Javax.persistence Foreign Key Generator

• Javax Persistence Tutorial
• Javax Persistence Dependency
• Javax.persistence Foreign Key Generator Reviews

• SchemaUpdate javax.persistence.ForeignKey doesn't respect ConstraintMode.NOCONSTRAINT. Unsuccessful: alter table oauthclient add constraint FK43dmxuh3574xhqwmvkt8gdwqf foreign key (owner) references `user` (id) Environment. Jpa2.1 hibernate4.3.0.Final mysql5.6 jdk7.
• SchemaUpdate javax.persistence.ForeignKey doesn't respect ConstraintMode.NOCONSTRAINT. Alter table oauthclient add constraint FK43dmxuh3574xhqwmvkt8gdwqf.

This chapter takes you through the relationships between Entities. Generally the relations are more effective between tables in the database. Here the entity classes are treated as relational tables (concept of JPA), therefore the relationships between Entity classes are as follows: Many-To-One.

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A key serves as a unique identifier for each entity instance. Most entities in EF have a single key, which maps to the concept of a primary key in relational databases (for entities without keys, see Keyless entities). Entities can have additional keys beyond the primary key (see Alternate Keys for more information).

By convention, a property named Id or <type name>Id will be configured as the primary key of an entity.

Note

Owned entity types use different rules to define keys.

You can configure a single property to be the primary key of an entity as follows:

You can also configure multiple properties to be the key of an entity - this is known as a composite key. Composite keys can only be configured using the Fluent API; conventions will never setup a composite key, and you can not use Data Annotations to configure one.

Primary key name

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By convention, on relational databases primary keys are created with the name PK_<type name>. You can configure the name of the primary key constraint as follows:

Javax.persistence Foreign Key Generator Reviews

Key types and values

While EF Core supports using properties of any primitive type as the primary key, including string, Guid, byte[] and others, not all databases support all types as keys. In some cases the key values can be converted to a supported type automatically, otherwise the conversion should be specified manually.

Key properties must always have a non-default value when adding a new entity to the context, but some types will be generated by the database. In that case EF will try to generate a temporary value when the entity is added for tracking purposes. After SaveChanges is called the temporary value will be replaced by the value generated by the database. Openssl generate rsa private key.

Important

If a key property has its value generated by the database and a non-default value is specified when an entity is added, then EF will assume that the entity already exists in the database and will try to update it instead of inserting a new one. To avoid this turn off value generation or see how to specify explicit values for generated properties.

Alternate Keys

An alternate key serves as an alternate unique identifier for each entity instance in addition to the primary key; it can be used as the target of a relationship. When using a relational database this maps to the concept of a unique index/constraint on the alternate key column(s) and one or more foreign key constraints that reference the column(s).

Tip

If you just want to enforce uniqueness on a column, define a unique index rather than an alternate key (see Indexes). In EF, alternate keys are read-only and provide additional semantics over unique indexes because they can be used as the target of a foreign key.

Alternate keys are typically introduced for you when needed and you do not need to manually configure them. By convention, an alternate key is introduced for you when you identify a property which isn't the primary key as the target of a relationship.

You can also configure a single property to be an alternate key:

You can also configure multiple properties to be an alternate key (known as a composite alternate key):

Finally, by convention, the index and constraint that are introduced for an alternate key will be named AK_<type name>_<property name> (for composite alternate keys <property name> becomes an underscore separated list of property names). You can configure the name of the alternate key's index and unique constraint:

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• Packages that use javax.persistence

  Package	Description
  javax.persistence	Java Persistence is the API for the management for persistence and object/relational mapping.
  javax.persistence.criteria
  javax.persistence.spi	SPI for Java Persistence providers

• Classes in javax.persistence used by javax.persistence

  Class	Description
  AccessType	Used with the Access annotation to specify an access type to be applied to an entity class, mapped superclass, or embeddable class, or to a specific attribute of such a class.
  AssociationOverride	Used to override a mapping for an entity relationship.
  AttributeNode
  AttributeOverride	Used to override the mapping of a Basic (whether explicit or default) property or field or Id property or field.
  Cache	Interface used to interact with the second-level cache.
  CacheRetrieveMode	Used as the value of the javax.persistence.cache.retrieveMode property to specify the behavior when data is retrieved by the find methods and by queries.
  CacheStoreMode	Used as the value of the javax.persistence.cache.storeMode property to specify the behavior when data is read from the database and when data is committed into the database.
  CascadeType	Defines the set of cascadable operations that are propagated to the associated entity.
  Column	Specifies the mapped column for a persistent property or field.
  ColumnResult	Used in conjunction with the SqlResultSetMapping annotation or ConstructorResult annotation to map a column of the SELECT list of a SQL query.
  ConstraintMode
  ConstructorResult	Used in conjunction with the SqlResultSetMapping annotation to map the SELECT clause of a SQL query to a constructor.
  Convert	Specifies the conversion of a Basic field or property.
  DiscriminatorType	Defines supported types of the discriminator column.
  EntityGraph	This type represents the root of an entity graph that will be used as a template to define the attribute nodes and boundaries of a graph of entities and entity relationships.
  EntityManager	Interface used to interact with the persistence context.
  EntityManagerFactory	Interface used to interact with the entity manager factory for the persistence unit.
  EntityResult	Used in conjunction with the SqlResultSetMapping annotation to map the SELECT clause of a SQL query to an entity result.
  EntityTransaction	Interface used to control transactions on resource-local entity managers.
  EnumType
  FetchType	Defines strategies for fetching data from the database.
  FieldResult	Used in conjunction with the EntityResult annotation to map columns specified in the SELECT list of a SQL query to the properties or fields of an entity class.
  FlushModeType
  ForeignKey	Used to specify the handling of foreign key constraints when schema generation is in effect.
  GenerationType	Defines the types of primary key generation strategies.
  Index	Used in schema generation to specify creation of an index.
  InheritanceType
  JoinColumn	Specifies a column for joining an entity association or element collection.
  JoinTable
  LockModeType	Lock modes can be specified by means of passing a LockModeType argument to one of the EntityManager methods that take locks (lock, find, or refresh) or to the Query.setLockMode() or TypedQuery.setLockMode() method.
  MapKeyJoinColumn	Specifies a mapping to an entity that is a map key.
  NamedAttributeNode	A NamedAttributeNode is a member element of a NamedEntityGraph.
  NamedEntityGraph	Used to specify the path and boundaries for a find operation or query.
  NamedNativeQuery
  NamedQuery	Specifies a static, named query in the Java Persistence query language.
  NamedStoredProcedureQuery	Specifies and names a stored procedure, its parameters, and its result type.
  NamedSubgraph	A NamedSubgraph is a member element of a NamedEntityGraph.
  Parameter
  ParameterMode	Specifies the mode of a parameter of a stored procedure query.
  PersistenceContext	Expresses a dependency on a container-managed EntityManager and its associated persistence context.
  PersistenceContextType	Specifies whether a transaction-scoped or extended persistence context is to be used in PersistenceContext.
  PersistenceException	Thrown by the persistence provider when a problem occurs.
  PersistenceProperty	Describes a single container or persistence provider property.
  PersistenceUnit	Expresses a dependency on an EntityManagerFactory and its associated persistence unit.
  PersistenceUnitUtil	Utility interface between the application and the persistence provider managing the persistence unit.
  PersistenceUtil	Utility interface between the application and the persistence provider(s).
  PessimisticLockScope	Defines the values of the javax.persistence.lock.scope property for pessimistic locking.
  PrimaryKeyJoinColumn	Specifies a primary key column that is used as a foreign key to join to another table.
  Query
  QueryHint	Used to supply a query property or hint to the NamedQuery or NamedNativeQuery annotation.
  SecondaryTable	Specifies a secondary table for the annotated entity class.
  SequenceGenerator	Defines a primary key generator that may be referenced by name when a generator element is specified for the GeneratedValue annotation.
  SharedCacheMode	Specifies how the provider must use a second-level cache for the persistence unit.
  SqlResultSetMapping	Specifies the mapping of the result of a native SQL query or stored procedure.
  StoredProcedureParameter	Specifies a parameter of a named stored procedure query.
  StoredProcedureQuery	Interface used to control stored procedure query execution.
  Subgraph	This type represents a subgraph for an attribute node that corresponds to a Managed Type.
  SynchronizationType	Specifies whether the persistence context is always automatically synchronized with the current transaction or whether the persistence context must be explicitly joined to the current transaction by means of the EntityManager.joinTransaction() method.
  TableGenerator	Defines a primary key generator that may be referenced by name when a generator element is specified for the GeneratedValue annotation.
  TemporalType	Type used to indicate a specific mapping of java.util.Date or java.util.Calendar.
  TupleElement	The TupleElement interface defines an element that is returned in a query result tuple.
  TypedQuery	Interface used to control the execution of typed queries.
  UniqueConstraint	Specifies that a unique constraint is to be included in the generated DDL for a primary or secondary table.
  ValidationMode	The validation mode to be used by the provider for the persistence unit.

• Classes in javax.persistence used by javax.persistence.criteria

  Class	Description
  Parameter
  Tuple	Interface for extracting the elements of a query result tuple.
  TupleElement	The TupleElement interface defines an element that is returned in a query result tuple.

• Classes in javax.persistence used by javax.persistence.spi

  Class	Description
  EntityManagerFactory	Interface used to interact with the entity manager factory for the persistence unit.
  SharedCacheMode	Specifies how the provider must use a second-level cache for the persistence unit.
  ValidationMode	The validation mode to be used by the provider for the persistence unit.