Hibernate.orgCommunity Documentation
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
example hibernate.properties
file in
etc/
that displays the various options. Simply put the
example file in your classpath and customize it to suit your needs.
An instance of
org.hibernate.cfg.Configuration
represents an
entire set of mappings of an application's Java types to an SQL database.
The org.hibernate.cfg.Configuration
is used to
build an immutable
org.hibernate.SessionFactory
. The mappings
are compiled from various XML mapping files.
You can obtain a
org.hibernate.cfg.Configuration
instance by
instantiating it directly and specifying XML mapping documents. If the
mapping files are in the classpath, use addResource()
.
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.
A org.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 of java.util.Properties
to Configuration.setProperties()
.
Place a file named hibernate.properties
in
a root directory of the classpath.
Set System
properties using java
-Dproperty=value
.
Include <property>
elements in
hibernate.cfg.xml
(this is discussed later).
If you want to get started
quicklyhibernate.properties
is the easiest
approach.
The org.hibernate.cfg.Configuration
is
intended as a startup-time object that will be discarded once a
SessionFactory
is created.
When all mappings have been parsed by the
org.hibernate.cfg.Configuration
, the application
must obtain a factory for
org.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 one
org.hibernate.SessionFactory
. This is
useful if you are using more than one database.
It is advisable to have the
org.hibernate.SessionFactory
create and
pool JDBC connections for you. If you take this approach, opening a
org.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 class org.hibernate.cfg.Environment
.
The most important settings for JDBC connection configuration are outlined
below.
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 org.hibernate.connection.C3P0ConnectionProvider
for connection pooling if you set hibernate.c3p0.*
properties. If you would like to use Proxool, refer to the packaged
hibernate.properties
and the Hibernate web site for
more information.
The following 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
javax.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 JNDI
InitialContextFactory
(optional) |
hibernate.connection.username | database user (optional) |
hibernate.connection.password | database user password (optional) |
Here is 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 can be given by prepending
"hibernate.connection
" to the connection property name.
For example, you can specify a charSet connection
property using hibernate.connection.charSet.
You can define your own plugin strategy for obtaining JDBC
connections by implementing the interface
org.hibernate.connection.ConnectionProvider
,
and specifying your custom implementation via the
hibernate.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 via
java -Dproperty=value
or
hibernate.properties
. They
cannot be set by the other techniques described
above.
Table 3.3. Hibernate Configuration Properties
Property name | Purpose |
---|---|
hibernate.dialect | The classname of a Hibernate
org.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 category org.hibernate.SQL
to debug . 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 | The
org.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). A
0 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 this SessionFactory
|
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 to false .
e.g.
|
hibernate.id.new_generator_mappings | Setting is relevant when using
@GeneratedValue . It indicates whether or
not the new IdentifierGenerator
implementations are used for
javax.persistence.GenerationType.AUTO ,
javax.persistence.GenerationType.TABLE and
javax.persistence.GenerationType.SEQUENCE .
Default to false to keep backward
compatibility. e.g.
|
We recommend all new projects which make use of to use
@GeneratedValue
to also set
hibernate.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 (calls
Statement.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 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 .
e.g. |
hibernate.jdbc.factory_class | Select a custom
org.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/reading binary
or serializable types to/from JDBC.
*system-level property* e.g. |
hibernate.jdbc.use_get_generated_keys | Enables 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, it tries to
determine the driver capabilities using connection metadata.
e.g.
|
hibernate.connection.provider_class | The classname of a custom
org.hibernate.connection.ConnectionProvider
which provides JDBC connections to Hibernate. e.g.
|
hibernate.connection.isolation | Sets the JDBC transaction isolation level. Check
java.sql.Connection for meaningful
values, but note that most databases do not support all isolation
levels and some define additional, non-standard isolations.
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, 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. e.g. This setting
only affects |
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 .
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 custom QueryCache
interface, defaults to the built-in
StandardQueryCache . 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 default
org.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 a TransactionFactory to
use with Hibernate Transaction API (defaults to
JDBCTransactionFactory ). e.g.
|
jta.UserTransaction | A JNDI name used by
JTATransactionFactory to obtain the JTA
UserTransaction from the application server.
e.g.
|
hibernate.transaction.manager_lookup_class | The classname of a
TransactionManagerLookup . It is required when
JVM-level caching is enabled or when using hilo generator in a JTA
environment. 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, see Section 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, see Section 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 . See Section 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 the SessionFactory is created.
With create-drop , the database schema will be
dropped when the SessionFactory 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.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 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. 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 | org.hibernate.dialect.PostgreSQLDialect |
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 | org.hibernate.dialect.SybaseASE15Dialect |
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 SQL
SELECT
.
Outer join fetching can 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
that have been mapped with fetch="join"
.
See Section 21.1, “Fetching strategies” for more information.
Oracle limits the size of byte
arrays that can
be passed to and/or 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 21.2, “The Second Level Cache” for more
information.
You can define new Hibernate query tokens using
hibernate.query.substitutions
. For example:
hibernate.query.substitutions true=1, false=0
This would cause the tokens true
and
false
to be translated to integer literals in the
generated SQL.
hibernate.query.substitutions toLowercase=LOWER
This would allow you to rename the SQL LOWER
function.
If you enable hibernate.generate_statistics
,
Hibernate exposes 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 utilizes Simple 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 need
slf4j-api.jar
in your classpath together with the jar
file for your preferred binding - slf4j-log4j12.jar
in the case of Log4J. See the SLF4J documentation for more
detail. To use Log4j you will also need to place a
log4j.properties
file in your classpath. An example
properties file is distributed with Hibernate in the
src/
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.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 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 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 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.
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 a PersisterClassProvider
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 the PersisterClassProvider
instance to the Configuration
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 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
of your CLASSPATH
. 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 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>
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. It 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 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 compatible TransactionManager
and a ResourceManager
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
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
can be automatically bound to the scope of
JTA transactions. Simply lookup the SessionFactory
from JNDI and get the current Session
. Let
Hibernate manage 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 choose 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 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 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 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, or built-in, choices:
org.hibernate.transaction.JDBCTransactionFactory
delegates to database (JDBC) transactions (default)
org.hibernate.transaction.JTATransactionFactory
delegates 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.CMTTransactionFactory
delegates 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 JTA
TransactionManager
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 the
TransactionManager
:
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 for
org.jboss.jbossts:jbossjta:4.11.0.Final |
A JNDI-bound Hibernate SessionFactory
can
simplify the lookup function of the factory and create new
Session
s. This is not, however, 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 (e.g.
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 (in Tomcat, for example).
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 have
this call in some startup code, or utility class in your application,
unless you use JMX deployment with the
HibernateService
(this is discussed later in greater
detail).
If you use a JNDI SessionFactory
, an EJB or any
other class, you can obtain the SessionFactory
using
a JNDI lookup.
It is recommended that you bind the
SessionFactory
to JNDI in a managed 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 Hibernate's automatic "current"
Session
management. For a discussion of contextual
sessions see Section 2.3, “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
Session
s retrieved via
getCurrentSession()
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 the
Session
s 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
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 can
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) 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.
Copyright © 2004 Red Hat, Inc.