JAVA PERSISTENCE API (JPA)

13.2.1. About JPA

The Java Persistence API (JPA) is the standard for using persistence in Java projects. Java EE 6 applications use the Java Persistence 2.0 specification, documented here: http://www.jcp.org/en/jsr/detail?id=317.
Hibernate EntityManager implements the programming interfaces and life-cycle rules defined by the specification. It provides JBoss EAP 6 with a complete Java Persistence solution.
JBoss EAP 6 is 100% compliant with the Java Persistence 2.0 specification. Hibernate also provides additional features to the specification.
To get started with JPA and JBoss EAP 6, refer to the bean-validation, greeter, and kitchensink quickstarts: Section 1.4.1.1, “Access the Quickstarts”.

13.2.4. Configuration

13.2.4.1. Hibernate Configuration Properties

Table 13.1. Hibernate Java Properties

Property Name	Description
hibernate.dialect	The classname of a Hibernate org.hibernate.dialect.Dialect. Allows Hibernate to generate SQL optimized for a particular relational database. In most cases Hibernate will be able to choose the correct org.hibernate.dialect.Dialect implementation, based on the JDBC metadata returned by the JDBC driver.
hibernate.show_sql	Boolean. Writes all SQL statements to console. This is an alternative to setting the log category org.hibernate.SQL to debug.
hibernate.format_sql	Boolean. Pretty print the SQL in the log and console.
hibernate.default_schema	Qualify unqualified table names with the given schema/tablespace in generated SQL.
hibernate.default_catalog	Qualifies unqualified table names with the given catalog in generated SQL.
hibernate.session_factory_name	The org.hibernate.SessionFactory will be automatically bound to this name in JNDI after it has been created. For example, jndi/composite/name.
hibernate.max_fetch_depth	Sets a maximum "depth" for the outer join fetch tree for single-ended associations (one-to-one, many-to-one). A 0 disables default outer join fetching. The recommended value is between 0 and 3.
hibernate.default_batch_fetch_size	Sets a default size for Hibernate batch fetching of associations. The recommended values are 4, 8, and 16.
hibernate.default_entity_mode	Sets a default mode for entity representation for all sessions opened from this SessionFactory. Values include: dynamic-map, dom4j, pojo.
hibernate.order_updates	Boolean. Forces Hibernate to order SQL updates by the primary key value of the items being updated. This will result in fewer transaction deadlocks in highly concurrent systems.
hibernate.generate_statistics	Boolean. If enabled, Hibernate will collect statistics useful for performance tuning.
hibernate.use_identifier_rollback	Boolean. If enabled, generated identifier properties will be reset to default values when objects are deleted.
hibernate.use_sql_comments	Boolean. If turned on, Hibernate will generate comments inside the SQL, for easier debugging. Default value is false.
hibernate.id.new_generator_mappings	Boolean. This property is relevant when using @GeneratedValue. It indicates whether or not the new IdentifierGenerator implementations are used for javax.persistence.GenerationType.AUTO, javax.persistence.GenerationType.TABLE and javax.persistence.GenerationType.SEQUENCE. Default value is true.
hibernate.ejb.naming_strategy	Chooses the org.hibernate.cfg.NamingStrategy implementation when using Hibernate EntityManager. This class is deprecated and this property is only provided for backward compatibility. This property must not be used with hibernate.ejb.naming_strategy_delegator. If the application does not use EntityManager, follow the instructions here to configure the NamingStrategy: Hibernate Reference Documentation - Implementing a Naming Strategy.
hibernate.ejb.naming_strategy_delegator	Specifies an org.hibernate.cfg.naming.NamingStrategyDelegator implementation for database objects and schema elements when using Hibernate EntityManager. This property has the following possible values. org.hibernate.cfg.naming.LegacyNamingStrategyDelegator: This is the default value. This class is deprecated and is only provided for backward compatibility. org.hibernate.cfg.naming.ImprovedNamingStrategyDelegator: This is the preferred value. It generates default table and column names that comply with the JPA specification. It allows for specification of both the entity and foreign key class names. This class only affects entities that are mapped using Java annotations or JPA XML descriptors. Entities mapped using hbm.xml are not affected, If you prefer, you can configure a custom class that implements org.hibernate.cfg.naming.ImprovedNamingStrategyDelegator NOTE This property must not be used with hibernate.ejb.naming_strategy. It is a temporary replacement for org.hibernate.cfg.NamingStrategy to address its limitations. A more comprehensive solution is planned for Hibernate 5.0 that replaces both org.hibernate.cfg.NamingStrategy and org.hibernate.cfg.naming.NamingStrategyDelegator. If the application does not use EntityManager, follow the instructions here to configure the NamingStrategy: Hibernate Reference Documentation - Implementing a Naming Strategy.

IMPORTANT

For hibernate.id.new_generator_mappings, new applications should keep the default value of true. Existing applications that used Hibernate 3.3.x may need to change it to false to continue using a sequence object or table based generator, and maintain backward compatibility.

13.2.4.2. Hibernate JDBC and Connection Properties

Table 13.2. Properties

Property Name	Description
hibernate.jdbc.fetch_size	A non-zero value that determines the JDBC fetch size (calls Statement.setFetchSize()).
hibernate.jdbc.batch_size	A non-zero value enables use of JDBC2 batch updates by Hibernate. The recommended values are between 5 and 30.
hibernate.jdbc.batch_versioned_data	Boolean. Set this property to true if the JDBC driver returns correct row counts from executeBatch(). Hibernate will then use batched DML for automatically versioned data. Default value is to false.
hibernate.jdbc.factory_class	Select a custom  org.hibernate.jdbc.Batcher. Most applications will not need this configuration property.
hibernate.jdbc.use_scrollable_resultset	Boolean. Enables use of JDBC2 scrollable resultsets by Hibernate. This property is only necessary when using user-supplied JDBC connections. Hibernate uses connection metadata otherwise.
hibernate.jdbc.use_streams_for_binary	Boolean. This is a system-level property. Use streams when writing/reading binary or serializable types to/from JDBC.
hibernate.jdbc.use_get_generated_keys	Boolean. Enables use of JDBC3 PreparedStatement.getGeneratedKeys() to retrieve natively generated keys after insert. Requires JDBC3+ driver and JRE1.4+. Set to false if JDBC driver has problems with the Hibernate identifier generators. By default, it tries to determine the driver capabilities using connection metadata.
hibernate.connection.provider_class	The classname of a custom  org.hibernate.connection.ConnectionProviderwhich provides JDBC connections to Hibernate.
hibernate.connection.isolation	Sets the JDBC transaction isolation level. Check  java.sql.Connection for meaningful values, but note that most databases do not support all isolation levels and some define additional, non-standard isolations. Standard values are 1, 2, 4, 8.
hibernate.connection.autocommit	Boolean. This property is not recommended for use. Enables autocommit for JDBC pooled connections.
hibernate.connection.release_mode	Specifies when Hibernate should release JDBC connections. By default, a JDBC connection is held until the session is explicitly closed or disconnected. The default value auto will choose after_statement for the JTA and CMT transaction strategies, and after_transaction for the JDBC transaction strategy. Available values are auto (default), on_close, after_transaction, after_statement. This setting only affects Session returned from SessionFactory.openSession. For Session obtained through SessionFactory.getCurrentSession, the CurrentSessionContext implementation configured for use controls the connection release mode for that Session.
hibernate.connection.<propertyName>	Pass the JDBC property <propertyName> to DriverManager.getConnection().
hibernate.jndi.<propertyName>	Pass the property <propertyName> to the JNDI InitialContextFactory.

13.2.4.3. Hibernate Cache Properties

Table 13.3. Properties

Property Name	Description
hibernate.cache.region.factory_class	The classname of a custom CacheProvider.
hibernate.cache.use_minimal_puts	Boolean. Optimizes second-level cache operation to minimize writes, at the cost of more frequent reads. This setting is most useful for clustered caches and, in Hibernate3, is enabled by default for clustered cache implementations.
hibernate.cache.use_query_cache	Boolean. Enables the query cache. Individual queries still have to be set cacheable.
hibernate.cache.use_second_level_cache	Boolean. Used to completely disable the second level cache, which is enabled by default for classes that specify a <cache> mapping.
hibernate.cache.query_cache_factory	The classname of a custom QueryCache interface. The default value is the built-in StandardQueryCache.
hibernate.cache.region_prefix	A prefix to use for second-level cache region names.
hibernate.cache.use_structured_entries	Boolean. Forces Hibernate to store data in the second-level cache in a more human-friendly format.
hibernate.cache.default_cache_concurrency_strategy	Setting used to give the name of the default org.hibernate.annotations.CacheConcurrencyStrategy to use when either @Cacheable or @Cache is used. @Cache(strategy="..") is used to override this default.

13.2.4.4. Hibernate Transaction Properties

Table 13.4. Properties

Property Name	Description
hibernate.transaction.factory_class	The classname of a TransactionFactory to use with Hibernate Transaction API. Defaults to JDBCTransactionFactory).
jta.UserTransaction	A JNDI name used by JTATransactionFactory to obtain the JTA UserTransaction from the application server.
hibernate.transaction.manager_lookup_class	The classname of a TransactionManagerLookup. It is required when JVM-level caching is enabled or when using hilo generator in a JTA environment.
hibernate.transaction.flush_before_completion	Boolean. If enabled, the session will be automatically flushed during the before completion phase of the transaction. Built-in and automatic session context management is preferred.
hibernate.transaction.auto_close_session	Boolean. If enabled, the session will be automatically closed during the after completion phase of the transaction. Built-in and automatic session context management is preferred.

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