hibernate-orm/design/type-system-mapping.adoc

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= Mapping model
[plantuml,SqmTypeSystem,png]
.Mapping type system
....
@startuml
skinparam handwritten true
interface MappingType
interface ValueMapping
interface BasicType
interface ModelPart
interface ModelPartContainer
MappingType <|--
ValueMapping <|-- BasicType
ValueMapping <|-- ModelPart
ModelPartContainer <|-- EntityMapping
ModelPartContainer <|-- EmbeddableMapping
ModelPart <|-- EmbeddableMapping
ModelPart <|-- AttributeMapping
ModelPart <|-- EntityIdentifierMapping
ModelPart <|-- EntityVersionMapping
ModelPart <|-- EntityDiscriminatorMapping
@enduml
....
[source,JAVA]
----
interface ValueMapping {
Type getMappingType();
<X> X getCapability(Class<X> capabilityType);
...
}
interface ModelPart extends ValueMapping {
<T> DomainResult<T> createDomainResult(...);
void applySqlSelections(...);
...
}
interface ModelPartContainer extends ValueMapping {
void visitSubMappings(Consumer<ModelPart> action);
ModelPart findSubPart(String name);
ModelPart resolveSubPart(String path);
}
interface EntityMapping extends ModelPartContainer {
default EntityPersister getEntityPersister() {
return getCapability( EntityPersister.class );
}
default EntityIdentifierMapping getIdentifierMapping() {
return getCapability( EntityIdentifierMapping.class );
}
default EntityVersionMapping getVersionMapping() {
return getCapability( EntityVersionMapping.class );
}
default EntityDiscriminatorMapping getDiscriminatorMapping() {
return getCapability( EntityDiscriminatorMapping.class );
}
...
}
interface EmbeddableMapping extends ModelPart, ModelPartContainer {
...
}
----
== Relationship with legacy "persister walking" SPI
`org.hibernate.metamodel.model.mapping` contract corollaries in `org.hibernate.persister.walking`:
EntityMapping::EntityDefinition
EmbeddableMapping::CompositionDefinition
AttributeMapping::AttributeDefinition
EntityIdentifierMapping::EntityIdentifierDefinition
== AllowableParameterType
`AllowableParameterType` is a contract that defines types that are valid for parameter binding in terms of an SQM query.
AT some point this needs to be "resolved" to a ValueMapping/Type/Bindable when generating the SQL AST and executing.
One option is to have the `AllowableParameterType` be resolved first to a `SqmExpressable`
`SqmExpressableAllowableParameterType#resolveSqmExpressable`