Hibernate Association ing and hibernate Association ing

Hibernate Association ing and hibernate Association ing

Relationship between entities
Association, aggregation, dependency, combination, inheritance

Link Type:
One-to-multiple
Many-to-one
One-to-one
Many-to-many

 

Student table and grade Table:

1 -- student table 2 create table student (3 stuno number (4) primary key, 4 name varchar2 (20) not null, 5 gradeid number (4) 6 7) 8 -- grade table 9 create table grade (10 gradeid number (4) primary key, 11 gradename varchar2 (20) not null12 13)

 

A one-to-many and one-to-one relationship combination is a bidirectional Association.

Therefore, the integration writes a cascade code for adding data and deleting foreign key tables.

1. Create an object

Student:

1 package entity; 2 3 import java. io. serializable; 4/** 5 * Student Entity class 6 * @ author Administrator 7*8 */9 public class Student implements Serializable {10 private Integer stuno; 11 private String name; 12 private Integer gradeid; 13 // The relationship between students and grades is many-to-one. 14 private Grade grade; 15 16 public Student () {} 17 public Integer getStuno () {18 return stuno; 19} 20 public void setStuno (Integer stuno) {21 this. stuno = stuno; 22} 23 public String getName () {24 return name; 25} 26 public void setName (String name) {27 this. name = name; 28} 29 public Integer getGradeid () {30 return gradeid; 31} 32 public void setGradeid (Integer gradeid) {33 this. gradeid = gradeid; 34} 35 public Grade getGrade () {36 return grade; 37} 38 public void setGrade (Grade grade) {39 this. grade = grade; 40} 41 42 43}Student

Grade:

1 package entity; 2 3 import java. io. serializable; 4 import java. util. set; 5/** 6 * Grade entity class 7 * @ author Administrator 8*9 */10 public class Grade implements Serializable {11 // Grade number 12 private Integer gradeid; 13 // Grade 14 private String gradename; 15 16 private Set <Student> stu; 17 18 public Grade () {} 19 20 public Set <Student> getStu () {21 return stu; 22} 23 24 public void setStu (Set <Student> stu) {25 this. stu = stu; 26} 27 28 public Integer getGradeid () {29 return gradeid; 30} 31 public void setGradeid (Integer gradeid) {32 this. gradeid = gradeid; 33} 34 public String getGradename () {35 return gradename; 36} 37 public void setGradename (String gradename) {38 this. gradename = gradename; 39} 40 41 42 43}Grade

 

2. Establish the relationship between objects

1 <! -- Grade Table --> 2 <? Xml version = "1.0"?> 3 <! DOCTYPE hibernate-mapping PUBLIC 4 "-// Hibernate/Hibernate Mapping DTD 3.0 // EN" 5" http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd "> 6 7 3. Configure hibernate

1 <! DOCTYPE hibernate-configuration PUBLIC 2 "-// Hibernate/Hibernate Configuration DTD 3.0 // EN" 3" http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd "> 4 5 
The preceding configuration file contains three new configuration nodes and new node attributes:
1. <set name = "stu" cascade = "all"> -- name specifies the attribute name in the object. cascade: cascade ---- all/none/save-update/delete/is literal.
<Key column = "gradeid"/> -- specifies the primary key associated with two objects.
<One-to-learn class = "Student"/> -- this is a one-to-many object class configuration. Because I have configured package in mapping, only the class name is written here.
</Set>
2.<Role-to-one name = "grade" class = "Grade"> -- specifies the attribute name of the object in the "1" link and specifies the class name.
<Column name = "gradeid"> </column> -- specify the associated primary key.
</Role-to-one>
 
3. <property name = "hbm2ddl. auto"> update </property> -- specify the operation type.
# Hibernate. hbm2ddl. auto create-drop
# Hibernate. hbm2ddl. auto create
# Hibernate. hbm2ddl. auto update
# Hibernate. hbm2ddl. auto validate
　　
Test code:
　　　　
1 package dao; 2 3 import org. hibernate. session; 4 import org. hibernate. sessionFactory; 5 import org. hibernate. transaction; 6 import org. hibernate. cfg. configuration; 7 8 import entity. grade; 9 import entity. student; 10 11/** 12 * multi-to-one link linkage exercise 13 * @ author Administrator14 * 15 */16 public class StudentDao {17 // open the Configuration 18 SessionFactory factory = new Configuration (). configure (). buildSessionFactory (); 19 Session Session = null; 20 21 public static void main (String [] args) {22 StudentDao stu = new StudentDao (); 23 try {24 // stu. update (); 25 stu. del (); 26} catch (Exception e) {27 // TODO Auto-generated catch block28 e. printStackTrace (); 29 30} 31} 32/** 33 * added 34 */35 public void update () throws Exception {36 session = factory. openSession (); 37 session. beginTransaction (); 38 // Grade grade = (Grade) session. get (Grade. class, 1); 39 40 Student student = new Student (); 41 Grade grade = new Grade (); 42 grade. setGradeid (1); 43 grade. setGradename ("First Grade"); 44 session. save (grade); 45 student. setName ("James"); 46 student. setGrade (grade); 47 session. save (student); 48 session. getTransaction (). commit (); 49 System. out. println ("successful! "); 50 51 session. close (); 52} 53/** 54 * Delete 55 */56 public void del () {57 session = factory. openSession (); 58 session. beginTransaction (); 59 // Student student = (Student) session. get (Student. class, 5); 60 // cascade Delete 61 Grade grade = (Grade) session. get (Grade. class, 1); 62 session. delete (grade); 63 // session. delete (student); 64 session. getTransaction (). commit (); 65 System. out. println ("successful! "); 66 67 session. close (); 68} 69}



 
 
Problems encountered in code: http://www.cnblogs.com/gcs1995/p/4139422.html