Hibernate.orgCommunity Documentation

Kapitel 3. Konfiguration

3.1. Programmatische Konfiguration
3.2. Erstellung einer SessionFactory
3.3. JDBC-Verbindungen
3.4. Optionale Properties der Konfiguration
3.4.1. SQL-Dialekte
3.4.2. "Outer-Join-Fetching"
3.4.3. Binäre Datenströme
3.4.4. Zweite Ebene und Anfragen-Cache
3.4.5. "Query Language Substitution"
3.4.6. Die Hibernate Statistik
3.5. Protokollierung
3.6. Implementing a NamingStrategy
3.7. XML-Konfigurationsdatei
3.8. Integration des J2EE-Applikationsservers
3.8.1. Konfiguration der Transaktionsstrategie
3.8.2. JNDI-bound SessionFactory
3.8.3. Aktuelles Management des Sessionkontexts mit JTA
3.8.4. JMX-Deployment

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:

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:


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:


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

Von einer JNDI-Datenquelle erhaltene JDBC-Verbindungen nehmen automatisch an den vom Container verwalteten Transaktionen des Applikationsservers teil.

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.

Tabelle 3.3. Konfigurationseigenschaften von Hibernate

Property-NameZweck
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. full.classname.of.Dialect

In most cases Hibernate will actually be able to choose the correct org.hibernate.dialect.Dialect implementation based on the JDBC metadata returned by the JDBC driver.

hibernate.show_sql Schreiben Sie alle SQL-Anweisungen in die Konsole. Es handelt sich dabei um eine Alternative für die Einstellung der Protokollkategorie org.hibernate.SQL auf debug.

e.g. true | false

hibernate.format_sql SQL in Protokoll und Konsole lesbar ausgeben.

e.g. true | false

hibernate.default_schema Qualify unqualified table names with the given schema/tablespace in generated SQL.

e.g. SCHEMA_NAME

hibernate.default_catalog Qualifies unqualified table names with the given catalog in generated SQL.

e.g. CATALOG_NAME

hibernate.session_factory_name The org.hibernate.SessionFactory will be automatically bound to this name in JNDI after it has been created.

e.g. jndi/composite/name

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 0 and 3

hibernate.default_batch_fetch_size Sets a default size for Hibernate batch fetching of associations.

e.g. recommended values 4, 8, 16

hibernate.default_entity_mode Sets a default mode for entity representation for all sessions opened from this SessionFactory

dynamic-map, dom4j, pojo

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. true | false

hibernate.generate_statistics Falls aktiviert, so sammelt Hibernate Statistiken, die bei der Feinabstimmung der Performance von Nutzen sind.

e.g. true | false

hibernate.use_identifier_rollback Falls aktiviert, so werden die generierten Bezeichner-Properties auf die Standardwerte zurückgesetzt, wenn Objekte gelöscht werden.

e.g. true | false

hibernate.use_sql_comments Falls eingeschaltet, generiert Hibernate Kommentare innerhalb der SQL, für eine vereinfachte Fehlersuche. Die Standardeinstellung lautet false.

e.g. true | false


Tabelle 3.4. Hibernate JDBC- und Connection-Properties

Property-NameZweck
hibernate.jdbc.fetch_size Ein Wert ungleich Null bestimmt die Anzahl der JDBC-Datensätze, den so genannten "Fetch Size" (ruft Statement.setFetchSize() auf).
hibernate.jdbc.batch_size Ein Wert von ungleich Null aktiviert die Verwendung von JDBC2-Stapelaktualisierungen (sog. "Batch Updates") durch Hibernate.

e.g. recommended values between 5 and 30

hibernate.jdbc.batch_versioned_data Set this property to true if your JDBC driver returns correct row counts from executeBatch(). It is usually safe to turn this option on. Hibernate will then use batched DML for automatically versioned data. Defaults to false.

e.g. true | false

hibernate.jdbc.factory_class Select a custom org.hibernate.jdbc.Batcher. Most applications will not need this configuration property.

e.g. classname.of.BatcherFactory

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. true | false

hibernate.jdbc.use_streams_for_binary Use streams when writing/reading binary or serializable types to/from JDBC. *system-level property*

e.g. true | false

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. true|false

hibernate.connection.provider_class The classname of a custom org.hibernate.connection.ConnectionProvider which provides JDBC connections to Hibernate.

e.g. classname.of.ConnectionProvider

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. 1, 2, 4, 8

hibernate.connection.autocommit Enables autocommit for JDBC pooled connections (it is not recommended).

e.g. true | false

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. auto (default) | on_close | after_transaction | after_statement

This setting only affects Sessions returned from SessionFactory.openSession. For Sessions obtained through SessionFactory.getCurrentSession, the CurrentSessionContext implementation configured for use controls the connection release mode for those Sessions. See Abschnitt 2.5, „Contextual sessions“

hibernate.connection.<propertyName> Pass the JDBC property <propertyName> to DriverManager.getConnection().
hibernate.jndi.<propertyName> Pass the property <propertyName> to the JNDI InitialContextFactory.




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:


Bei der Entwicklung von Anwendungen mit Hibernate sollten Sie fast ausschließlich mit der aktivierten debug-Einstellung für die Kategorie org.hibernate.SQL arbeiten oder alternativ mit der aktivierten Property hibernate.show_sql.

Das Interface org.hibernate.cfg.NamingStrategy ermöglicht es Ihnen einen Namensgebungsstandard (sog. "naming standard") für Datenbankobjekte und Schema-Elemente zu bestimmen.

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();

Bei org.hibernate.cfg.ImprovedNamingStrategy handelt es sich um eine eingebaute Strategie, die beim Startpunkt einiger Anwendungen von Nutzen sein kann.

Eine andere Konfigurationsmöglichkeit ist die Spezifizierung einer vollständigen Konfigurationsdatei mit dem Namen hibernate.cfg.xml. Diese Datei kann als Ersatz für die hibernate.properties-Datei dienen oder - falls beide vorhanden sind - Properties außer Kraft setzen.

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();

Hibernate besitzt die folgenden Intergrationspunkte für die J2EE Infrastruktur:

Je nach Ihrer Umgebung müssen Sie möglicherweise die Konfigurationsoption hibernate.connection.aggressive_release auf "true" setzen, falls Ihr Server "Connection Containment"-Ausnahmen (d.h. Verbindungseinschränkungen) anzeigt.

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.

Um Ihren Code zwischen diesen beiden (und anderen) Umgebungen übertragbar zu halten, empfehlen wir das optionale Hibernate Transaction-API, welches das zu Grunde liegende System wrappt und verbirgt. Sie müssen eine Factory-Klasse für Transaction-Instanzen bestimmen, indem Sie die Hibernate Konfigurationseigenschaft hibernate.transaction.factory_class einstellen.

There are three standard, or built-in, choices:

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:


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).

Beim Binden der SessionFactory an JNDI, wird Hibernate die Werte von hibernate.jndi.url, hibernate.jndi.class verwenden, um einen Anfangskontext zu initiieren. Werden diese nicht festgelegt, so wird der Standard InitialContext verwendet.

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 Abschnitt 2.5, „Contextual sessions“. Using the "jta" session context, if there is no Hibernate Session associated with the current JTA transaction, one will be started and associated with that JTA transaction the first time you call sessionFactory.getCurrentSession(). The Sessions retrieved via getCurrentSession() in 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.