Because Hibernate is designed to operate in many different environments, there are a large number of configuration parameters. Fortunately, most have sensible default values and Hibernate is distributed with an example hibernate.properties file in etc/ that shows the various options. Just put the example file in your classpath and customize it.
An instance of org.hibernate.cfg.Configuration represents an entire set of mappings of an application's Java types to an SQL database. The Configuration is used to build an (immutable) SessionFactory. The mappings are compiled from various XML mapping files.
You may obtain a Configuration instance by instantiating it directly and specifying XML mapping documents. If the mapping files are in the classpath, use addResource():
Configuration cfg = new Configuration() .addResource("Item.hbm.xml") .addResource("Bid.hbm.xml");
An alternative (sometimes better) way is to specify the mapped class, and let Hibernate find the mapping document for you:
Configuration cfg = new Configuration() .addClass(org.hibernate.auction.Item.class) .addClass(org.hibernate.auction.Bid.class);
Then Hibernate will look for mapping files named /org/hibernate/auction/Item.hbm.xml and /org/hibernate/auction/Bid.hbm.xml in the classpath. This approach eliminates any hardcoded filenames.
A Configuration also allows you to specify configuration properties:
Configuration cfg = new Configuration() .addClass(org.hibernate.auction.Item.class) .addClass(org.hibernate.auction.Bid.class) .setProperty("hibernate.dialect", "org.hibernate.dialect.MySQLInnoDBDialect") .setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/test") .setProperty("hibernate.order_updates", "true");
This is not the only way to pass configuration properties to Hibernate. The various options include:
Pass an instance of java.util.Properties to Configuration.setProperties().
Place hibernate.properties in a root directory of the classpath.
Set System properties using java -Dproperty=value.
Include <property> elements in hibernate.cfg.xml (discussed later).
hibernate.properties is the easiest approach if you want to get started quickly.
The Configuration is intended as a startup-time object, to be discarded once a SessionFactory is created.
When all mappings have been parsed by the Configuration, the application must obtain a factory for Session instances. This factory is intended to be shared by all application threads:
SessionFactory sessions = cfg.buildSessionFactory();
Hibernate does allow your application to instantiate more than one SessionFactory. This is useful if you are using more than one database.
Usually, you want to have the SessionFactory create and pool JDBC connections for you. If you take this approach, opening a Session is as simple as:
Session session = sessions.openSession(); // open a new Session
As soon as you do something that requires access to the database, a JDBC connection will be obtained from the pool.
For this to work, we need to pass some JDBC connection properties to Hibernate. All Hibernate property names and semantics are defined on the class org.hibernate.cfg.Environment. We will now describe the most important settings for JDBC connection configuration.
Hibernate will obtain (and pool) connections using java.sql.DriverManager if you set the following properties:
Table 3.1. Hibernate JDBC Properties
Property name | Purpose |
---|---|
hibernate.connection.driver_class | jdbc driver class |
hibernate.connection.url | jdbc URL |
hibernate.connection.username | database user |
hibernate.connection.password | database user password |
hibernate.connection.pool_size | maximum number of pooled connections |
Hibernate's own connection pooling algorithm is however quite rudimentary. It is intended to help you get started and is not intended for use in a production system or even for performance testing. You should use a third party pool for best performance and stability. Just replace the hibernate.connection.pool_size property with connection pool specific settings. This will turn off Hibernate's internal pool. For example, you might like to use C3P0.
C3P0 is an open source JDBC connection pool distributed along with Hibernate in the lib directory. Hibernate will use its C3P0ConnectionProvider for connection pooling if you set hibernate.c3p0.* properties. If you'd like to use Proxool refer to the packaged hibernate.properties and the Hibernate web site for more information.
Here is an example hibernate.properties file for C3P0:
hibernate.connection.driver_class = org.postgresql.Driver hibernate.connection.url = jdbc:postgresql://localhost/mydatabase hibernate.connection.username = myuser hibernate.connection.password = secret hibernate.c3p0.min_size=5 hibernate.c3p0.max_size=20 hibernate.c3p0.timeout=1800 hibernate.c3p0.max_statements=50 hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
For use inside an application server, you should almost always configure Hibernate to obtain connections from an application server Datasource registered in JNDI. You'll need to set at least one of the following properties:
Table 3.2. Hibernate Datasource Properties
Propery name | Purpose |
---|---|
hibernate.connection.datasource | datasource JNDI name |
hibernate.jndi.url | URL of the JNDI provider (optional) |
hibernate.jndi.class | class of the JNDI InitialContextFactory (optional) |
hibernate.connection.username | database user (optional) |
hibernate.connection.password | database user password (optional) |
Here's an example hibernate.properties file for an application server provided JNDI datasource:
hibernate.connection.datasource = java:/comp/env/jdbc/test hibernate.transaction.factory_class = \ org.hibernate.transaction.JTATransactionFactory hibernate.transaction.manager_lookup_class = \ org.hibernate.transaction.JBossTransactionManagerLookup hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
JDBC connections obtained from a JNDI datasource will automatically participate in the container-managed transactions of the application server.
Arbitrary connection properties may be given by prepending "hibernate.connnection" to the property name. For example, you may specify a charSet using hibernate.connection.charSet.
You may define your own plugin strategy for obtaining JDBC connections by implementing the interface org.hibernate.connection.ConnectionProvider. You may select a custom implementation by setting hibernate.connection.provider_class.
There are a number of other properties that control the behaviour of Hibernate at runtime. All are optional and have reasonable default values.
Warning: some of these properties are "system-level" only. System-level properties can be set only via java -Dproperty=value or hibernate.properties. They may not be set by the other techniques described above.
Table 3.3. Hibernate Configuration Properties
Property name | Purpose |
---|---|
hibernate.dialect |
The classname of a Hibernate Dialect which
allows Hibernate to generate SQL optimized for a particular
relational database.
eg. full.classname.of.Dialect |
hibernate.show_sql |
Write all SQL statements to console. This is an alternative
to setting the log category org.hibernate.SQL
to debug.
eg. true | false |
hibernate.format_sql |
Pretty print the SQL in the log and console.
eg. true | false |
hibernate.default_schema |
Qualify unqualified tablenames with the given schema/tablespace
in generated SQL.
eg. SCHEMA_NAME |
hibernate.default_catalog |
Qualify unqualified tablenames with the given catalog
in generated SQL.
eg. CATALOG_NAME |
hibernate.session_factory_name |
The SessionFactory will be automatically
bound to this name in JNDI after it has been created.
eg. jndi/composite/name |
hibernate.max_fetch_depth |
Set 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.
eg. recommended values between 0 and 3 |
hibernate.default_batch_fetch_size |
Set a default size for Hibernate batch fetching of associations.
eg. recommended values 4, 8, 16 |
hibernate.default_entity_mode |
Set a default mode for entity representation for all sessions
opened from this SessionFactory dynamic-map, dom4j, pojo |
hibernate.order_updates |
Force 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.
eg. true | false |
hibernate.generate_statistics |
If enabled, Hibernate will collect statistics useful for
performance tuning.
eg. true | false |
hibernate.use_identifer_rollback |
If enabled, generated identifier properties will be
reset to default values when objects are deleted.
eg. true | false |
hibernate.use_sql_comments |
If turned on, Hibernate will generate comments inside the SQL, for
easier debugging, defaults to false.
eg. true | false |
Table 3.4. Hibernate JDBC and Connection Properties
Property name | Purpose |
---|---|
hibernate.jdbc.fetch_size | A non-zero value determines the JDBC fetch size (calls Statement.setFetchSize()). |
hibernate.jdbc.batch_size |
A non-zero value enables use of JDBC2 batch updates by Hibernate.
eg. recommended values between 5 and 30 |
hibernate.jdbc.batch_versioned_data |
Set this property to true if your JDBC driver returns
correct row counts from executeBatch() (it is usually
safe to turn this option on). Hibernate will then use batched DML for
automatically versioned data. Defaults to false.
eg. true | false |
hibernate.jdbc.factory_class |
Select a custom Batcher. Most applications
will not need this configuration property.
eg. classname.of.Batcher |
hibernate.jdbc.use_scrollable_resultset |
Enables use of JDBC2 scrollable resultsets by Hibernate.
This property is only necessary when using user supplied
JDBC connections, Hibernate uses connection metadata otherwise.
eg. true | false |
hibernate.jdbc.use_streams_for_binary |
Use streams when writing/reading binary
or serializable types to/from JDBC
(system-level property).
eg. true | false |
hibernate.jdbc.use_get_generated_keys |
Enable use of JDBC3 PreparedStatement.getGeneratedKeys()
to retrieve natively generated keys after insert. Requires JDBC3+ driver
and JRE1.4+, set to false if your driver has problems with the Hibernate
identifier generators. By default, tries to determine the driver capabilites
using connection metadata.
eg. true|false |
hibernate.connection.provider_class |
The classname of a custom ConnectionProvider which provides
JDBC connections to Hibernate.
eg. classname.of.ConnectionProvider |
hibernate.connection.isolation |
Set the JDBC transaction isolation level. Check
java.sql.Connection for meaningful values but
note that most databases do not support all isolation levels.
eg. 1, 2, 4, 8 |
hibernate.connection.autocommit |
Enables autocommit for JDBC pooled connections (not recommended).
eg. true | false |
hibernate.connection.release_mode |
Specify when Hibernate should release JDBC connections. By default,
a JDBC connection is held until the session is explicitly closed or
disconnected. For an application server JTA datasource, you should use
after_statement to aggressively release connections
after every JDBC call. For a non-JTA connection, it often makes sense to
release the connection at the end of each transaction, by using
after_transaction. auto will
choose after_statement for the JTA and CMT transaction
strategies and after_transaction for the JDBC
transaction strategy.
eg. auto (default) | on_close | after_transaction | after_statement Note that this setting only affects Sessions returned from SessionFactory.openSession. For Sessions obtained through SessionFactory.getCurrentSession, the CurrentSessionContext implementation configured for use controls the connection release mode for those Sessions. See Section 2.5, “Contextual Sessions” |
hibernate.connection.<propertyName> | Pass the JDBC property propertyName to DriverManager.getConnection(). |
hibernate.jndi.<propertyName> | Pass the property propertyName to the JNDI InitialContextFactory. |
Table 3.5. Hibernate Cache Properties
Property name | Purpose |
---|---|
hibernate.cache.provider_class |
The classname of a custom CacheProvider.
eg. classname.of.CacheProvider |
hibernate.cache.use_minimal_puts |
Optimize 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.
eg. true|false |
hibernate.cache.use_query_cache |
Enable the query cache, individual queries still have to be set cachable.
eg. true|false |
hibernate.cache.use_second_level_cache |
May be used to completely disable the second level cache, which is enabled
by default for classes which specify a <cache>
mapping.
eg. true|false |
hibernate.cache.query_cache_factory |
The classname of a custom QueryCache interface,
defaults to the built-in StandardQueryCache.
eg. classname.of.QueryCache |
hibernate.cache.region_prefix |
A prefix to use for second-level cache region names.
eg. prefix |
hibernate.cache.use_structured_entries |
Forces Hibernate to store data in the second-level cache
in a more human-friendly format.
eg. true|false |
Table 3.6. Hibernate Transaction Properties
Property name | Purpose |
---|---|
hibernate.transaction.factory_class |
The classname of a TransactionFactory
to use with Hibernate Transaction API
(defaults to JDBCTransactionFactory).
eg. classname.of.TransactionFactory |
jta.UserTransaction |
A JNDI name used by JTATransactionFactory to
obtain the JTA UserTransaction from the
application server.
eg. jndi/composite/name |
hibernate.transaction.manager_lookup_class |
The classname of a TransactionManagerLookup
- required when JVM-level caching is enabled or when using hilo
generator in a JTA environment.
eg. classname.of.TransactionManagerLookup |
hibernate.transaction.flush_before_completion |
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, see
Section 2.5, “Contextual Sessions”.
eg. true | false |
hibernate.transaction.auto_close_session |
If enabled, the session will be automatically closed during the
after completion phase of the transaction. Built-in and
utomatic session context management is preferred, see
Section 2.5, “Contextual Sessions”.
eg. true | false |
Table 3.7. Miscellaneous Properties
Property name | Purpose |
---|---|
hibernate.current_session_context_class |
Supply a (custom) strategy for the scoping of the "current"
Session. See
Section 2.5, “Contextual Sessions” for more
information about the built-in strategies.
eg. jta | thread | managed | custom.Class |
hibernate.query.factory_class |
Chooses the HQL parser implementation.
eg. org.hibernate.hql.ast.ASTQueryTranslatorFactory or org.hibernate.hql.classic.ClassicQueryTranslatorFactory |
hibernate.query.substitutions |
Mapping from tokens in Hibernate queries to SQL tokens
(tokens might be function or literal names, for example).
eg. hqlLiteral=SQL_LITERAL, hqlFunction=SQLFUNC |
hibernate.hbm2ddl.auto |
Automatically validate or export schema DDL to the database
when the SessionFactory is created. With
create-drop, the database schema will be
dropped when the SessionFactory is closed
explicitly.
eg. validate | update | create | create-drop |
hibernate.cglib.use_reflection_optimizer |
Enables use of CGLIB instead of runtime reflection (System-level
property). Reflection can sometimes be useful when troubleshooting,
note that Hibernate always requires CGLIB even if you turn off the
optimizer. You can not set this property in hibernate.cfg.xml.
eg. true | false |
You should always set the hibernate.dialect property to the correct org.hibernate.dialect.Dialect subclass for your database. If you specify a dialect, Hibernate will use sensible defaults for some of the other properties listed above, saving you the effort of specifying them manually.
Table 3.8. Hibernate SQL Dialects (hibernate.dialect)
RDBMS | Dialect |
---|---|
DB2 | org.hibernate.dialect.DB2Dialect |
DB2 AS/400 | org.hibernate.dialect.DB2400Dialect |
DB2 OS390 | org.hibernate.dialect.DB2390Dialect |
PostgreSQL | org.hibernate.dialect.PostgreSQLDialect |
MySQL | org.hibernate.dialect.MySQLDialect |
MySQL with InnoDB | org.hibernate.dialect.MySQLInnoDBDialect |
MySQL with MyISAM | org.hibernate.dialect.MySQLMyISAMDialect |
Oracle (any version) | org.hibernate.dialect.OracleDialect |
Oracle 9i/10g | org.hibernate.dialect.Oracle9Dialect |
Sybase | org.hibernate.dialect.SybaseDialect |
Sybase Anywhere | org.hibernate.dialect.SybaseAnywhereDialect |
Microsoft SQL Server | org.hibernate.dialect.SQLServerDialect |
SAP DB | org.hibernate.dialect.SAPDBDialect |
Informix | org.hibernate.dialect.InformixDialect |
HypersonicSQL | org.hibernate.dialect.HSQLDialect |
Ingres | org.hibernate.dialect.IngresDialect |
Progress | org.hibernate.dialect.ProgressDialect |
Mckoi SQL | org.hibernate.dialect.MckoiDialect |
Interbase | org.hibernate.dialect.InterbaseDialect |
Pointbase | org.hibernate.dialect.PointbaseDialect |
FrontBase | org.hibernate.dialect.FrontbaseDialect |
Firebird | org.hibernate.dialect.FirebirdDialect |
If your database supports ANSI, Oracle or Sybase style outer joins, outer join fetching will often increase performance by limiting the number of round trips to and from the database (at the cost of possibly more work performed by the database itself). Outer join fetching allows a whole graph of objects connected by many-to-one, one-to-many, many-to-many and one-to-one associations to be retrieved in a single SQL SELECT.
Outer join fetching may be disabled globally by setting the property hibernate.max_fetch_depth to 0. A setting of 1 or higher enables outer join fetching for one-to-one and many-to-one associations which have been mapped with fetch="join".
See Section 19.1, “Fetching strategies” for more information.
Oracle limits the size of byte arrays that may be passed to/from its JDBC driver. If you wish to use large instances of binary or serializable type, you should enable hibernate.jdbc.use_streams_for_binary. This is a system-level setting only.
The properties prefixed by hibernate.cache allow you to use a process or cluster scoped second-level cache system with Hibernate. See the Section 19.2, “The Second Level Cache” for more details.
You may define new Hibernate query tokens using hibernate.query.substitutions. For example:
hibernate.query.substitutions true=1, false=0
would cause the tokens true and false to be translated to integer literals in the generated SQL.
hibernate.query.substitutions toLowercase=LOWER
would allow you to rename the SQL LOWER function.
If you enable hibernate.generate_statistics, Hibernate will expose a number of metrics that are useful when tuning a running system via SessionFactory.getStatistics(). Hibernate can even be configured to expose these statistics via JMX. Read the Javadoc of the interfaces in org.hibernate.stats for more information.
Hibernate logs various events using Apache commons-logging.
The commons-logging service will direct output to either Apache Log4j (if you include log4j.jar in your classpath) or JDK1.4 logging (if running under JDK1.4 or above). You may download Log4j from http://jakarta.apache.org. To use Log4j you will need to place a log4j.properties file in your classpath, an example properties file is distributed with Hibernate in the src/ directory.
We strongly recommend that you familiarize yourself with Hibernate's log messages. A lot of work has been put into making the Hibernate log as detailed as possible, without making it unreadable. It is an essential troubleshooting device. The most interesting log categories are the following:
Table 3.9. Hibernate Log Categories
Category | Function |
---|---|
org.hibernate.SQL | Log all SQL DML statements as they are executed |
org.hibernate.type | Log all JDBC parameters |
org.hibernate.tool.hbm2ddl | Log all SQL DDL statements as they are executed |
org.hibernate.pretty | Log the state of all entities (max 20 entities) associated with the session at flush time |
org.hibernate.cache | Log all second-level cache activity |
org.hibernate.transaction | Log transaction related activity |
org.hibernate.jdbc | Log all JDBC resource acquisition |
org.hibernate.hql.ast.AST | Log HQL and SQL ASTs during query parsing |
org.hibernate.secure | Log all JAAS authorization requests |
org.hibernate | Log everything (a lot of information, but very useful for troubleshooting) |
When developing applications with Hibernate, you should almost always work with debug enabled for the category org.hibernate.SQL, or, alternatively, the property hibernate.show_sql enabled.
The interface org.hibernate.cfg.NamingStrategy allows you to specify a "naming standard" for database objects and schema elements.
You may provide rules for automatically generating database identifiers from Java identifiers or for processing "logical" column and table names given in the mapping file into "physical" table and column names. This feature helps reduce the verbosity of the mapping document, eliminating repetitive noise (TBL_ prefixes, for example). The default strategy used by Hibernate is quite minimal.
You may specify a different strategy by calling Configuration.setNamingStrategy() before adding mappings:
SessionFactory sf = new Configuration() .setNamingStrategy(ImprovedNamingStrategy.INSTANCE) .addFile("Item.hbm.xml") .addFile("Bid.hbm.xml") .buildSessionFactory();
org.hibernate.cfg.ImprovedNamingStrategy is a built-in strategy that might be a useful starting point for some applications.
An alternative approach to configuration is to specify a full configuration in a file named hibernate.cfg.xml. This file can be used as a replacement for the hibernate.properties file or, if both are present, to override properties.
The XML configuration file is by default expected to be in the root o your CLASSPATH. Here is an example:
<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <!-- a SessionFactory instance listed as /jndi/name --> <session-factory name="java:hibernate/SessionFactory"> <!-- properties --> <property name="connection.datasource">java:/comp/env/jdbc/MyDB</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="show_sql">false</property> <property name="transaction.factory_class"> org.hibernate.transaction.JTATransactionFactory </property> <property name="jta.UserTransaction">java:comp/UserTransaction</property> <!-- mapping files --> <mapping resource="org/hibernate/auction/Item.hbm.xml"/> <mapping resource="org/hibernate/auction/Bid.hbm.xml"/> <!-- cache settings --> <class-cache class="org.hibernate.auction.Item" usage="read-write"/> <class-cache class="org.hibernate.auction.Bid" usage="read-only"/> <collection-cache collection="org.hibernate.auction.Item.bids" usage="read-write"/> </session-factory> </hibernate-configuration>
As you can see, the advantage of this approach is the externalization of the mapping file names to configuration. The hibernate.cfg.xml is also more convenient once you have to tune the Hibernate cache. Note that is your choice to use either hibernate.properties or hibernate.cfg.xml, both are equivalent, except for the above mentioned benefits of using the XML syntax.
With the XML configuration, starting Hibernate is then as simple as
SessionFactory sf = new Configuration().configure().buildSessionFactory();
You can pick a different XML configuration file using
SessionFactory sf = new Configuration() .configure("catdb.cfg.xml") .buildSessionFactory();
Hibernate has the following integration points for J2EE infrastructure:
Container-managed datasources: Hibernate can use JDBC connections managed by the container and provided through JNDI. Usually, a JTA compatible TransactionManager and a ResourceManager take care of transaction management (CMT), esp. distributed transaction handling across several datasources. You may of course also demarcate transaction boundaries programatically (BMT) or you might want to use the optional Hibernate Transaction API for this to keep your code portable.
Automatic JNDI binding: Hibernate can bind its SessionFactory to JNDI after startup.
JTA Session binding: The Hibernate Session may be automatically bound to the scope of JTA transactions. Simply lookup the SessionFactory from JNDI and get the current Session. Let Hibernate take care of flushing and closing the Session when your JTA transaction completes. Transaction demarcation is either declarative (CMT) or programmatic (BMT/UserTransaction).
JMX deployment: If you have a JMX capable application server (e.g. JBoss AS), you can chose to deploy Hibernate as a managed MBean. This saves you the one line startup code to build your SessionFactory from a Configuration. The container will startup your HibernateService, and ideally also take care of service dependencies (Datasource has to be available before Hibernate starts, etc).
Depending on your environment, you might have to set the configuration option hibernate.connection.aggressive_release to true if your application server shows "connection containment" exceptions.
The Hibernate Session API is independent of any transaction demarcation system in your architecture. If you let Hibernate use JDBC directly, through a connection pool, you may begin and end your transactions by calling the JDBC API. If you run in a J2EE application server, you might want to use bean-managed transactions and call the JTA API and UserTransaction when needed.
To keep your code portable between these two (and other) environments we recommend the optional Hibernate Transaction API, which wraps and hides the underlying system. You have to specify a factory class for Transaction instances by setting the Hibernate configuration property hibernate.transaction.factory_class.
There are three standard (built-in) choices:
delegates to database (JDBC) transactions (default)
delegates to container-managed transaction if an existing transaction is underway in this context (e.g. EJB session bean method), otherwise a new transaction is started and bean-managed transaction are used.
delegates to container-managed JTA transactions
You may also define your own transaction strategies (for a CORBA transaction service, for example).
Some features in Hibernate (i.e. the second level cache, Contextual Sessions with JTA, etc.) require access to the JTA TransactionManager in a managed environment. In an application server you have to specify how Hibernate should obtain a reference to the TransactionManager, since J2EE does not standardize a single mechanism:
Table 3.10. JTA TransactionManagers
Transaction Factory | Application Server |
---|---|
org.hibernate.transaction.JBossTransactionManagerLookup | JBoss |
org.hibernate.transaction.WeblogicTransactionManagerLookup | Weblogic |
org.hibernate.transaction.WebSphereTransactionManagerLookup | WebSphere |
org.hibernate.transaction.WebSphereExtendedJTATransactionLookup | WebSphere 6 |
org.hibernate.transaction.OrionTransactionManagerLookup | Orion |
org.hibernate.transaction.ResinTransactionManagerLookup | Resin |
org.hibernate.transaction.JOTMTransactionManagerLookup | JOTM |
org.hibernate.transaction.JOnASTransactionManagerLookup | JOnAS |
org.hibernate.transaction.JRun4TransactionManagerLookup | JRun4 |
org.hibernate.transaction.BESTransactionManagerLookup | Borland ES |
A JNDI bound Hibernate SessionFactory can simplify the lookup of the factory and the creation of new Sessions. Note that this is not related to a JNDI bound Datasource, both simply use the same registry!
If you wish to have the SessionFactory bound to a JNDI namespace, specify a name (eg. java:hibernate/SessionFactory) using the property hibernate.session_factory_name. If this property is omitted, the SessionFactory will not be bound to JNDI. (This is especially useful in environments with a read-only JNDI default implementation, e.g. Tomcat.)
When binding the SessionFactory to JNDI, Hibernate will use the values of hibernate.jndi.url, hibernate.jndi.class to instantiate an initial context. If they are not specified, the default InitialContext will be used.
Hibernate will automatically place the SessionFactory in JNDI after you call cfg.buildSessionFactory(). This means you will at least have this call in some startup code (or utility class) in your application, unless you use JMX deployment with the HibernateService (discussed later).
If you use a JNDI SessionFactory, an EJB or any other class may obtain the SessionFactory using a JNDI lookup.
We recommend that you bind the SessionFactory to JNDI in a managend environment and use a static singleton otherwise. To shield your application code from these details, we also recommend to hide the actual lookup code for a SessionFactory in a helper class, such as HibernateUtil.getSessionFactory(). Note that such a class is also a convenient way to startup Hibernate—see chapter 1.
The easiest way to handle Sessions and transactions is Hibernates automatic "current" Session management. See the discussion of Section 2.5, “Contextual Sessions”. Using the "jta" session context, if there is no Hibernate Session associated with the current JTA transaction, one will be started and associated with that JTA transaction the first time you call sessionFactory.getCurrentSession(). The Sessions retrieved via getCurrentSession() in "jta" context will be set to automatically flush before the transaction completes, close after the transaction completes, and aggressively release JDBC connections after each statement. This allows the Sessions to be managed by the lifecycle of the JTA transaction to which it is associated, keeping user code clean of such management concerns. Your code can either use JTA programmatically through UserTransaction, or (recommended for portable code) use the Hibernate Transaction API to set transaction boundaries. If you run in an EJB container, declarative transaction demarcation with CMT is preferred.
The line cfg.buildSessionFactory() still has to be executed somewhere to get a SessionFactory into JNDI. You can do this either in a static initializer block (like the one in HibernateUtil) or you deploy Hibernate as a managed service.
Hibernate is distributed with org.hibernate.jmx.HibernateService for deployment on an application server with JMX capabilities, such as JBoss AS. The actual deployment and configuration is vendor specific. Here is an example jboss-service.xml for JBoss 4.0.x:
<?xml version="1.0"?> <server> <mbean code="org.hibernate.jmx.HibernateService" name="jboss.jca:service=HibernateFactory,name=HibernateFactory"> <!-- Required services --> <depends>jboss.jca:service=RARDeployer</depends> <depends>jboss.jca:service=LocalTxCM,name=HsqlDS</depends> <!-- Bind the Hibernate service to JNDI --> <attribute name="JndiName">java:/hibernate/SessionFactory</attribute> <!-- Datasource settings --> <attribute name="Datasource">java:HsqlDS</attribute> <attribute name="Dialect">org.hibernate.dialect.HSQLDialect</attribute> <!-- Transaction integration --> <attribute name="TransactionStrategy"> org.hibernate.transaction.JTATransactionFactory</attribute> <attribute name="TransactionManagerLookupStrategy"> org.hibernate.transaction.JBossTransactionManagerLookup</attribute> <attribute name="FlushBeforeCompletionEnabled">true</attribute> <attribute name="AutoCloseSessionEnabled">true</attribute> <!-- Fetching options --> <attribute name="MaximumFetchDepth">5</attribute> <!-- Second-level caching --> <attribute name="SecondLevelCacheEnabled">true</attribute> <attribute name="CacheProviderClass">org.hibernate.cache.EhCacheProvider</attribute> <attribute name="QueryCacheEnabled">true</attribute> <!-- Logging --> <attribute name="ShowSqlEnabled">true</attribute> <!-- Mapping files --> <attribute name="MapResources">auction/Item.hbm.xml,auction/Category.hbm.xml</attribute> </mbean> </server>
This file is deployed in a directory called META-INF and packaged in a JAR file with the extension .sar (service archive). You also need to package Hibernate, its required third-party libraries, your compiled persistent classes, as well as your mapping files in the same archive. Your enterprise beans (usually session beans) may be kept in their own JAR file, but you may include this EJB JAR file in the main service archive to get a single (hot-)deployable unit. Consult the JBoss AS documentation for more information about JMX service and EJB deployment.