org.apache.cayenne.dba

Class JdbcPkGenerator

java.lang.Object

org.apache.cayenne.dba.JdbcPkGenerator

All Implemented Interfaces:

PkGenerator

Direct Known Subclasses:

FrontBasePkGenerator, MySQLPkGenerator, OpenBasePkGenerator, OraclePkGenerator, SybasePkGenerator

public class JdbcPkGenerator
extends Object
implements PkGenerator

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

Field Summary

Fields

Modifier and Type	Field and Description
protected JdbcAdapter	adapter
static int	DEFAULT_PK_CACHE_SIZE
protected ConcurrentMap<String,Queue<Long>>	pkCache
protected int	pkCacheSize
protected long	pkStartValue

Constructor Summary

Constructors

Constructor and Description
JdbcPkGenerator(JdbcAdapter adapter)

Method Summary

Modifier and Type	Method and Description
protected boolean	autoPkTableExists(DataNode node) Checks if AUTO_PK_TABLE already exists in the database.
void	createAutoPk(DataNode node, List<DbEntity> dbEntities) Generates necessary database objects to provide automatic primary key support.
List<String>	createAutoPkStatements(List<DbEntity> 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, List<DbEntity> dbEntities) Drops table named "AUTO_PK_SUPPORT" if it exists in the database.
List<String>	dropAutoPkStatements(List<DbEntity> dbEntities) Returns SQL string needed to drop database objects associated with automatic primary key generation.
protected String	dropAutoPkString()
Object	generatePk(DataNode node, DbAttribute pk) Generates a unique and non-repeating primary key for specified dbEntity.
JdbcAdapter	getAdapter()
int	getPkCacheSize() Returns a size of the entity primary key cache.
protected long	longPkFromDatabase(DataNode node, DbEntity entity) Performs primary key generation ignoring cache.
protected String	pkCreateString(String entName)
protected String	pkDeleteString(List<DbEntity> dbEntities)
protected String	pkSelectString(String entName)
protected String	pkTableCreateString()
protected String	pkUpdateString(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, 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

adapter

protected JdbcAdapter adapter

pkCache

protected ConcurrentMap<String,Queue<Long>> pkCache

pkCacheSize

protected int pkCacheSize

pkStartValue

protected long pkStartValue

Constructor Detail

JdbcPkGenerator

public JdbcPkGenerator(JdbcAdapter adapter)

Method Detail

getAdapter

public JdbcAdapter getAdapter()

createAutoPk

public void createAutoPk(DataNode node,
                         List<DbEntity> dbEntities)
                  throws 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 auto-generation support

Throws:

Exception

createAutoPkStatements

public List<String> createAutoPkStatements(List<DbEntity> 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,
                       List<DbEntity> dbEntities)
                throws 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 auto-generation support should be dropped.

Throws:

Exception

dropAutoPkStatements

public List<String> dropAutoPkStatements(List<DbEntity> 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 String pkTableCreateString()

pkDeleteString

protected String pkDeleteString(List<DbEntity> dbEntities)

pkCreateString

protected String pkCreateString(String entName)

pkSelectString

protected String pkSelectString(String entName)

pkUpdateString

protected String pkUpdateString(String entName)

dropAutoPkString

protected String dropAutoPkString()

autoPkTableExists

protected boolean autoPkTableExists(DataNode node)
                             throws SQLException

Checks if AUTO_PK_TABLE already exists in the database.

Throws:

SQLException

runUpdate

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

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

Throws:

SQLException - in case of query failure.

generatePk

public Object generatePk(DataNode node,
                         DbAttribute pk)
                  throws Exception

Generates a 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:

generatePk in interface PkGenerator

Throws:

Exception

Since:

3.0

longPkFromDatabase

protected long longPkFromDatabase(DataNode node,
                                  DbEntity entity)
                           throws 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:

Exception

Since:

3.0

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