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hibernate-orm/working-5.0-migration-guide.md

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Working list of changes for 5.0

  • Switch from Configuration to ServiceRegistry+Metadata for SessionFactory building
  • org.hibernate.hql.spi.MultiTableBulkIdStrategy#prepare contract has been changed to account for Metadata
  • (proposed) org.hibernate.persister.spi.PersisterFactory contract, specifically building CollectionPersisters) has been changed to account for Metadata
  • extract org.hibernate.engine.jdbc.env.spi.JdbcEnvironment from JdbcServices; create org.hibernate.engine.jdbc.env package and moved a few contracts there.
  • Introduction of org.hibernate.boot.model.relational.ExportableProducer which will effect any org.hibernate.id.PersistentIdentifierGenerator implementations
  • Change to signature of org.hibernate.id.Configurable to accept JdbcEnvironment rather than just Dialect
  • Removed deprecated org.hibernate.id.TableGenerator id-generator
  • Removed deprecated org.hibernate.id.TableHiLoGenerator (hilo) id-generator
  • Deprecated org.hibernate.id.SequenceGenerator and its subclasses
  • cfg.xml files are again fully parsed and integrated (events, security, etc)
  • Removed the deprecated org.hibernate.cfg.AnnotationConfiguration
  • Integrator contract
  • Configuration is no longer Serializable
  • org.hibernate.dialect.Dialect.getQuerySequencesString expected to retrieve catalog, schema, and increment values as well
  • properties loaded from cfg.xml through EMF did not previously prefix names with "hibernate." this is now made consistent.
  • removed AuditConfiguration in preference for new org.hibernate.envers.boot.internal.EnversService
  • changed AuditStrategy method parameters from (removed) AuditConfiguration to (new) EnversService
  • Built-in org.hibernate.type.descriptor.sql.SqlTypeDescriptor implementations no longer auto-register themselves with org.hibernate.type.descriptor.sql.SqlTypeDescriptorRegistry. Applications using custom SqlTypeDescriptor implementations extending the built-in ones and relying on that behavior should be updated to call SqlTypeDescriptorRegistry#addDescriptor themselves.

TODOs

  • Still need to go back and make all "persistent id generators" to properly implement ExportableProducer
  • Add a setting to "consistently apply" naming strategies. E.g. use the "join column" methods from hbm.xml binding.
  • Along with this ^^ consistency setting, split the implicit naming strategy for join columns into multiple methods - one for each usage:
    • many-to-one
    • one-to-one
    • etc

Blog items

  • New bootstrapping API - better determinism, better integration
  • Java 8 Support (though still compatible with Java 6).
  • Ability to handle additional Java types for id attributes marked as GenerationType#AUTO. Built-in support for Number and UUID. Expandable via new org.hibernate.boot.model.IdGeneratorStrategyInterpreter extension
  • Expanded support for AttributeConverters.
    • fully supported for non-@Enumerated enum values
    • applicable in conjunction with @Nationalized support
    • called to handle null values
    • settable in hbm.xml by using type="converter:fully.qualified.AttributeConverterName"
    • integrated with hibernate-envers
    • collection values, map keys
  • scanning support for non-JPA usage
  • naming strategy

Proposals for discussion

  • Currently there is a "post-binding" hook to allow validation of the bound model (PersistentClass, Property, Value, etc). However, the top-level entry points are currently the only possible place (per contract) to throw exceptions when a validation fails". I'd like to instead consider a pattern where each level is asked to validate itself. Given the current model, however, this is unfortunately not a win-win situation. org.hibernate.boot.model.source.internal.hbm.ModelBinder#createManyToOneAttribute illustrates one such use case where this would be worthwhile, and also can illustrate how pushing the validation (and exception throwing down) can be less than stellar given the current model. In the process of binding a many-to-one, we need to validate that any many-to-one that defines "delete-orphan" cascading is a "logical one-to-one". There are 2 ways a many-to-one can be marked as a "logical one-to-one"; first is at the <many-to-one/> level; the other is through a singular <column/> that is marked as unique. Occasionally the binding of the column(s) of a many-to-one need to be delayed until a second pass, which means that sometimes we cannot perform this check immediately from the #createManyToOneAttribute method. What would be ideal would be to check this after all binding is complete. In current code, this could be either an additional SecondPass or done in a ManyToOne#isValid override of SimpleValue#isValid. The ManyToOne#isValid approach illustrates the conundrum... In the ManyToOne#isValid call we know the real reason the validation failed (non-unique many-to-one marked for orphan delete) but not the property name/path. Simply returning false from ManyToOne#isValid would instead lead to a misleading exception message, which would at least have the proper context to know the property name/path.
  • Should org.hibernate.boot.MetadataBuilder be folded into org.hibernate.boot.MetadataSources?
  • Consider an additional "naming strategy contract" specifically for logical naming. This would be non-pluggable, and would be the thing that generates the names we use to cross-reference and locate tables, columns, etc.