Chapter 3. Configuration

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.

3.1. Programmatic configuration

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:

  1. Pass an instance of java.util.Properties to Configuration.setProperties().

  2. Place hibernate.properties in a root directory of the classpath.

  3. Set System properties using java -Dproperty=value.

  4. 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.

3.2. Obtaining a SessionFactory

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.

3.3. JDBC connections

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 namePurpose
hibernate.connection.driver_classjdbc driver class
hibernate.connection.urljdbc URL
hibernate.connection.usernamedatabase user
hibernate.connection.passworddatabase user password
hibernate.connection.pool_sizemaximum 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 namePurpose
hibernate.connection.datasourcedatasource JNDI name
hibernate.jndi.urlURL of the JNDI provider (optional)
hibernate.jndi.classclass of the JNDI InitialContextFactory (optional)
hibernate.connection.usernamedatabase user (optional)
hibernate.connection.passworddatabase 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.

3.4. Optional configuration properties

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 namePurpose
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 namePurpose
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 namePurpose
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 namePurpose
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 namePurpose
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

3.4.1. SQL Dialects

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)

RDBMSDialect
DB2org.hibernate.dialect.DB2Dialect
DB2 AS/400org.hibernate.dialect.DB2400Dialect
DB2 OS390org.hibernate.dialect.DB2390Dialect
PostgreSQLorg.hibernate.dialect.PostgreSQLDialect
MySQLorg.hibernate.dialect.MySQLDialect
MySQL with InnoDBorg.hibernate.dialect.MySQLInnoDBDialect
MySQL with MyISAMorg.hibernate.dialect.MySQLMyISAMDialect
Oracle (any version)org.hibernate.dialect.OracleDialect
Oracle 9i/10gorg.hibernate.dialect.Oracle9Dialect
Sybaseorg.hibernate.dialect.SybaseDialect
Sybase Anywhereorg.hibernate.dialect.SybaseAnywhereDialect
Microsoft SQL Serverorg.hibernate.dialect.SQLServerDialect
SAP DBorg.hibernate.dialect.SAPDBDialect
Informixorg.hibernate.dialect.InformixDialect
HypersonicSQLorg.hibernate.dialect.HSQLDialect
Ingresorg.hibernate.dialect.IngresDialect
Progressorg.hibernate.dialect.ProgressDialect
Mckoi SQLorg.hibernate.dialect.MckoiDialect
Interbaseorg.hibernate.dialect.InterbaseDialect
Pointbaseorg.hibernate.dialect.PointbaseDialect
FrontBaseorg.hibernate.dialect.FrontbaseDialect
Firebirdorg.hibernate.dialect.FirebirdDialect

3.4.2. Outer Join Fetching

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.

3.4.3. Binary Streams

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.

3.4.4. Second-level and query cache

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.

3.4.5. Query Language Substitution

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.

3.4.6. Hibernate statistics

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.

3.5. Logging

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

CategoryFunction
org.hibernate.SQLLog all SQL DML statements as they are executed
org.hibernate.typeLog all JDBC parameters
org.hibernate.tool.hbm2ddlLog 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.cacheLog all second-level cache activity
org.hibernate.transactionLog transaction related activity
org.hibernate.jdbcLog all JDBC resource acquisition
org.hibernate.hql.ast.AST Log HQL and SQL ASTs during query parsing
org.hibernate.secureLog 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.

3.6. Implementing a NamingStrategy

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.

3.7. XML configuration file

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();

3.8. J2EE Application Server integration

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.

3.8.1. Transaction strategy configuration

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:

org.hibernate.transaction.JDBCTransactionFactory

delegates to database (JDBC) transactions (default)

org.hibernate.transaction.JTATransactionFactory

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.

org.hibernate.transaction.CMTTransactionFactory

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 FactoryApplication Server
org.hibernate.transaction.JBossTransactionManagerLookupJBoss
org.hibernate.transaction.WeblogicTransactionManagerLookupWeblogic
org.hibernate.transaction.WebSphereTransactionManagerLookupWebSphere
org.hibernate.transaction.WebSphereExtendedJTATransactionLookupWebSphere 6
org.hibernate.transaction.OrionTransactionManagerLookupOrion
org.hibernate.transaction.ResinTransactionManagerLookupResin
org.hibernate.transaction.JOTMTransactionManagerLookupJOTM
org.hibernate.transaction.JOnASTransactionManagerLookupJOnAS
org.hibernate.transaction.JRun4TransactionManagerLookupJRun4
org.hibernate.transaction.BESTransactionManagerLookupBorland ES

3.8.2. JNDI-bound SessionFactory

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.

3.8.3. Current Session context management with JTA

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.

3.8.4. JMX deployment

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.