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6.5 Migration Guide

Table of Contents

This guide discusses migration to Hibernate ORM version 6.5. For migration from earlier versions, see any other pertinent migration guides as well.

Java Time Handling

6.5 adds support for marshalling Java Time objects directly through the JDBC driver as defined by JDBC 4.2. In previous versions, Hibernate would handle Java Time objects using java.sql.Date, java.sql.Time or java.sql.Timestamp references as intermediate forms.

Another behavioral change with this is handling for timezones. OffsetDateTime, OffsetTime and ZonedDateTime all encode explicit timezone information. With direct marshalling, Hibernate simply passes along the value as-is. In the legacy behavior, since the java.sql variants do not encode timezone information, Hibernate generally has to specially handle timezones when converting to those intermediate forms.

For 6.5 this behavior is disabled by default. To opt-in,

hibernate.type.prefer_java_type_jdbc_types=true

It is expected the default will flip for 7.0.

Configurable Query Cache Layout

In Hibernate ORM 6.0 the query cache layout changed from a "shallow" representation of entities and collections, to a "full" representation. This was done to support re-materializing join fetched data from the query cache data without hitting the database. Storing the full data in the query cache leads to a higher memory consumption, which in turn might also hurt application throughput due to a higher garbage collection activity.

6.5 adds the ability to configure the format in which query results are stored in the query cache, either

  • globally via the hibernate.cache.query_cache_layout setting

  • per entity or collection via the @QueryCacheLayout annotation

The global hibernate.cache.query_cache_layout setting defaults to the AUTO value, which will automatically choose SHALLOW or FULL for an entity/collection, depending on whether the entity/collection is cacheable.

Applications that want to retain the FULL cache layout that Hibernate ORM 6.0 used should configure the global property hibernate.cache.query_cache_layout=FULL. Applications that want the cache layout that Hibernate ORM 5 and older versions used should configure the global property hibernate.cache.query_cache_layout=SHALLOW.

Note

Even with the SHALLOW cache layout, the association eagerness implied through join fetches will be respected, and associations will be eagerly initialized. So there is no change of behavior when choosing a different cache layout.

With SHALLOW, Hibernate might need to hit the database to materialize the associated data if it does not exist in the second level cache.

Datatype for enums (H2)

Hibernate ORM 6.5 now uses the ENUM datatype for @Enumerated(EnumType.STRING) enumeration mappings by default on H2, just like ORM 6.2 already started doing for MySQL/MariaDB.

The change is backwards compatible, though schema validation might produce an error now as the expected type is enum, whereas it was varchar of char before. To revert to the original mapping, annotate the enum attribute with @JdbcTypeCode(SqlTypes.VARCHAR) or @Column(columnDefinition = "varchar(255)").

hibernate.boot.allow_jdbc_metadata_access

6.5 adds a new setting named hibernate.boot.allow_jdbc_metadata_access as a supported replacement for the legacy hibernate.temp.use_jdbc_metadata_defaults setting which was only ever considered internal and unsupported for use by applications (as should have been obvious from the name).

This setting controls whether Hibernate should be allowed to access the JDBC DatabaseMetaData during bootstrapping. With this setting enabled (the default), Hibernate will access the DatabaseMetaData to perform some internal configuration based on the reported capabilities of the underlying database. Disabling this setting requires explicit settings for this configuration. At a minimum this includes:

  • hibernate.dialect or jakarta.persistence.database-product-name to indicate the type of database

  • jakarta.persistence.database-product-version to indicate the database version

Validation of Query Result Type

6.5 does more stringent checks that the reported query result type (if one) matches the actual query return type. This will show up as a org.hibernate.TypeMismatchException.

SQL Execution Expectation

6.5 moves away from an enumeration approach to specifying the expected outcome of specific SQL executions to a more extendable approach of directly specifying the Expectation implementation to use. ExecuteUpdateResultCheckStyle and ResultCheckStyle approaches are still available, though deprecated.

The enumerated values are replaced by -

  • org.hibernate.jdbc.Expectation.None

  • org.hibernate.jdbc.Expectation.RowCount

  • org.hibernate.jdbc.Expectation.OutParameter

To update, change e.g.

@SQLInsert(check=ResultCheckStyle.COUNT)

to

@SQLInsert(verify=Expectation.RowCount.class)

Unique Key Naming

Previous 6.x versions did not apply ImplicitNamingStrategy when determining the name of a unique key implicitly.

Annotation Problems

6.5 makes various problems in annotations errors (fail fast) as opposed to logged warnings.

Annotation Processor Rename

The name of Hibernate’s Annotation Processor has been changed to org.hibernate.processor.HibernateProcessor. This change will not affect most users as such processors are normally discovered from the javac "processor path", but is important to know for users using the processor manually.

Jakarta Data

6.5 adds support for the Jakarta Data specification, though this support is considered tech preview as the specification is still being actively developed.

Auto Flush

The auto flush event has been split in two parts a pre-partialFlush and a partialFlush and in order to track the start and the end fo the pre-partialFlush two new methods (void prePartialFlushStart() and void prePartialFlushEnd()) have been added to the SessionEventListener.