Combined primary key generation policy in Hibernate, hibernate primary key

Combined primary key generation policy in Hibernate, hibernate primary key
I. Configure the joint primary key in xml

Design a class separately as the primary key class, such as StudentPK

A. Serializable Interface)

B. Rewrite equals () and hashCode ()

Why do I need to write equals () and hashCode () methods?

The same hashCode is stored in the same location of the hash table. After a specific hashcode is found, the corresponding data is searched based on the equals () method.

Lab 1:

(1) create a joint primary key class StudentPK

Package com. zgy. hibernate. model;

 

Import java. io. Serializable;

 

Public class StudentPK implements Serializable {

Private int id;

Private String name;

Public int getId (){

Return id;

}

Public void setId (int id ){

This. id = id;

}

Public String getName (){

Return name;

}

Public void setName (String name ){

This. name = name;

}

Public boolean equals (Object o ){

If (o instanceof StudentPK ){

StudentPK = (StudentPK) o;

If (this. id = pk. getId () & this. name = pk. getName ()){

Return true;

}

}

Return false;

}

Public int hashCode (){

Return this. name. hashCode ();

}

}

 

(2) configure the joint primary key using xml

<? Xml version = "1.0"?>

<! DOCTYPE hibernate-mapping PUBLIC

"-// Hibernate/Hibernate Mapping DTD 3.0 // EN"

Http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd>

 

<Hibernate-mapping package = "com. zgy. hibernate. model">

<Class name = "Student" table = "student">

<! -- <Id name = "id" column = "id">

<Generator class = "native"> </generator>

</Id>

<Property name = "name" column = "name"> </property>

-->

 

<! -- Configure the Union primary key -->

<Composite-id name = "pk" class = "com. zgy. hibernate. model. StudentPK">

<Key-property name = "id"> </key-property>

<Key-property name = "name"> </key-property>

</Composite-id>

<Property name = "age" column = "age"> </property>

<Property name = "score" column = "score"> </property>

</Class>

</Hibernate-mapping>

(3) Compile the test program

Package com. zgy. hibernate. model;

 

Import static org. junit. Assert .*;

 

Import java. util. Date;

 

Import org. hibernate. Session;

Import org. hibernate. SessionFactory;

Import org. hibernate. cfg. AnnotationConfiguration;

Import org. junit. AfterClass;

Import org. junit. BeforeClass;

Import org. junit. Test;

 

Public class HibernateIDTest {

 

Public static SessionFactory sf = null;

@ BeforeClass

Public static void beforeClass (){

Sf = new AnnotationConfiguration (). configure (). buildSessionFactory ();

}

@ Test

Public void testStudent (){

 

StudentPK = new StudentPK ();

Pk. setId (1 );

Pk. setName ("zhangsan ");

Student s = new Student ();

S. setPk (pk );

// S. setName ("James ");

S. setAge (20 );

S. setScore (90 );

Session session = sf. openSession ();

Session. beginTransaction ();

Session. save (s );

Session. getTransaction (). commit ();

Session. close ();

}

 

@ AfterClass

Public static void afterClass (){

Sf. close ();

}

 

}

 

2. Annotation Method 1: Use @ Embeddable

Configure @ Embeddable on the Union primary key class

In Teacher. java, write @ Id on getPk ()

Lab 2:

(1) Create TeacherPK. java

Package com. zgy. hibernate. model;

 

Import java. io. Serializable;

 

Import javax. persistence. Embeddable;

@ Embeddable

Public class TeacherPK implements Serializable {

Private int id;

Private String name;

Public int getId (){

Return id;

}

Public void setId (int id ){

This. id = id;

}

Public String getName (){

Return name;

}

Public void setName (String name ){

This. name = name;

}

Public boolean equals (Object o ){

If (o instanceof TeacherPK ){

TeacherPK pk = (TeacherPK) o;

If (this. id = pk. getId () & this. name = pk. getName ()){

Return true;

}

}

Return false;

}

Public int hashCode (){

Return this. name. hashCode ();

}

}

 

(2) test

Package com. zgy. hibernate. model;

 

Import static org. junit. Assert .*;

 

Import java. util. Date;

 

Import org. hibernate. Session;

Import org. hibernate. SessionFactory;

Import org. hibernate. cfg. AnnotationConfiguration;

Import org. hibernate. cfg. Configuration;

Import org. junit. AfterClass;

Import org. junit. BeforeClass;

Import org. junit. Test;

 

Public class TeacherTesting {

Public static SessionFactory sf = null;

@ BeforeClass

Public static void beforeClass (){

Sf = new AnnotationConfiguration (). configure (). buildSessionFactory ();

}

@ Test

Public void test (){

TeacherPK pk = new TeacherPK ();

Pk. setId (1 );

Pk. setName ("t1 ");

Teacher t = new Teacher ();

T. setPk (pk );

// T. setName ("t1 ");

T. setTitle ("advanced ");

T. setAddress ("Beijing ");

T. setBirth (new Date ());

T. setZhiCheng (ZhiCheng. );

Session session = sf. openSession ();

Session. beginTransaction ();

Session. save (t );

Session. getTransaction (). commit ();

Session. close ();

}

 

@ AfterClass

Public static void afterClass (){

Sf. close ();

}

}

 

(3) view results

 

Select * from teacher;

Desc teacher;

 

 

 

Method 2: Add @ EmbeddedId TO THE METHOD

Add @ EmbeddedId directly to the getPK () method in Teacher. java.

Lab 3:

(1) Modify Teacher. java

Package com. zgy. hibernate. model;

 

Import java. util. Date;

 

Import javax. annotation. Generated;

Import javax. persistence. Column;

Import javax. persistence. EmbeddedId;

Import javax. persistence. Entity;

Import javax. persistence. EnumType;

Import javax. persistence. Enumerated;

Import javax. persistence. GeneratedValue;

Import javax. persistence. GenerationType;

Import javax. persistence. Id;

Import javax. persistence. Table;

Import javax. persistence. Temporal;

Import javax. persistence. TemporalType;

Import javax. persistence. Transient;

 

@ Entity

@ Javax. persistence. TableGenerator (

Name = "Teacher_GEN ",

Table = "GENERATOR_TABLE ",

PkColumnName = "pkkey ",

ValueColumnName = "pkvalue ",

PkColumnValue = "Teacher ",

AllocationSize = 1

)

Public class Teacher {

// Private int id;

// Private String name;

Private String title;

Private String address;

Private String wifeName;

Private Date birth;

Private ZhiCheng zhiCheng;

@ Id

@ GeneratedValue (strategy = GenerationType. TABLE, generator = "Teacher_GEN ")

// Public int getId (){

// Return id;

//}

// Public void setId (int id ){

// This. id = id;

//}

// @ Column (name = "_ name ")

// Public String getName (){

// Return name;

//}

// Public void setName (String name ){

// This. name = name;

//}

Private TeacherPK;

Public String getTitle (){

Return title;

}

Public void setTitle (String title ){

This. title = title;

}

Public String getAddress (){

Return address;

}

Public void setAddress (String address ){

This. address = address;

}

 

Public String getWifeName (){

Return wifeName;

}

Public void setWifeName (String wifeName ){

This. wifeName = wifeName;

}

@ Temporal (TemporalType. DATE)

Public Date getBirth (){

Return birth;

}

Public void setBirth (Date birth ){

This. birth = birth;

}

@ Enumerated (EnumType. STRING)

Public ZhiCheng getZhiCheng (){

Return zhiCheng;

}

Public void setZhiCheng (ZhiCheng zhiCheng ){

This. zhiCheng = zhiCheng;

}

@ EmbeddedId

Public TeacherPK getPk (){

Return pk;

}

Public void setPk (TeacherPK pk ){

This. pk = pk;

}

 

}

 

(2) test

(3) view results

 

Select * from teacher;

Desc teacher;

 

 

 

Method 3:

(1) Modify in Teacher. java, add @ Id on getId (), getName (), and add @ IdClass (value = TeacherPK. class) on the Teacher class Name)

Package com. zgy. hibernate. model;

 

Import java. util. Date;

 

Import javax. annotation. Generated;

Import javax. persistence. Column;

Import javax. persistence. EmbeddedId;

Import javax. persistence. Entity;

Import javax. persistence. EnumType;

Import javax. persistence. Enumerated;

Import javax. persistence. GeneratedValue;

Import javax. persistence. GenerationType;

Import javax. persistence. Id;

Import javax. persistence. IdClass;

Import javax. persistence. Table;

Import javax. persistence. Temporal;

Import javax. persistence. TemporalType;

Import javax. persistence. Transient;

 

@ Entity

@ Javax. persistence. TableGenerator (

Name = "Teacher_GEN ",

Table = "GENERATOR_TABLE ",

PkColumnName = "pkkey ",

ValueColumnName = "pkvalue ",

PkColumnValue = "Teacher ",

AllocationSize = 1

)

@ IdClass (value = TeacherPK. class)

Public class Teacher {

Private int id;

Private String name;

Private String title;

Private String address;

Private String wifeName;

Private Date birth;

Private ZhiCheng zhiCheng;

@ Id

// @ GeneratedValue (strategy = GenerationType. TABLE, generator = "Teacher_GEN ")

Public int getId (){

Return id;

}

Public void setId (int id ){

This. id = id;

}

@ Column (name = "_ name ")

@ Id

Public String getName (){

Return name;

}

Public void setName (String name ){

This. name = name;

}

Private TeacherPK;

Public String getTitle (){

Return title;

}

Public void setTitle (String title ){

This. title = title;

}

Public String getAddress (){

Return address;

}

Public void setAddress (String address ){

This. address = address;

}

 

Public String getWifeName (){

Return wifeName;

}

Public void setWifeName (String wifeName ){

This. wifeName = wifeName;

}

@ Temporal (TemporalType. DATE)

Public Date getBirth (){

Return birth;

}

Public void setBirth (Date birth ){

This. birth = birth;

}

@ Enumerated (EnumType. STRING)

Public ZhiCheng getZhiCheng (){

Return zhiCheng;

}

Public void setZhiCheng (ZhiCheng zhiCheng ){

This. zhiCheng = zhiCheng;

}

/*

@ EmbeddedId

Public TeacherPK getPk (){

Return pk;

}

Public void setPk (TeacherPK pk ){

This. pk = pk;

}

*/

}

 

(2) test

(3) view results

 

Select * from teacher;

Desc teacher;