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.
通过java -Dproperty=value来设置系统 (System)属性.
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:
表 3.1. Hibernate JDBC属性
| 属性名 | 用途 |
|---|---|
| hibernate.connection.driver_class | jdbc驱动类 |
| hibernate.connection.url | jdbc URL |
| hibernate.connection.username | 数据库用户 |
| hibernate.connection.password | 数据库用户密码 |
| hibernate.connection.pool_size | 连接池容量上限数目 |
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:
表 3.2. Hibernate数据源属性
| 属性名 | 用途 |
|---|---|
| hibernate.connection.datasource | 数据源JNDI名字 |
| 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从JNDI数据源获得的JDBC连接将自动参与到应用程序服务器中容器管理的事务(container-managed transactions)中去.
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.
java -Dproperty=value or hibernate.properties. They cannot be set by the other techniques described above.
表 3.3. Hibernate配置属性
| 属性名 | 用途 |
|---|---|
| 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 取值 |
| 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_identifer_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. |
表 3.4. Hibernate JDBC和连接(connection)属性
| 属性名 | 用途 |
|---|---|
| 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(). Iit 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. |
表 3.5. Hibernate缓存属性
| 属性名 | 用途 |
|---|---|
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. |
表 3.6. Hibernate事务属性
| 属性名 | 用途 |
|---|---|
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 第 2.5 节 “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 第 2.5 节 “Contextual sessions”. e.g. |
表 3.7. 其他属性
| 属性名 | 用途 |
|---|---|
hibernate.current_session_context_class
| Supply a custom strategy for the scoping of the "current" Session. See 第 2.5 节 “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.cglib.use_reflection_optimizer
| Enables the use of CGLIB instead of runtime reflection (System-level property). Reflection can sometimes be useful when troubleshooting. Hibernate always requires CGLIB even if you turn off the optimizer. You cannot set this property in hibernate.cfg.xml. 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.
表 3.8. Hibernate SQL方言 (hibernate.dialect)
| RDBMS | Dialect |
|---|---|
| DB2 | org.hibernate.dialect.DB2Dialect |
| DB2 AS/400 | org.hibernate.dialect.DB2400Dialect |
| DB2 OS390 | org.hibernate.dialect.DB2390Dialect |
| PostgreSQL | org.hibernate.dialect.PostgreSQLDialect |
| MySQL | org.hibernate.dialect.MySQLDialect |
| MySQL with InnoDB | org.hibernate.dialect.MySQLInnoDBDialect |
| MySQL with MyISAM | org.hibernate.dialect.MySQLMyISAMDialect |
| Oracle (any version) | org.hibernate.dialect.OracleDialect |
| Oracle 9i | org.hibernate.dialect.Oracle9iDialect |
| Oracle 10g | org.hibernate.dialect.Oracle10gDialect |
| Sybase | org.hibernate.dialect.SybaseDialect |
| Sybase Anywhere | org.hibernate.dialect.SybaseAnywhereDialect |
| Microsoft SQL Server | org.hibernate.dialect.SQLServerDialect |
| SAP DB | org.hibernate.dialect.SAPDBDialect |
| Informix | org.hibernate.dialect.InformixDialect |
| HypersonicSQL | org.hibernate.dialect.HSQLDialect |
| Ingres | org.hibernate.dialect.IngresDialect |
| Progress | org.hibernate.dialect.ProgressDialect |
| Mckoi SQL | org.hibernate.dialect.MckoiDialect |
| Interbase | org.hibernate.dialect.InterbaseDialect |
| Pointbase | org.hibernate.dialect.PointbaseDialect |
| FrontBase | org.hibernate.dialect.FrontbaseDialect |
| Firebird | org.hibernate.dialect.FirebirdDialect |
If your database supports ANSI, Oracle or Sybase style outer joins, outer join fetching will often increase performance by limiting the number of round trips to and from the database. 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".
参见第 19.1 节 “抓取策略(Fetching strategies)”获得更多信息.
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 第 19.2 节 “二级缓存（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:
表 3.9. Hibernate日志类别
| 类别 | 功能 |
|---|---|
org.hibernate.SQL | 在所有SQL DML语句被执行时为它们记录日志 |
org.hibernate.type | 为所有JDBC参数记录日志 |
org.hibernate.tool.hbm2ddl | 在所有SQL DDL语句执行时为它们记录日志 |
org.hibernate.pretty | 在session清洗(flush)时，为所有与其关联的实体(最多20个)的状态记录日志 |
org.hibernate.cache | 为所有二级缓存的活动记录日志 |
org.hibernate.transaction | 为事务相关的活动记录日志 |
org.hibernate.jdbc | 为所有JDBC资源的获取记录日志 |
org.hibernate.hql.AST | 在解析查询的时候,记录HQL和SQL的AST分析日志 |
org.hibernate.secure | 为JAAS认证请求做日志 |
org.hibernate | Log everything. This is a lot of information but it is useful for troubleshooting |
在使用Hibernate开发应用程序时, 你应当总是为org.hibernate.SQL 开启debug级别的日志记录,或者开启hibernate.show_sql属性。
org.hibernate.cfg.NamingStrategy接口允许你为数据库中的对象和schema 元素指定一个“命名标准”.
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是一个内建的命名策略, 对 一些应用程序而言，可能是非常有用的起点.
另一个配置方法是在hibernate.cfg.xml文件中指定一套完整的配置. 这个文件可以当成hibernate.properties的替代。 若两个文件同时存在，它将覆盖前者的属性.
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://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>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();针对J2EE体系,Hibernate有如下几个集成的方面:
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.
自动JNDI绑定: Hibernate可以在启动后将 SessionFactory绑定到JNDI.
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).
如果应用程序服务器抛出"connection containment"异常, 根据你的环境，也许该将配置属性 hibernate.connection.release_mode设为after_statement.
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.
为了让你的代码在两种(或其他)环境中可以移植，我们建议使用可选的Hibernate Transaction API, 它包装并隐藏了底层系统. 你必须通过设置Hibernate配置属性hibernate.transaction.factory_class来指定 一个Transaction实例的工厂类.
There are three standard, or built-in, choices:
org.hibernate.transaction.JDBCTransactionFactory委托给数据库(JDBC)事务（默认）
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.CMTTransactionFactory委托给容器管理的JTA事务
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:
表 3.10. JTA TransactionManagers
| Transaction工厂类 | 应用程序服务器 |
|---|---|
org.hibernate.transaction.JBossTransactionManagerLookup | JBoss |
org.hibernate.transaction.WeblogicTransactionManagerLookup | Weblogic |
org.hibernate.transaction.WebSphereTransactionManagerLookup | WebSphere |
org.hibernate.transaction.WebSphereExtendedJTATransactionLookup | WebSphere 6 |
org.hibernate.transaction.OrionTransactionManagerLookup | Orion |
org.hibernate.transaction.ResinTransactionManagerLookup | Resin |
org.hibernate.transaction.JOTMTransactionManagerLookup | JOTM |
org.hibernate.transaction.JOnASTransactionManagerLookup | JOnAS |
org.hibernate.transaction.JRun4TransactionManagerLookup | JRun4 |
org.hibernate.transaction.BESTransactionManagerLookup | Borland ES |
A JNDI-bound Hibernate SessionFactory can simplify the lookup function of the factory and create new Sessions. 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).
在将SessionFactory绑定至JNDI时, Hibernate将使用hibernate.jndi.url, 和hibernate.jndi.class的值来实例化初始环境(initial context). 如果它们没有被指定, 将使用默认的InitialContext.
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 Hibernatesee chapter 1.
The easiest way to handle Sessions and transactions is Hibernate's automatic "current" Session management. For a discussion of contextual sessions see 第 2.5 节 “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 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 Sessions 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.
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