Hibernate.orgCommunity Documentation
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Hibernate is designed to operate in many different environments and, as such, there is a broad range of configuration parameters. Fortunately, most have sensible default values and Hibernate is distributed with an examplehibernate.properties file inetc/ that displays the various options. Simply put the example file in your classpath and customize it to suit your needs.
An instance oforg.hibernate.cfg.Configuration represents an entire set of mappings of an application's Java types to an SQL database. Theorg.hibernate.cfg.Configuration is used to build an immutableorg.hibernate.SessionFactory. The mappings are compiled from various XML mapping files.
You can obtain aorg.hibernate.cfg.Configuration instance by instantiating it directly and specifying XML mapping documents. If the mapping files are in the classpath, useaddResource(). For example:
Configuration cfg = new Configuration() .addResource("Item.hbm.xml") .addResource("Bid.hbm.xml");An alternative way is to specify the mapped class and allow Hibernate to find the mapping document for you:
Configuration cfg = new Configuration() .addClass(org.hibernate.auction.Item.class) .addClass(org.hibernate.auction.Bid.class);
Hibernate will then search 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.
Aorg.hibernate.cfg.Configuration also allows you to specify configuration properties. For example:
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. Some alternative options include:
Pass an instance ofjava.util.Properties toConfiguration.setProperties().
Place a file namedhibernate.properties in a root directory of the classpath.
SetSystem properties usingjava -Dproperty=value.
Include<property> elements inhibernate.cfg.xml (this is discussed later).
If you want to get started quicklyhibernate.properties is the easiest approach.
Theorg.hibernate.cfg.Configuration is intended as a startup-time object that will be discarded once aSessionFactory is created.
When all mappings have been parsed by theorg.hibernate.cfg.Configuration, the application must obtain a factory fororg.hibernate.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 oneorg.hibernate.SessionFactory. This is useful if you are using more than one database.
It is advisable to have theorg.hibernate.SessionFactory create and pool JDBC connections for you. If you take this approach, opening aorg.hibernate.Session is as simple as:
Session session = sessions.openSession(); // open a new Session
Once you start a task that requires access to the database, a JDBC connection will be obtained from the pool.
Before you can do this, you first need to pass some JDBC connection properties to Hibernate. All Hibernate property names and semantics are defined on the classorg.hibernate.cfg.Environment. The most important settings for JDBC connection configuration are outlined below.
Hibernate will obtain and pool connections usingjava.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 isnot 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 thehibernate.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 thelib directory. Hibernate will use itsorg.hibernate.connection.C3P0ConnectionProvider for connection pooling if you sethibernate.c3p0.* properties. If you would like to use Proxool, refer to the packagedhibernate.properties and the Hibernate web site for more information.
The following is an examplehibernate.properties file for c3p0:
hibernate.connection.driver_class = org.postgresql.Driverhibernate.connection.url = jdbc:postgresql://localhost/mydatabasehibernate.connection.username = myuserhibernate.connection.password = secrethibernate.c3p0.min_size=5hibernate.c3p0.max_size=20hibernate.c3p0.timeout=1800hibernate.c3p0.max_statements=50hibernate.dialect = org.hibernate.dialect.PostgreSQL82Dialect
For use inside an application server, you should almost always configure Hibernate to obtain connections from an application serverjavax.sql.Datasource registered in JNDI. You will need to set at least one of the following properties:
Table 3.2. Hibernate Datasource Properties
| Property name | Purpose |
|---|---|
| hibernate.connection.datasource | datasource JNDI name |
| hibernate.jndi.url | URL of the JNDI provider (optional) |
| hibernate.jndi.class | class of the JNDIInitialContextFactory (optional) |
| hibernate.connection.username | database user (optional) |
| hibernate.connection.password | database user password (optional) |
Here is an examplehibernate.properties file for an application server provided JNDI datasource:
hibernate.connection.datasource = java:/comp/env/jdbc/testhibernate.transaction.factory_class = \ org.hibernate.transaction.JTATransactionFactoryhibernate.transaction.manager_lookup_class = \ org.hibernate.transaction.JBossTransactionManagerLookuphibernate.dialect = org.hibernate.dialect.PostgreSQL82Dialect
JDBC connections obtained from a JNDI datasource will automatically participate in the container-managed transactions of the application server.
Arbitrary connection properties can be given by prepending "hibernate.connection" to the connection property name. For example, you can specify acharSet connection property usinghibernate.connection.charSet.
You can define your own plugin strategy for obtaining JDBC connections by implementing the interfaceorg.hibernate.connection.ConnectionProvider, and specifying your custom implementation via thehibernate.connection.provider_class property.
There are a number of other properties that control the behavior of Hibernate at runtime. All are optional and have reasonable default values.
Some of these properties are "system-level" only. System-level properties can be set only viajava -Dproperty=value orhibernate.properties. Theycannot be set by the other techniques described above.
Table 3.3. Hibernate Configuration Properties
| Property name | Purpose |
|---|---|
| hibernate.dialect | The classname of a Hibernateorg.hibernate.dialect.Dialect which allows Hibernate to generate SQL optimized for a particular relational database.e.g. In most cases Hibernate will actually be able to choose the correct |
| hibernate.show_sql | Write all SQL statements to console. This is an alternative to setting the log categoryorg.hibernate.SQL todebug.e.g. |
| hibernate.format_sql | Pretty print the SQL in the log and console. e.g. |
| hibernate.default_schema | Qualify unqualified table names with the given schema/tablespace in generated SQL. e.g. |
| hibernate.default_catalog | Qualifies unqualified table names with the given catalog in generated SQL. e.g. |
| hibernate.session_factory_name | Theorg.hibernate.SessionFactory will be automatically bound to this name in JNDI after it has been created.e.g. |
| hibernate.max_fetch_depth | Sets a maximum "depth" for the outer join fetch tree for single-ended associations (one-to-one, many-to-one). A0 disables default outer join fetching.e.g. recommended values between |
| hibernate.default_batch_fetch_size | Sets a default size for Hibernate batch fetching of associations. e.g. recommended values |
| hibernate.default_entity_mode | Sets a default mode for entity representation for all sessions opened from thisSessionFactory, defaults topojo.e.g. |
| hibernate.order_updates | 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. e.g. |
| hibernate.generate_statistics | If enabled, Hibernate will collect statistics useful for performance tuning. e.g. |
| hibernate.use_identifier_rollback | If enabled, generated identifier properties will be reset to default values when objects are deleted. e.g. |
| hibernate.use_sql_comments | If turned on, Hibernate will generate comments inside the SQL, for easier debugging, defaults tofalse.e.g. |
| hibernate.id.new_generator_mappings | Setting is relevant when using@GeneratedValue. It indicates whether or not the newIdentifierGenerator implementations are used forjavax.persistence.GenerationType.AUTO,javax.persistence.GenerationType.TABLE andjavax.persistence.GenerationType.SEQUENCE. Default tofalse to keep backward compatibility.e.g. |
We recommend all new projects which make use of to use@GeneratedValue to also sethibernate.id.new_generator_mappings=true as the new generators are more efficient and closer to the JPA 2 specification semantic. However they are not backward compatible with existing databases (if a sequence or a table is used for id generation).
Table 3.4. Hibernate JDBC and Connection Properties
| Property name | Purpose |
|---|---|
| hibernate.jdbc.fetch_size | A non-zero value determines the JDBC fetch size (callsStatement.setFetchSize()). |
| hibernate.jdbc.batch_size | A non-zero value enables use of JDBC2 batch updates by Hibernate. e.g. recommended values between |
| hibernate.jdbc.batch_versioned_data | Set this property totrue if your JDBC driver returns correct row counts fromexecuteBatch(). It is usually safe to turn this option on. Hibernate will then use batched DML for automatically versioned data. Defaults tofalse.e.g. |
| hibernate.jdbc.factory_class | Select a customorg.hibernate.jdbc.Batcher. Most applications will not need this configuration property.e.g. |
| 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. e.g. |
| hibernate.jdbc.use_streams_for_binary | Use streams when writing/readingbinary orserializable types to/from JDBC.*system-level property*e.g. |
| hibernate.jdbc.use_get_generated_keys | Enables use of JDBC3PreparedStatement.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, it tries to determine the driver capabilities using connection metadata.e.g. |
| hibernate.connection.provider_class | The classname of a customorg.hibernate.connection.ConnectionProvider which provides JDBC connections to Hibernate.e.g. |
| hibernate.connection.isolation | Sets the JDBC transaction isolation level. Checkjava.sql.Connection for meaningful values, but note that most databases do not support all isolation levels and some define additional, non-standard isolations.e.g. |
| hibernate.connection.autocommit | Enables autocommit for JDBC pooled connections (it is not recommended). e.g. |
| 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. For an application server JTA datasource, useafter_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 usingafter_transaction.auto will chooseafter_statement for the JTA and CMT transaction strategies andafter_transaction for the JDBC transaction strategy.e.g. This setting only affects |
| hibernate.connection.<propertyName> | Pass the JDBC property<propertyName> toDriverManager.getConnection(). |
| hibernate.jndi.<propertyName> | Pass the property<propertyName> to the JNDIInitialContextFactory. |
Table 3.5. Hibernate Cache Properties
| Property name | Purpose |
|---|---|
hibernate.cache.provider_class | The classname of a customCacheProvider.e.g. |
hibernate.cache.use_minimal_puts | 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. e.g. |
hibernate.cache.use_query_cache | Enables the query cache. Individual queries still have to be set cachable. e.g. |
hibernate.cache.use_second_level_cache | Can be used to completely disable the second level cache, which is enabled by default for classes which specify a<cache> mapping.e.g. |
hibernate.cache.query_cache_factory | The classname of a customQueryCache interface, defaults to the built-inStandardQueryCache.e.g. |
hibernate.cache.region_prefix | A prefix to use for second-level cache region names. e.g. |
hibernate.cache.use_structured_entries | Forces Hibernate to store data in the second-level cache in a more human-friendly format. e.g. |
hibernate.cache.default_cache_concurrency_strategy | Setting used to give the name of the defaultorg.hibernate.annotations.CacheConcurrencyStrategy to use when either@Cacheable or@Cache is used.@Cache(strategy="..") is used to override this default. |
Table 3.6. Hibernate Transaction Properties
| Property name | Purpose |
|---|---|
hibernate.transaction.factory_class | The classname of aTransactionFactory to use with HibernateTransaction API (defaults toJDBCTransactionFactory).e.g. |
jta.UserTransaction | A JNDI name used byJTATransactionFactory to obtain the JTAUserTransaction from the application server.e.g. |
hibernate.transaction.manager_lookup_class | The classname of aTransactionManagerLookup. It is required when JVM-level caching is enabled or when using hilo generator in a JTA environment.e.g. |
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, seeSection 2.3, “Contextual sessions”. e.g. |
hibernate.transaction.auto_close_session | 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, seeSection 2.3, “Contextual sessions”. e.g. |
Table 3.7. Miscellaneous Properties
| Property name | Purpose |
|---|---|
hibernate.current_session_context_class | Supply a custom strategy for the scoping of the "current"Session. SeeSection 2.3, “Contextual sessions” for more information about the built-in strategies.e.g. |
hibernate.query.factory_class | Chooses the HQL parser implementation. e.g. |
hibernate.query.substitutions | Is used to map from tokens in Hibernate queries to SQL tokens (tokens might be function or literal names, for example). e.g. |
hibernate.hbm2ddl.auto | Automatically validates or exports schema DDL to the database when theSessionFactory is created. Withcreate-drop, the database schema will be dropped when theSessionFactory is closed explicitly.e.g. |
hibernate.hbm2ddl.import_files | Comma-separated names of the optional files containing SQL DML statements executed during the File order matters, the statements of a give file are executed before the statements of the following files. These statements are only executed if the schema is created ie if e.g. |
hibernate.hbm2ddl.import_files_sql_extractor | The classname of a custom e.g. |
hibernate.bytecode.use_reflection_optimizer | Enables the use of bytecode manipulation instead of runtime reflection. This is a System-level property and cannot be set in e.g. |
hibernate.bytecode.provider | Both javassist or cglib can be used as byte manipulation engines; the default is e.g. |
Always set thehibernate.dialect property to the correctorg.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. This means that you will not have to specify 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 8.1 | org.hibernate.dialect.PostgreSQL81Dialect |
| PostgreSQL 8.2 and later | org.hibernate.dialect.PostgreSQL82Dialect |
| MySQL5 | org.hibernate.dialect.MySQL5Dialect |
| MySQL5 with InnoDB | org.hibernate.dialect.MySQL5InnoDBDialect |
| MySQL with MyISAM | org.hibernate.dialect.MySQLMyISAMDialect |
| Oracle (any version) | org.hibernate.dialect.OracleDialect |
| Oracle 9i | org.hibernate.dialect.Oracle9iDialect |
| Oracle 10g | org.hibernate.dialect.Oracle10gDialect |
| Oracle 11g | org.hibernate.dialect.Oracle10gDialect |
| Sybase ASE 15.5 | org.hibernate.dialect.SybaseASE15Dialect |
| Sybase ASE 15.7 | org.hibernate.dialect.SybaseASE157Dialect |
| Sybase Anywhere | org.hibernate.dialect.SybaseAnywhereDialect |
| Microsoft SQL Server 2000 | org.hibernate.dialect.SQLServerDialect |
| Microsoft SQL Server 2005 | org.hibernate.dialect.SQLServer2005Dialect |
| Microsoft SQL Server 2008 | org.hibernate.dialect.SQLServer2008Dialect |
| SAP DB | org.hibernate.dialect.SAPDBDialect |
| Informix | org.hibernate.dialect.InformixDialect |
| HypersonicSQL | org.hibernate.dialect.HSQLDialect |
| H2 Database | org.hibernate.dialect.H2Dialect |
| 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. This is, however, 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 SQLSELECT.
Outer join fetching can be disabledglobally by setting the propertyhibernate.max_fetch_depth to0. A setting of1 or higher enables outer join fetching for one-to-one and many-to-one associations that have been mapped withfetch="join".
SeeSection 20.1, “Fetching strategies” for more information.
Oracle limits the size ofbyte arrays that can be passed to and/or from its JDBC driver. If you wish to use large instances ofbinary orserializable type, you should enablehibernate.jdbc.use_streams_for_binary.This is a system-level setting only.
The properties prefixed byhibernate.cache allow you to use a process or cluster scoped second-level cache system with Hibernate. See theSection 20.2, “The Second Level Cache” for more information.
You can define new Hibernate query tokens usinghibernate.query.substitutions. For example:
hibernate.query.substitutions true=1, false=0
This would cause the tokenstrue andfalse to be translated to integer literals in the generated SQL.
hibernate.query.substitutions toLowercase=LOWER
This would allow you to rename the SQLLOWER function.
If you enablehibernate.generate_statistics, Hibernate exposes a number of metrics that are useful when tuning a running system viaSessionFactory.getStatistics(). Hibernate can even be configured to expose these statistics via JMX. Read the Javadoc of the interfaces inorg.hibernate.stats for more information.
Completely out of date. Hibernate uses JBoss Logging starting in 4.0. This will get documented as we migrate this content to the Developer Guide.
Hibernate utilizesSimple Logging Facade for Java (SLF4J) in order to log various system events. SLF4J can direct your logging output to several logging frameworks (NOP, Simple, log4j version 1.2, JDK 1.4 logging, JCL or logback) depending on your chosen binding. In order to setup logging you will needslf4j-api.jar in your classpath together with the jar file for your preferred binding -slf4j-log4j12.jar in the case of Log4J. See the SLF4Jdocumentation for more detail. To use Log4j you will also need to place alog4j.properties file in your classpath. An example properties file is distributed with Hibernate in thesrc/ directory.
It is recommended 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.internal.ast.AST | Log HQL and SQL ASTs during query parsing |
org.hibernate.secure | Log all JAAS authorization requests |
org.hibernate | Log everything. This is a lot of information but it is useful for troubleshooting |
When developing applications with Hibernate, you should almost always work withdebug enabled for the categoryorg.hibernate.SQL, or, alternatively, the propertyhibernate.show_sql enabled.
The interfaceorg.hibernate.cfg.NamingStrategy allows you to specify a "naming standard" for database objects and schema elements.
You can 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 can specify a different strategy by callingConfiguration.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.
You can configure the persister implementation used to persist your entities and collections:
by default, Hibernate uses persisters that make sense in a relational model and follow Java Persistence's specification
you can define aPersisterClassProvider implementation that provides the persister class used of a given entity or collection
finally, you can override them on a per entity and collection basis in the mapping using@Persister or its XML equivalent
The latter in the list the higher in priority.
You can pass thePersisterClassProvider instance to theConfiguration object.
SessionFactory sf = new Configuration() .setPersisterClassProvider(customPersisterClassProvider) .addAnnotatedClass(Order.class) .buildSessionFactory();
The persister class provider methods, when returning a non null persister class, override the default Hibernate persisters. The entity name or the collection role are passed to the methods. It is a nice way to centralize the overriding logic of the persisters instead of spreading them on each entity or collection mapping.
An alternative approach to configuration is to specify a full configuration in a file namedhibernate.cfg.xml. This file can be used as a replacement for thehibernate.properties file or, if both are present, to override properties.
The XML configuration file is by default expected to be in the root of yourCLASSPATH. Here is an example:
<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://www.hibernate.org/dtd/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 usage="read-write"/> <class-cache usage="read-only"/> <collection-cache collection="org.hibernate.auction.Item.bids" usage="read-write"/> </session-factory></hibernate-configuration>
The advantage of this approach is the externalization of the mapping file names to configuration. Thehibernate.cfg.xml is also more convenient once you have to tune the Hibernate cache. It is your choice to use eitherhibernate.properties orhibernate.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 select 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 compatibleTransactionManager and aResourceManager take care of transaction management (CMT), especially distributed transaction handling across several datasources. You can also demarcate transaction boundaries programmatically (BMT), or you might want to use the optional HibernateTransaction API for this to keep your code portable.
Automatic JNDI binding: Hibernate can bind itsSessionFactory to JNDI after startup.
JTA Session binding: the HibernateSession can be automatically bound to the scope of JTA transactions. Simply lookup theSessionFactory from JNDI and get the currentSession. Let Hibernate manage flushing and closing theSession 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 choose to deploy Hibernate as a managed MBean. This saves you the one line startup code to build yourSessionFactory from aConfiguration. The container will startup yourHibernateService and 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 optionhibernate.connection.aggressive_release to true if your application server shows "connection containment" exceptions.
The HibernateSession API is independent of any transaction demarcation system in your architecture. If you let Hibernate use JDBC directly through a connection pool, you can 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 andUserTransaction when needed.
To keep your code portable between these two (and other) environments we recommend the optional HibernateTransaction API, which wraps and hides the underlying system. You have to specify a factory class forTransaction instances by setting the Hibernate configuration propertyhibernate.transaction.factory_class.
There are three standard, or built-in, choices:
org.hibernate.transaction.JDBCTransactionFactorydelegates to database (JDBC) transactions (default)
org.hibernate.transaction.JTATransactionFactorydelegates to container-managed transactions if an existing transaction is underway in this context (for example, EJB session bean method). Otherwise, a new transaction is started and bean-managed transactions are used.
org.hibernate.transaction.CMTTransactionFactorydelegates to container-managed JTA transactions
You can 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 JTATransactionManager in a managed environment. In an application server, since J2EE does not standardize a single mechanism, you have to specify how Hibernate should obtain a reference to theTransactionManager:
Table 3.10. JTA TransactionManagers
| Transaction Factory | Application Server |
|---|---|
org.hibernate.transaction.JBossTransactionManagerLookup | JBoss AS |
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 |
org.hibernate.transaction.JBossTSStandaloneTransactionManagerLookup | JBoss TS used standalone (ie. outside JBoss AS and a JNDI environment generally). Known to work fororg.jboss.jbossts:jbossjta:4.11.0.Final |
A JNDI-bound HibernateSessionFactory can simplify the lookup function of the factory and create newSessions. This is not, however, related to a JNDI boundDatasource; both simply use the same registry.
If you wish to have theSessionFactory bound to a JNDI namespace, specify a name (e.g.java:hibernate/SessionFactory) using the propertyhibernate.session_factory_name. If this property is omitted, theSessionFactory will not be bound to JNDI. This is especially useful in environments with a read-only JNDI default implementation (in Tomcat, for example).
When binding theSessionFactory to JNDI, Hibernate will use the values ofhibernate.jndi.url,hibernate.jndi.class to instantiate an initial context. If they are not specified, the defaultInitialContext will be used.
Hibernate will automatically place theSessionFactory in JNDI after you callcfg.buildSessionFactory(). This means you will have this call in some startup code, or utility class in your application, unless you use JMX deployment with theHibernateService (this is discussed later in greater detail).
If you use a JNDISessionFactory, an EJB or any other class, you can obtain theSessionFactory using a JNDI lookup.
It is recommended that you bind theSessionFactory to JNDI in a managed environment and use astatic singleton otherwise. To shield your application code from these details, we also recommend to hide the actual lookup code for aSessionFactory in a helper class, such asHibernateUtil.getSessionFactory(). Note that such a class is also a convenient way to startup Hibernate—see chapter 1.
The easiest way to handleSessions and transactions is Hibernate's automatic "current"Session management. For a discussion of contextual sessions seeSection 2.3, “Contextual sessions”. Using the"jta" session context, if there is no HibernateSession associated with the current JTA transaction, one will be started and associated with that JTA transaction the first time you callsessionFactory.getCurrentSession(). TheSessions retrieved viagetCurrentSession() in the"jta" context are set to automatically flush before the transaction completes, close after the transaction completes, and aggressively release JDBC connections after each statement. This allows theSessions to be managed by the life cycle of the JTA transaction to which it is associated, keeping user code clean of such management concerns. Your code can either use JTA programmatically throughUserTransaction, or (recommended for portable code) use the HibernateTransaction API to set transaction boundaries. If you run in an EJB container, declarative transaction demarcation with CMT is preferred.
The linecfg.buildSessionFactory() still has to be executed somewhere to get aSessionFactory into JNDI. You can do this either in astatic initializer block, like the one inHibernateUtil, or you can deploy Hibernate as amanaged service.
Hibernate is distributed withorg.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 examplejboss-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.internal.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 calledMETA-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) can be kept in their own JAR file, but you can 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.