Hibernate Generate Uuid As Primary Keys
17.12.2020 admin
Jul 04, 2019 Some of its usage are for creating random file names, session id in web application, transaction id and for record’s primary keys in database replacing the sequence or auto generated number. To generate UUID in Java we can use the java.util.UUID class. Oct 28, 2018 Note that for both types of composite ids, the primary key class can also contain @ManyToOne attributes. Hibernate also allows defining primary-keys made up of @ManyToOne associations combined with @Id annotation. In this case, the entity class should also fulfill the conditions of a primary-key class. Feb 28, 2016 Auto increment keys vs. Tldr: Programmers should love values and UUID is a value. Today I would like to write about not so obvious point of view on. Most developers prefer numerical primary keys because they are efficient to use and easy to generate. But that doesn’t mean that a primary key has to be a number. UUIDs, for example, have gained some popularity over the recent years.
UniqueId (UUID) embedded primary key in JPA 2 (Hibernate) for MySQL
UniqueId.java
| importjava.io.Serializable; |
| importjava.nio.ByteBuffer; |
| importjava.util.Arrays; |
| importjava.util.UUID; |
| importjavax.persistence.Access; |
| importjavax.persistence.AccessType; |
| importjavax.persistence.Column; |
| importjavax.persistence.Embeddable; |
| @Embeddable |
| @Access(AccessType.FIELD) |
| publicclassUniqueIdimplementsSerializable { |
| privatestaticfinallong serialVersionUID =4458438725376203754L; |
| @Column(columnDefinition='BINARY(16)', length=16, updatable=false, nullable=false) |
| privatebyte[] id; |
| publicUniqueId() {} |
| publicUniqueId(byte[] id) { |
| this.id = id; |
| } |
| publicUniqueId(Stringid) { |
| this(toByteArray(UUID.fromString(id))); |
| } |
| @Override |
| publicStringtoString() { |
| return toUUID(id).toString(); |
| } |
| publicstaticUniqueIdfromString(Strings) { |
| return fromUUID(UUID.fromString(s)); |
| } |
| publicstaticUniqueIdfromUUID(UUIDuuid) { |
| returnnewUniqueId(toByteArray(uuid)); |
| } |
| privatestaticbyte[] toByteArray(UUIDuuid) { |
| ByteBuffer bb =ByteBuffer.wrap(newbyte[16]); |
| bb.putLong(uuid.getMostSignificantBits()); // order is important here! |
| bb.putLong(uuid.getLeastSignificantBits()); |
| return bb.array(); |
| } |
| privatestaticUUIDtoUUID(byte[] byteArray) { |
| long msb =0; |
| long lsb =0; |
| for (int i =0; i <8; i++) |
| msb = (msb <<8) (byteArray[i] &0xff); |
| for (int i =8; i <16; i++) |
| lsb = (lsb <<8) (byteArray[i] &0xff); |
| UUID result =newUUID(msb, lsb); |
| return result; |
| } |
| @Override |
| publicinthashCode() { |
| finalint prime =31; |
| int result =1; |
| result = prime * result +Arrays.hashCode(id); |
| return result; |
| } |
| @Override |
| publicbooleanequals(Objectobj) { |
| if (this obj) |
| returntrue; |
| if (obj null) |
| returnfalse; |
| if (getClass() != obj.getClass()) |
| returnfalse; |
| UniqueId other = (UniqueId) obj; |
| if (!Arrays.equals(id, other.id)) |
| returnfalse; |
| returntrue; |
| } |
| publicstaticUniqueIdgenerate() { |
| return fromUUID(UUID.randomUUID()); |
| } |
| } |
Hibernate Generate Uuid As Primary Keys Free
commented Feb 12, 2016
Hibernate Generate Uuid As Primary Keys List
Lifesaver! Used this for general byte[] primary keys with a reordered UUID component |
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Most developers prefer numerical primary keys because they are efficient to use and easy to generate. But that doesn’t mean that a primary key has to be a number. UUIDs, for example, have gained some popularity over the recent years. The main advantage of a UUID is its (practical) global uniqueness which provides a huge advantage for distributed systems. If you use the typical, numerical ID that gets incremented for each new record, you need to generate all IDs by the same component of your system or the components need to communicate with each other. /key-generation-bar-key-not-moving.html. With a globally unique UUID, you don’t need all of this. Each component can generate a UUID and there will not be any conflicts.