableName, java.lang.String fieldNames, java.lang.String fieldValues) Returns the SQL command to use for inserting an object in a table.
boolean	isAllowedParentBuilder(MMObjectBuilder builder) Returns whether this database support layer allows for builder to be a parent builder (that is, other builders can 'extend' this builder and its database tables).
protected boolean	isParentField(MMObjectBuilder builder, java.lang.String fieldName) Tests whether the specified field is a member of the parent table of the specifed builder.
protected void	loadExistingTables() Load the names of the existing tables for this MMBase instance in memory.
void	loadFieldFromTable(MMObjectNode node, java.lang.String fieldname, java.sql.ResultSet rs, int i) Stores a field in a table ResultSet in a MMObjectNode.
protected void	loadSupportInformation() Load information on database support (i.e support of rollback).
protected void	prepare() Prepares the database layer.
protected byte[]	readBytesFromFile(java.lang.String filename) Reads a byte array from a file.
boolean	removeField(MMObjectBuilder builder, java.lang.String fieldname) Deletes a field from the table of this builder.
protected java.lang.String	selectSQL(java.lang.String tableName, java.lang.String fieldNames, java.lang.String where, java.lang.String orderby, int offset, int max) Returns the SQL command to use for selecting data from a table.
boolean	setValuePreparedStatement(java.sql.PreparedStatement stmt, MMObjectNode node, java.lang.String fieldname, int i) Set a prepared statement field i with value of key from the given node.
int	size(MMObjectBuilder builder) Return number of objects in a builder
int	size(java.lang.String tableName) Return number of entries consisting in given table.
boolean	supportsExtendedTables() Returns whether this storage layer supports extended tables.
boolean	supportsRollback() Returns whether rollback on storage level is supported.
protected java.lang.String	updateSQL(java.lang.String tableName, java.lang.String setFields, int number) Returns the SQL command to use for updating an object in a table.
boolean	updateStorage(MMObjectBuilder builder) Changes the storage of a builder to match its new configuration.
protected boolean	writeBytesToFile(java.lang.String filename, byte[] value) Writes a byte array to a file.

Methods inherited from class org.mmbase.storage.database.AbstractDatabaseStorage

applyForeignKeyScheme, applyKeyScheme, applyNotNullScheme, applyPrimaryKeyScheme, applyScheme, commit, constructFieldDefinition, constructFieldDefinition, create, createDatabaseTransaction, createDatabaseTransaction, createKey, createKey, createObjectStorage, createSQL, createTransaction, delete, deployDatabaseDocument, getBinaryFilePath, getCreateExtendedScheme, getCreateScheme, getFieldNameMap, getForeignKeyScheme, getFullTableName, getJDBC, getKeyScheme, getMaxDropSize, getNode, getNodeType, getNotNullScheme, getNumberString, getPrimaryKeyScheme, getStoreBinaryAsFile, getTypeMap, insert, mapToMMBaseFieldName, mapToTableFieldName, matchType, registerChanged, registerParentBuilder, selectSQL, selectSQL, selectSQL, setBinaryFilePath, setCreateExtendedScheme, setCreateScheme, setDBByte, setDBText, setFieldNameMap, setForeignKeyScheme, setKeyScheme, setMaxDropSize, setNotNullScheme, setPrimaryKeyScheme, setStoreBinaryAsFile, setTypeMap

Methods inherited from class org.mmbase.storage.database.Support2Storage

commit, createObjectTable, decodeDBnodeField, decodeDBnodeField, getAllowedField, getConnection, getDBByte, getDBKey, getDBText, getDisallowedField, getMMNodeSearch2SQL, getOTypeString, getOwnerString, getShortedByte, getShortedText, insert, removeNode, updateTable

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.mmbase.storage.database.DatabaseStorage

deployDatabaseDocument, getBinaryFilePath, getCreateExtendedScheme, getCreateScheme, getFieldNameMap, getForeignKeyScheme, getJDBC, getKeyScheme, getMaxDropSize, getNotNullScheme, getPrimaryKeyScheme, getStoreBinaryAsFile, getTypeMap, mapToMMBaseFieldName, mapToTableFieldName, registerChanged, setBinaryFilePath, setCreateExtendedScheme, setCreateScheme, setFieldNameMap, setForeignKeyScheme, setKeyScheme, setMaxDropSize, setNotNullScheme, setPrimaryKeyScheme, setStoreBinaryAsFile, setTypeMap

Methods inherited from interface org.mmbase.storage.Storage

commit, create, createKey, createKey, createObjectStorage, createTransaction, delete, getNode, getNodeType, insert, registerParentBuilder

Constructor Detail

SQL92DatabaseStorage

protected SQL92DatabaseStorage()

Constructs the AbstractDatabaseSupport database layer support class

Method Detail

init

public void init(MMBase mmb,
                 XMLDatabaseReader document)

Initializes the database layer. This reads database specific content from the database configuration document.

Specified by:

init in interface DatabaseStorage

Overrides:

init in class AbstractDatabaseStorage

Parameters:

mmb - the MBase instance that uses this database layer

document - the database configuration document

loadExistingTables

protected void loadExistingTables()

Load the names of the existing tables for this MMBase instance in memory.

loadSupportInformation

protected void loadSupportInformation()

Load information on database support (i.e support of rollback).

prepare

protected void prepare()

Prepares the database layer. Override this method if you need to make preparations for your database.

supportsExtendedTables

public boolean supportsExtendedTables()

Returns whether this storage layer supports extended tables.

Specified by:

supportsExtendedTables in interface DatabaseStorage

Overrides:

supportsExtendedTables in class AbstractDatabaseStorage

Returns:

boolean true if extended tables are supported

supportsRollback

public boolean supportsRollback()

Returns whether rollback on storage level is supported.

Specified by:

supportsRollback in interface Storage

Overrides:

supportsRollback in class AbstractDatabaseStorage

Returns:

true if transactions are supported

applyCreateScheme

protected java.lang.String applyCreateScheme(java.lang.String tableName,
                                             java.lang.String fieldDefinitions,
                                             java.lang.String parentTableName)

Applies the create scheme (if available), and returns the result (a field type defintiton string)

Overrides:

applyCreateScheme in class AbstractDatabaseStorage

Parameters:

tableName - the table to create

fieldDefinitions - comma separated list of field definitions

parentTableName - the parent table (only used in OO databases)

Returns:

the applied scheme

createSQL

protected java.lang.String createSQL(java.lang.String tableName,
                                     java.lang.String fields,
                                     java.lang.String parentTableName,
                                     java.lang.String parentFields)

Returns the SQL command to use for creating a specified table, optionally extending another supplied table. Overide this method to add a database-specific syntax or optimalization Note that the default implementation uses Ansi SQL and ignores the parentTableName parameter, instead using parentFields to complete the table creation command.

Overrides:

createSQL in class AbstractDatabaseStorage

Parameters:

tableName - the name of the table to create

fields - the definitions of the fields

parentTableName - the name of the parent table. this value is null if the table to be created has no parent table. The table is assumed to exist.

parentFields - the definitions of the fields of the parent table (for use by relational databases)

Returns:

the sql query

dropSQL

protected java.lang.String dropSQL(java.lang.String tableName)

Returns the SQL command to use for dropping a specified table Overide this method to add a database-specific syntax or optimalization

Parameters:

tableName - the name of the table to drop

Returns:

the sql query

insertSQL

protected java.lang.String insertSQL(java.lang.String tableName,
                                     java.lang.String fieldNames,
                                     java.lang.String fieldValues)

Returns the SQL command to use for inserting an object in a table. Overide this method to add a database-specific syntax or optimalization

Overrides:

insertSQL in class AbstractDatabaseStorage

Parameters:

tableName - the name of the table where to insert

fieldNames - the names of the fields to insert

fieldValues - the values (generally '?' tokens that will be replaced) of the fields to insert

Returns:

the sql query

updateSQL

protected java.lang.String updateSQL(java.lang.String tableName,
                                     java.lang.String setFields,
                                     int number)

Returns the SQL command to use for updating an object in a table. Overide this method to add a database-specific syntax or optimalization

Overrides:

updateSQL in class AbstractDatabaseStorage

Parameters:

tableName - the name of the table where to update

setfields - the set-commands for the table fields, generally of the format 'field1=?, field2=? ...'

number - the number of the object to update

Returns:

the sql query

deleteSQL

protected java.lang.String deleteSQL(java.lang.String tableName,
                                     int number)

Returns the SQL command to use for deleting an object in a table. Overide this method to add a database-specific syntax or optimalization

Overrides:

deleteSQL in class AbstractDatabaseStorage

Parameters:

tableName - the name of the table where to delete

number - the number of the object to delete

Returns:

the sql query

selectSQL

protected java.lang.String selectSQL(java.lang.String tableName,
                                     java.lang.String fieldNames,
                                     java.lang.String where,
                                     java.lang.String orderby,
                                     int offset,
                                     int max)

Returns the SQL command to use for selecting data from a table. Overide this method to add a database-specific syntax or optimalization

Overrides:

selectSQL in class AbstractDatabaseStorage

Parameters:

tableName - the name of the table where to update

fieldNames - commaseparated list of fieldnames to retrieve, can be null (retrieve all fields)

where - constraints, can be null (no constraints)

orderby - optional fields to order by, can be null (no order)

offset - offset from where to select records. Note: if you specify an offset larger than 0, you have to specify max

max - maximum number of records, can be -1 (no max)

Returns:

the sql query

isAllowedParentBuilder

public boolean isAllowedParentBuilder(MMObjectBuilder builder)

Returns whether this database support layer allows for builder to be a parent builder (that is, other builders can 'extend' this builder and its database tables). The default behavior is to disallow any object other than "object" or "insrel". Database layers that support other builders should override this mnethod.

Specified by:

isAllowedParentBuilder in interface Storage

Overrides:

isAllowedParentBuilder in class AbstractDatabaseStorage

Parameters:

builder - the builder to test

Returns:

true if the builder can be extended

Since:

MMBase-1.6

setValuePreparedStatement

public boolean setValuePreparedStatement(java.sql.PreparedStatement stmt,
                                         MMObjectNode node,
                                         java.lang.String fieldname,
                                         int i)
                                  throws java.sql.SQLException

Set a prepared statement field i with value of key from the given node.

Specified by:

setValuePreparedStatement in interface DatabaseStorage

Overrides:

setValuePreparedStatement in class AbstractDatabaseStorage

Throws:

java.sql.SQLException - if an error occurred while filling in the fields

loadFieldFromTable

public void loadFieldFromTable(MMObjectNode node,
                               java.lang.String fieldname,
                               java.sql.ResultSet rs,
                               int i)

Stores a field in a table ResultSet in a MMObjectNode.

Specified by:

loadFieldFromTable in interface DatabaseStorage

Overrides:

loadFieldFromTable in class AbstractDatabaseStorage

Parameters:

node - the node to store the field in

fieldname - the name of the field as it is known to MMBase

rs - the ResultSet containing the table row

i - the index of the field in the ResultSet

getText

protected abstract java.lang.String getText(java.lang.String tableName,
                                            java.lang.String fieldname,
                                            int number)

Get text from blob

Overrides:

getText in class Support2Storage

getText

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

Get text from blob

Specified by:

getText in interface Storage

Overrides:

getText in class AbstractDatabaseStorage

Following copied from interface: org.mmbase.storage.Storage

Parameters:

node - the node to retrieve the text from

fieldname - the name of the field to retrieve

Returns:

the retrieved text

getBytes

protected abstract byte[] getBytes(java.lang.String tableName,
                                   java.lang.String fieldname,
                                   int number)

Get bytes from blob

Overrides:

getBytes in class Support2Storage

getBytes

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

Get bytes from blob

Specified by:

getBytes in interface Storage

Overrides:

getBytes in class AbstractDatabaseStorage

Following copied from interface: org.mmbase.storage.Storage

Parameters:

node - the node to retrieve the byte array from

fieldname - the name of the field to retrieve

Returns:

the retrieved byte array

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 in the database tables.

Specified by:

insert in interface Storage

Overrides:

insert in class AbstractDatabaseStorage

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

insertIntoTable

protected int insertIntoTable(MMObjectBuilder builder,
                              MMObjectNode node,
                              DatabaseTransaction trans)
                       throws StorageException

This method inserts a new object in a specified builder table. It performs a simple insert statement (obtained with insertSQL(java.lang.String, java.lang.String, java.lang.String), using the name and fields of the specified builder. Override this method to add required code, such as recursive updates for relational databases. Only fields with states of DBSTATE_PERSISTENT or DBSTATE_SYSTEM are stored in the database tables.

Parameters:

builder - the builder to store the node in. This can be a parentbuilder of the node's actual builder

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,
                      Transaction trans)
               throws StorageException

Commit this node to the specified builder table within a transaction.

Specified by:

commit in interface Storage

Overrides:

commit in class AbstractDatabaseStorage

Parameters:

builder - the builder to commit the node to. This can be a parentbuilder of the node's actual builder

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

commitToTable

protected boolean commitToTable(MMObjectBuilder builder,
                                MMObjectNode node,
                                DatabaseTransaction trans)
                         throws StorageException

Commit the changes to this node to the specified builder table.

Parameters:

builder - the builder to commit the node to. This can be a parentbuilder of the node's actual builder

node - The node to commit

trans - the transaction to perform the insert in

Returns:

true if succesful, false otherwise

Throws:

StorageException - if an error occurred during commit

delete

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

Delete a node within a transaction

Specified by:

delete in interface Storage

Overrides:

delete in class AbstractDatabaseStorage

Parameters:

node - The node to delete

trans - the transaction to perform the insert in

Returns:

true if succesful, false otherwise

Throws:

StorageException - if an error occurred during delete

deleteFromTable

public boolean deleteFromTable(MMObjectBuilder builder,
                               MMObjectNode node,
                               DatabaseTransaction trans)
                        throws StorageException

Remove a node from the specified builder table.

Parameters:

builder - the builder to remove the node from. This can be a parentbuilder of the node's actual builder

node - The node to delete

trans - the transaction to perform the insert in

Returns:

true if succesful, false otherwise

Throws:

StorageException - if an error occurred during delete

getNode

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

Select a node from a specified builder

Specified by:

getNode in interface Storage

Overrides:

getNode in class AbstractDatabaseStorage

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 selection

getNodeType

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

Returns the nodetype for a specified nodereference

Specified by:

getNodeType in interface Storage

Overrides:

getNodeType in class AbstractDatabaseStorage

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

getFieldsOrderCreate

protected java.util.List getFieldsOrderCreate(MMObjectBuilder builder)

Returns the fields of a builder in the order in which they should be created.
Note: order is not of import with this particular database layer, which refers to fields by name (not index). However, older databases DO rely on a specific order of the fields, specifically when inserting data. Also, some older routines in MMBase that still execute SQL on their own (shudder!) access fields on index. Therefor, this supportclass (and extending classes) should make sure the desired order is maintained.

Parameters:

builder - the buidler whose fields to retrieve and sort

Returns:

a list of fields.

getParentBuilder

protected MMObjectBuilder getParentBuilder(MMObjectBuilder builder)

Returns the parent builder of the specifed builder. If the value is null, the builder either has no parent, or its builder is the "object" table, but there was no builder created for this low-level table.

Parameters:

builder - the buidler to find the parent of

Returns:

the parent buidler or null if it cannot be determined

getParentTableName

protected java.lang.String getParentTableName(MMObjectBuilder builder)

Returns the name of the parent table of the specifed builder. If the value is null, the builder has no parent table.

Parameters:

builder - the builder to find the parent of

Returns:

the parent table or null if it has no parent

isParentField

protected boolean isParentField(MMObjectBuilder builder,
                                java.lang.String fieldName)

Tests whether the specified field is a member of the parent table of the specifed builder.

Parameters:

builder - the builder to find the parent of

fieldname - the name to test

Returns:

true if the field belongs to the parent table

create

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

Create a database table for the specified builder.

Specified by:

create in interface Storage

Overrides:

create in class AbstractDatabaseStorage

Parameters:

builder - the builder to create the table for\

trans - the transaction to perform the insert in

Returns:

true if the table was succesfully created

Throws:

StorageException - if an error occurred during create

createObjectStorage

public boolean createObjectStorage(Transaction trans)
                            throws StorageException

Create the object table (the basic table for all objects) within a transaction

Specified by:

createObjectStorage in interface Storage

Overrides:

createObjectStorage in class AbstractDatabaseStorage

Parameters:

trans - the transaction to perform the insert in

Returns:

true if the table was succesfully created

Throws:

StorageException - if an error occurred during create

created

public boolean created(MMObjectBuilder builder)

Tells if a table for the builder already exists

Specified by:

created in interface Storage

Overrides:

created in class AbstractDatabaseStorage

Parameters:

builder - the builder to check

Returns:

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

created

public boolean created(java.lang.String tableName)

Tells if a table already exists

Parameters:

tableName - name of the table to check

Returns:

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

size

public int size(MMObjectBuilder builder)

Return number of objects in a builder

Specified by:

size in interface Storage

Overrides:

size in class AbstractDatabaseStorage

Parameters:

builder - the builder whose objects to count

Returns:

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

size

public int size(java.lang.String tableName)

Return number of entries consisting in given table. If the table does not exist, the function returns -1.

Parameters:

tableName - the table whose records to counted

Returns:

the number of items the table has, or -1 if the table does not exist.

writeBytesToFile

protected boolean writeBytesToFile(java.lang.String filename,
                                   byte[] value)

Writes a byte array to a file.

Parameters:

file - name the path of the file

value - the value to write

Returns:

true if succesful

readBytesFromFile

protected byte[] readBytesFromFile(java.lang.String filename)

Reads a byte array from a file.

Overrides:

readBytesFromFile in class Support2Storage

Parameters:

file - name the path of the file

Returns:

value the value read

drop

public boolean drop(MMObjectBuilder builder)

Drops the table of this builder.

Specified by:

drop in interface Storage

Overrides:

drop in class AbstractDatabaseStorage

Parameters:

builder - the builder whose table to drop

Returns:

true if succesful

addField

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

Adds a field to the table of this builder.

Specified by:

addField in interface Storage

Overrides:

addField in class AbstractDatabaseStorage

Parameters:

builder - the builder whose table 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 table of this builder.

Specified by:

removeField in interface Storage

Overrides:

removeField in class AbstractDatabaseStorage

Parameters:

builder - the builder whose table 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 table of this builder.

Specified by:

changeField in interface Storage

Overrides:

changeField in class AbstractDatabaseStorage

Parameters:

builder - the builder whose table 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.

Specified by:

updateStorage in interface Storage

Overrides:

updateStorage in class AbstractDatabaseStorage

Parameters:

builder - the builder whose table to change

Returns:

true if succesful