Jpa Composite Key Sequence Generator
- Jpa Composite Key Sequence Generator For Sale
- Sql Composite Key Example
- Jpa Composite Key Sequence Generator Reviews
- Sequence Generator Composite Key Jpa
- Foreign Key
- Jpa Id Generator
Every JPA entity must have a primary key.
You can specify a primary key as a single primitive, or JDK object type entity field (see 'Configuring a JPA Entity Simple Primary Key Field').
You can specify a composite primary key made up of one or more primitive, or JDK object types using a separate composite primary key class (see 'Configuring a JPA Entity Composite Primary Key Class').
Sep 04, 2017 Although not a very common mapping, you can map a composite identifier where one of the Primary Key columns is auto-generated. While for a SEQUENCE identifier, we can use the JPA specification, for IDENTITY, we need to use the Hibernate-specific @SQLInsert annotation. Nevertheless, this mapping is possible when using Hibernate. In this tutorial, you will learn primary key generation strategies in JPA/Hibernate. Identifiers represent the primary key of an entity and they uniquely identify each entity. I am hoping, you have a good understanding of Entity Mapping. Hibernate and JPA assumes that the field annotated with @Id is. UNIQUE – The value in the DB table is unique. JPA and Hibernate can do much more than just mapping a numerical primary key column to an entity attribute. You can use them to generate unique primary key values, to map and create UUIDs, to work with composite primary keys, and to use the same primary key value for associated entities.
Jpa Composite Key Sequence Generator For Sale
You can either assign primary key values yourself, or you can associate a primary key field with a primary key value generator (see 'Configuring JPA Entity Automatic Primary Key Generation').
Configuring a JPA Entity Simple Primary Key Field
The simplest primary key is one you specify as a single primitive or JDK object type entity field (see 'Using Annotations').
Note:
For a JPA entity primary key field code example, see:http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtoejb30mappingannotations/doc/how-to-ejb30-mapping-annotations.html#id
Using Annotations
Example 7-1 shows how to use the @Id
annotation to specify an entity field as the primary key. In this example, primary key values are generated using a table generator (see 'Configuring JPA Entity Automatic Primary Key Generation').
Configuring a JPA Entity Composite Primary Key Class
A composite primary key is usually made up of two or more primitive or JDK object types. Composite primary keys typically arise when mapping from legacy databases when the database key is comprised of several columns. You can specify such a composite primary key with a separate composite primary key class (see 'Using Annotations')
A composite primary key class has the following characteristics:
It is a POJO class.
It must be public and must have a public no-argument constructor.
If you use property-based access, the properties of the primary key class must be public or protected.
It must be serializable.
It must define
equals
andhashCode
methods.The semantics of value equality for these methods must be consistent with the database equality for the database types to which the key is mapped.
You can make the composite primary key class either an embedded class owned by the entity class, or a nonembedded class whose fields you map to multiple fields or properties of the entity class. In the latter case, the names of primary key fields or properties in the composite primary key class and those of the entity class must correspond and their types must be the same.
Using Annotations
Sql Composite Key Example
Example 7-2 shows a typical embeddable composite primary key class. Example 7-3 shows how to configure a JPA entity with this embedded composite primary key class using the @EmbeddedId
annotation.
Example 7-2 Embeddable Composite Primary Key Class
Example 7-3 JPA Entity With an Embedded Composite Primary Key Class
Example 7-5 shows a nonembedded composite primary key class. In this class, fields empName
and birthDay
must correspond in name and type to properties in the entity class. Example 7-5 shows how to configure a JPA entity with this nonembedded composite primary key class using the @IdClass
annotation. Because entity class fields empName
and birthDay
are used in the primary key, you must also annotate them using the @Id
annotation.
Example 7-4 Non-Embedded Composite Primary Key Class
Example 7-5 JPA Entity With a Mapped Composite Primary Key Class
Configuring JPA Entity Automatic Primary Key Generation
Typically, you associate a primary key field (see 'Configuring a JPA Entity Simple Primary Key Field') with a primary key value generator so that when an entity instance is created, a new, unique primary key value is assigned automatically.
Table 7-2 lists the types of primary key value generators that you can define.
Table 7-2 JPA Entity Primary Key Value Generators
Type | Description | For more information, see .. |
---|---|---|
Generated Id Table | A database table that the container uses to store generated primary key values for entities. Typically shared by multiple entity types that use table-based primary key generation. Each entity type will typically use its own row in the table to generate the primary key values for that entity class. Primary key values are positive integers. | 'Table Sequencing' in the Oracle TopLink Developer's GuideMicrosoft office 2007 standard product key generator. |
Table Generator | A primary key generator, which you can reference by name, defined at one of the package, class, method, or field level. The level at which you define it will depend upon the desired visibility and sharing of the generator. No scoping or visibility rules are actually enforced. Oracle recommends that you define the generator at the level for which it will be used. This generator is based on a database table. | 'Table Sequencing' in the Oracle TopLink Developer's Guide |
Sequence Generator | A primary key generator which you can reference by name, defined at one of the package, class, method, or field level. The level, at which you define it, will depend upon the desired visibility and sharing of the generator. No scoping or visibility rules are actually enforced. Oracle recommends that you define the generator at the level for which it will be used. This generator is based on a sequence object that the database server provides. | 'Native Sequencing With an Oracle Database Platform' in the Oracle TopLink Developer's Guide 'Native Sequencing With a Non-Oracle Database Platform' in the Oracle TopLink Developer's Guide |
Note:
For an EJB 3.0 automatic primary key generation code example, see:http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtoejb30mappingannotations/doc/how-to-ejb30-mapping-annotations.html#sequencing
Using Annotations
Jpa Composite Key Sequence Generator Reviews
Example 7-6 shows how to use the @TableGenerator
annotation to specify a primary key value generator based on a database table. The TopLink JPA persistence provider will attempt to create this table at deployment time: if it cannot, then you must follow your database documentation to ensure that this table exists before deployment. When a new instance of Address
is created, a new value for entity field id
is obtained from ADDRESS_GENERATOR_TABLE
. In this case, you must set the @GeneratedValue
annotation attribute strategy
to TABLE
and generator
to ADDRESS_TABLE_GENERATOR
.
Example 7-6 GeneratedValue Strategy Table: @TableGenerator
Example 7-7 shows how to use the @SequenceGenerator
annotation to specify a primary key value generator based on a sequence object provided by the database. The TopLink JPA persistence provider will attempt to create this object at deployment time: if it cannot, then you must follow your database documentation to ensure that this sequence object exists before deployment. When a new instance of Address
is created, a new value for entity field id
is obtained from database sequence object ADDRESS_SEQ
. In this case, you must set the @GeneratedValue
annotation attribute strategy
to SEQUENCE
and generator
to ADDRESS_SEQUENCE_GENERATOR
.
Sequence Generator Composite Key Jpa
Example 7-7 GeneratedValue Strategy Sequence: @SequenceGenerator
Example 7-8 shows how to use the @GeneratedValue
annotation to specify a primary key value generator based on a primary key identity column (autonumber column). When a new instance of Address
is persisted, the database assigns a value to the identity column. In this case, the TopLink JPA persistence provider re-reads the inserted row and updates the in-memory Address
entity to set id
to this value.
Foreign Key
Jpa Id Generator
1. JPA Composite Key + Sequence stackoverflow.comIs it possible in plain JPA or JPA+Hibernate extensions to declare a composite key, where an element of the composite key is a sequence?This is my composite class:
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2. JPA: InvalidStateException Error + Composite Key/EmbeddableId/Sequence Generated IDs stackoverflow.comI currently have a schema set up with my database and Java Application using OpenJPA that works most of the time, but sometimes I get the error for a few users:org.apache.openjpa.persistence.InvalidStateException: .. |
3. Problem sequence not incremented on annotation composite key forum.hibernate.org@Embeddable public class PrimaryKeyId implements Serializable { /** * */ private static final long serialVersionUID = 2868479904735001761L; @Column(length=2,name='key1') private String nkeyId1='01'; @Column(name='key2') @GeneratedValue(strategy=GenerationType.SEQUENCE,generator='sequenceItem') @SequenceGenerator( name = 'sequenceItem',sequenceName='SEQ_ITEM',allocationSize=1) .. |
4. Multiple sequence definition OR composite id sequence forum.hibernate.orgAuthor Message OldFart Post subject: Multiple sequence definition OR composite id sequence Posted: Mon Apr 18, 2011 10:11 am Beginner Joined: Mon Apr 18, 2011 10:01 am Posts: 20 Hi everybody, I have defined ( I am using Oracle 10 and jdk 1.4 ) a sequence which correctly generates my ID field. I need to populate another two fields .. |
5. Composite-id with sequence forum.hibernate.orgHi all, I'm using hibernate 2.1.1 and Oracle 9.2. I created a mapping for a table with with 3 key-property: 2 strings and an Integer, as a sequence. I read this topic http://forum.hibernate.org/viewtopic.php?t=927648 and i follow your tips, but it still doesn't work. Here is my mapping: |
6. 2 column composite Id, one is a sequence, the other fk forum.hibernate.orgYeah, the sequence is enough, but maybe I didnt made the correct question, I wanted to know if there was a way to tell hibernate to increment sequences using a generator flavor like sequence in its tag, but I used a prepared statement to do that, and I got the connection from hibernate of course.. :-) and used assigned in the .. |
7. parent tbl with sequence and child tbl with composite-key forum.hibernate.orgBeginner Joined: Thu Jul 21, 2005 10:28 am Posts: 21 Need help with Hibernate? Read this first: http://www.hibernate.org/ForumMailingli .. AskForHelp Hibernate version: 3.0.5 Mapping documents: |
9. Using sequence-generated identifier in a composite id. forum.hibernate.orgHi all, I need a helping hand on this one. Consider this mapping, based on these 2 very classic entities : Code: |
10. Using composite ID, one member from various sequences forum.hibernate.orgHere is the setup: I have a table with a two field primary key, I'll call the fields FOO and BAR. BAR is an int that is derived from one of 10 possible Oracle sequences. Which sequence is used is determined by the value of FOO. So if FOO were equal to '001', then we'd call BAR_SEQ_001.nextval. I'm sure you get .. |
12. Add sequence to a composite-id forum.hibernate.orgHello i have a problem. i want add a sequence to a porperty in a composite-id. Something seemed to this: |