org.apache.cayenne.dba
Class JdbcPkGenerator

java.lang.Object
  org.apache.cayenne.dba.JdbcPkGenerator

All Implemented Interfaces:

PkGenerator

Direct Known Subclasses:

DB2PkGenerator, DerbyPkGenerator, FirebirdPkGenerator, FrontBasePkGenerator, MySQLPkGenerator, OpenBasePkGenerator, OraclePkGenerator, SybasePkGenerator

public class JdbcPkGenerator
extends java.lang.Object
implements PkGenerator

Default primary key generator implementation. Uses a lookup table named "AUTO_PK_SUPPORT" to search and increment primary keys for tables.

Author:

Andrei Adamchik

Field Summary

static int	DEFAULT_PK_CACHE_SIZE
protected static java.lang.String	NEXT_ID Deprecated. Since 1.2 unused.
protected static ObjAttribute[]	objDesc Deprecated. Since 1.2 unused.
protected java.util.Map	pkCache
protected int	pkCacheSize
protected static DbAttribute[]	resultDesc Deprecated. Since 1.2 unused.

Constructor Summary

JdbcPkGenerator()

Method Summary

protected boolean	autoPkTableExists(DataNode node) Checks if AUTO_PK_TABLE already exists in the database.
protected byte[]	binaryPK(DbEntity entity)
void	createAutoPk(DataNode node, java.util.List dbEntities) Generates necessary database objects to provide automatic primary key support.
java.util.List	createAutoPkStatements(java.util.List dbEntities) Returns a list of SQL strings needed to generates database objects to provide automatic primary support for the list of entities.
void	dropAutoPk(DataNode node, java.util.List dbEntities) Drops table named "AUTO_PK_SUPPORT" if it exists in the database.
java.util.List	dropAutoPkStatements(java.util.List dbEntities) Returns SQL string needed to drop database objects associated with automatic primary key generation.
protected java.lang.String	dropAutoPkString()
java.lang.Object	generatePkForDbEntity(DataNode node, DbEntity ent) Generates new (unique and non-repeating) primary key for specified dbEntity.
java.lang.String	generatePkForDbEntityString(DbEntity ent) Deprecated. Since 1.2 corresponding interface method is deprecated.
int	getPkCacheSize() Returns a size of the entity primary key cache.
protected java.lang.String	pkCreateString(java.lang.String entName)
protected java.lang.String	pkDeleteString(java.util.List dbEntities)
protected int	pkFromDatabase(DataNode node, DbEntity ent) Performs primary key generation ignoring cache.
protected java.lang.String	pkSelectString(java.lang.String entName)
protected java.lang.String	pkTableCreateString()
protected java.lang.String	pkUpdateString(java.lang.String entName)
void	reset() Resets any cached primary keys forcing generator to go to the database next time id generation is requested.
int	runUpdate(DataNode node, java.lang.String sql) Runs JDBC update over a Connection obtained from DataNode.
void	setPkCacheSize(int pkCacheSize) Sets the size of the entity primary key cache.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_PK_CACHE_SIZE

public static final int DEFAULT_PK_CACHE_SIZE

See Also:

Constant Field Values

NEXT_ID

protected static final java.lang.String NEXT_ID

Deprecated. Since 1.2 unused.

See Also:

Constant Field Values

objDesc

protected static final ObjAttribute[] objDesc

Deprecated. Since 1.2 unused.

resultDesc

protected static final DbAttribute[] resultDesc

Deprecated. Since 1.2 unused.

pkCache

protected java.util.Map pkCache

pkCacheSize

protected int pkCacheSize

Constructor Detail

JdbcPkGenerator

public JdbcPkGenerator()

Method Detail

createAutoPk

public void createAutoPk(DataNode node,
                         java.util.List dbEntities)
                  throws java.lang.Exception

Description copied from interface: PkGenerator

Generates necessary database objects to provide automatic primary key support.

Specified by:

createAutoPk in interface PkGenerator

Parameters:

node - node that provides access to a DataSource.

dbEntities - a list of entities that require primary key autogeneration support

Throws:

java.lang.Exception

createAutoPkStatements

public java.util.List createAutoPkStatements(java.util.List dbEntities)

Description copied from interface: PkGenerator

Returns a list of SQL strings needed to generates database objects to provide automatic primary support for the list of entities. No actual database operations are performed.

Specified by:

createAutoPkStatements in interface PkGenerator

dropAutoPk

public void dropAutoPk(DataNode node,
                       java.util.List dbEntities)
                throws java.lang.Exception

Drops table named "AUTO_PK_SUPPORT" if it exists in the database.

Specified by:

dropAutoPk in interface PkGenerator

Parameters:

node - node that provides access to a DataSource.

dbEntities - a list of entities whose primary key autogeneration support should be dropped.

Throws:

java.lang.Exception

dropAutoPkStatements

public java.util.List dropAutoPkStatements(java.util.List dbEntities)

Description copied from interface: PkGenerator

Returns SQL string needed to drop database objects associated with automatic primary key generation. No actual database operations are performed.

Specified by:

dropAutoPkStatements in interface PkGenerator

pkTableCreateString

protected java.lang.String pkTableCreateString()

pkDeleteString

protected java.lang.String pkDeleteString(java.util.List dbEntities)

pkCreateString

protected java.lang.String pkCreateString(java.lang.String entName)

pkSelectString

protected java.lang.String pkSelectString(java.lang.String entName)

pkUpdateString

protected java.lang.String pkUpdateString(java.lang.String entName)

dropAutoPkString

protected java.lang.String dropAutoPkString()

autoPkTableExists

protected boolean autoPkTableExists(DataNode node)
                             throws java.sql.SQLException

Checks if AUTO_PK_TABLE already exists in the database.

Throws:

java.sql.SQLException

runUpdate

public int runUpdate(DataNode node,
                     java.lang.String sql)
              throws java.sql.SQLException

Runs JDBC update over a Connection obtained from DataNode. Returns a number of objects returned from update.

Throws:

java.sql.SQLException - in case of query failure.

generatePkForDbEntityString

public java.lang.String generatePkForDbEntityString(DbEntity ent)

Deprecated. Since 1.2 corresponding interface method is deprecated.

Description copied from interface: PkGenerator

Returns SQL string that can generate new (unique and non-repeating) primary key for specified DbEntity. No actual database operations are performed.

Specified by:

generatePkForDbEntityString in interface PkGenerator

generatePkForDbEntity

public java.lang.Object generatePkForDbEntity(DataNode node,
                                              DbEntity ent)
                                       throws java.lang.Exception

Generates new (unique and non-repeating) primary key for specified dbEntity.

This implementation is naive since it does not lock the database rows when executing select and subsequent update. Adapter-specific implementations are more robust.

Specified by:

generatePkForDbEntity in interface PkGenerator

ent - DbEntity for which automatic PK is generated.

Throws:

java.lang.Exception

binaryPK

protected byte[] binaryPK(DbEntity entity)

Returns:

a binary PK if DbEntity has a BINARY or VARBINARY pk, null otherwise. This method will likely be deprecated in 1.1 in favor of a more generic soultion.

Since:

1.0.2

pkFromDatabase

protected int pkFromDatabase(DataNode node,
                             DbEntity ent)
                      throws java.lang.Exception

Performs primary key generation ignoring cache. Generates a range of primary keys as specified by "pkCacheSize" bean property.

This method is called internally from "generatePkForDbEntity" and then generated range of key values is saved in cache for performance. Subclasses that implement different primary key generation solutions should override this method, not "generatePkForDbEntity".

Throws:

java.lang.Exception

getPkCacheSize

public int getPkCacheSize()

Returns a size of the entity primary key cache. Default value is 20. If cache size is set to a value less or equals than "one", no primary key caching is done.

setPkCacheSize

public void setPkCacheSize(int pkCacheSize)

Sets the size of the entity primary key cache. If pkCacheSize parameter is less than 1, cache size is set to "one".

Note that our tests show that setting primary key cache value to anything much bigger than 20 does not give any significant performance increase. Therefore it does not make sense to use bigger values, since this may potentially create big gaps in the database primary key sequences in cases like application crashes or restarts.

reset

public void reset()

Description copied from interface: PkGenerator

Resets any cached primary keys forcing generator to go to the database next time id generation is requested. May not be applicable for all generator implementations.

Specified by:

reset in interface PkGenerator