自定义主键生成策略,由@GenericGenerator实现。
hibernate在JPA的基础上进行了扩展,可以用一下方式引入hibernate独有的主键生成策略,就是通过@GenericGenerator 加入的。
比如说,JPA标准用法
Java代码
1. @Id
2. @GeneratedValue(GenerationType.AUTO)
就可以用hibernate特有以下用法来实现
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "assigned")
@GenericGenerator的定义:
Java代码
1. @Target({PACKAGE, TYPE, METHOD, FIELD})
2. @Retention(RUNTIME)
3. public @interface GenericGenerator {
4.
5. String name();
6.
7. String strategy();
8.
9. Parameter[] parameters() default {};
10. }
name属性指定生成器名称。
strategy属性指定具体生成器的类名。
parameters得到strategy指定的具体生成器所用到的参数。
对于这些hibernate主键生成策略和各自的具体生成器之间的关系,在 org.hibernate.id.IdentifierGeneratorFactory中指定了,
Java代码
1. static {
2. GENERATORS.put("uuid", UUIDHexGenerator.class);
3. GENERATORS.put("hilo", TableHiLoGenerator.class);
4. GENERATORS.put("assigned", Assigned.class);
5. GENERATORS.put("identity", IdentityGenerator.class);
6. GENERATORS.put("select", SelectGenerator.class);
7. GENERATORS.put("sequence", SequenceGenerator.class);
8. GENERATORS.put("seqhilo", SequenceHiLoGenerator.class);
9. GENERATORS.put("increment", IncrementGenerator.class);
10. GENERATORS.put("foreign", ForeignGenerator.class);
11. GENERATORS.put("guid", GUIDGenerator.class);
12. GENERATORS.put("uuid.hex", UUIDHexGenerator.class); //uuid.hex is deprecated
13. GENERATORS.put("sequence-identity", SequenceIdentityGenerator.class);
14. }
上面十二种策略,加上native,hibernate一共默认支持十三种生成策略。
1、native
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "native")
2、uuid
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "uuid")
3、hilo
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "hilo")
4、assigned
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "assigned")
5、identity
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "identity")
6、select
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name="select", strategy="select",
3. parameters = { @Parameter(name = "key", value = "idstoerung") })
7、sequence
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "sequence",
3. parameters = { @Parameter(name = "sequence", value = "seq_payablemoney") })
8、seqhilo
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "seqhilo",
3. parameters = { @Parameter(name = "max_lo", value = "5") })
9、increment
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "increment")
10、foreign
Java代码
1. @GeneratedValue(generator = "idGenerator")
2. @GenericGenerator(name = "idGenerator", strategy = "foreign",
3. parameters = { @Parameter(name = "property", value = "employee") })
注意:直接使用@PrimaryKeyJoinColumn 报错(?)
Java代码
1. @OneToOne(cascade = CascadeType.ALL)
2. @PrimaryKeyJoinColumn
例如
Java代码
1. @Entity
2. public class Employee {
3. @Id Integer id;
4.
5. @OneToOne @PrimaryKeyJoinColumn
6. EmployeeInfo info;
7. ...
8. }
应该为
Java代码
1. @Entity
2. public class Employee {
3. @Id
4. @GeneratedValue(generator = "idGenerator")
5. @GenericGenerator(name = "idGenerator", strategy = "foreign",
6. parameters = { @Parameter(name = "property", value = "info") })
7. Integer id;
8.
9. @OneToOne
10. EmployeeInfo info;
11. ...
12. }
11、guid
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "guid")
12、uuid.hex
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "uuid.hex")
13、sequence-identity
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "sequence-identity",
3. parameters = { @Parameter(name = "sequence", value = "seq_payablemoney") })
四、通过@GenericGenerator自定义主键生成策略
如果实际应用中,主键策略为程序指定了就用程序指定的主键(assigned),没有指定就从sequence中取。
明显上面所讨论的策略都不满足,只好自己扩展了,集成assigned和sequence两种策略。
Java代码
1. public class AssignedSequenceGenerator extends SequenceGenerator implements
2. PersistentIdentifierGenerator, Configurable {
3. private String entityName;
4.
5. public void configure(Type type, Properties params, Dialect dialect) throws MappingException {
6. entityName = params.getProperty(ENTITY_NAME);
7. if (entityName==null) {
8. throw new MappingException("no entity name");
9. }
10.
11. super.configure(type, params, dialect);
12. }
13.
14. public Serializable generate(SessionImplementor session, Object obj)
15. throws HibernateException {
16.
17. Serializable id = session.getEntityPersister( entityName, obj )
18. .getIdentifier( obj, session.getEntityMode() );
19.
20. if (id==null) {
21. id = super.generate(session, obj);
22. }
23.
24. return id;
25. }
26. }
实际应用中,定义同sequence。
Java代码
1. @GeneratedValue(generator = "paymentableGenerator")
2. @GenericGenerator(name = "paymentableGenerator", strategy = "AssignedSequenceGenerator",
3. parameters = { @Parameter(name = "sequence", value = "seq_payablemoney") })