Hibernate 關聯映射 - gcs1995－IT工程師數位筆記本

文章出處

實體之間的關系
　　關聯，聚合，依賴，組合，繼承

關系的類型：
　　一對多
　　多對一
　　一對一
　　多對多

　　學生表和年級表：

 1 --學生表
 2 create table student(
 3        stuno number(4) primary key,
 4        name varchar2(20) not null,
 5        gradeid number(4)
 6 
 7 )
 8 --年級表
 9 create table grade(
10        gradeid number(4) primary key,
11        gradename varchar2(20) not null
12 
13 )

當一對多和多對一關系組合就是雙向關聯了

　　所以整合在一起寫了個添加數據和刪除外鍵表的級聯代碼

　　1.建立對象

　　　　student:　　　　

 1 package entity;
 2 
 3 import java.io.Serializable;
 4 /**
 5  * 學生實體類
 6  * @author Administrator
 7  *
 8  */
 9 public class Student implements Serializable{
10     private Integer stuno;
11     private String name;
12     private Integer gradeid;
13     //學生與年級屬于多多對一的關系
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  * 年級實體類
 7  * @author Administrator
 8  *
 9  */
10 public class Grade implements Serializable{
11     //年級編號
12     private Integer gradeid;
13     //年級
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.建立對象之間的關系

 1 <!--grade表-->
 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 <hibernate-mapping
 8     package="entity">
 9     
10     <class name="Grade" table="grade" dynamic-update="true">
11         <id name="gradeid" type="integer">
12             <generator class="assigned">
13                 
14             </generator>
15         </id>
16         <property name="gradename" type="java.lang.String" />
17         <set name="stu" cascade="all">
18             <key column="gradeid"/>
19             <one-to-many class="Student"/>
20         </set>
21         
22     </class>
23 </hibernate-mapping>
24 
25 
26 <!--student表-->
27 <?xml version="1.0"?>
28 <!DOCTYPE hibernate-mapping PUBLIC 
29     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
30     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
31 
32 <hibernate-mapping
33     package="entity">
34     
35     <class name="Student" table="student" dynamic-update="true">
36         <id name="stuno" type="integer">
37             <generator class="sequence">
38                 <param name="sequence">seq_student</param>
39             </generator>
40         </id>
41         <property name="name" type="java.lang.String" />
42         
43         <!-- 多對一關系 -->
44         <many-to-one name="grade" class="Grade">
45             <column name="gradeid"></column>
46         </many-to-one>
47     </class>
48 </hibernate-mapping>

兩表的配置文件

　　3.配置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 <hibernate-configuration>
 6     <session-factory>
 7         
 8         <!-- 指定oracle對應得dialect -->
 9         <property name="dialect">
10             org.hibernate.dialect.Oracle10gDialect
11         </property>
12         <!-- 數據庫jdbc驅動 -->
13         <property name="connection.driver_class">
14             oracle.jdbc.driver.OracleDriver
15         </property>
16         
17         <!-- 數據庫url -->
18         <property name="connection.url">
19             jdbc:oracle:thin:@localhost:1521:XE
20         </property>
21         
22         <!-- 用戶名 -->
23         <property name="connection.username">super_user</property>
24         <!-- 用戶密碼 -->
25         <property name="connection.password">abc123</property>
26         
27         <!-- session范圍和上下文 -->
28         <property name="current_session_context_class">thread</property>
29         <!-- 是否在運行期間生成的SQL輸出到日志以供調試 -->
30         <property name="show_sql">true</property>
31         <!-- 是否格式化sql -->
32         <property name="format_sql">true</property>
33         <!-- 根據映射文件自動生成表-->
34         <property name="hbm2ddl.auto">update</property> 
35         <!-- 映射 -->
36         <mapping resource="entity/Grade.hbm.xml" />
37         <mapping resource="entity/Student.hbm.xml" />
38         
39     </session-factory>
40 </hibernate-configuration>

　　上面配置文件中出現了三個新的配置節點，和新的節點屬性：

　　　1.<set name="stu" cascade="all"> --name指定對象中屬性名 cascade：級聯 ————》all/none/save-update/delete/都是字面意思

　　　　<key column="gradeid"/>　　　　--指定兩個對象關聯的主鍵
　　　　<one-to-many class="Student"/>　　--這里是個一對多關系的實體類配置，因為我在mapping中配置了package所以這里只寫類名
　　　</set>

　　　2.<many-to-one name="grade" class="Grade"> --指定對象中處于“一”關系的屬性名，并且指明類名

　　　　<column name="gradeid"></column>　　　　--制定關聯的主鍵
　　　　</many-to-one>

　　　3.<property name="hbm2ddl.auto">update</property> --指定操作類型

　　　　　　#hibernate.hbm2ddl.auto create-drop
　　　　　　#hibernate.hbm2ddl.auto create
　　　　　　#hibernate.hbm2ddl.auto update
　　　　　　#hibernate.hbm2ddl.auto validate

　　測試代碼：

 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  * 多對一關系聯動練習
13  * @author Administrator
14  *
15  */
16 public class StudentDao {
17     //打開配置
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 block
28             e.printStackTrace();
29             
30         }
31     }
32     /**
33      * 新增
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("一年級");
44         session.save(grade);
45         student.setName("小明");
46         student.setGrade(grade);
47         session.save(student);
48         session.getTransaction().commit();
49         System.out.println("成功！");
50         
51         session.close();
52     }
53     /**
54      * 刪除
55      */
56     public void del(){
57         session=factory.openSession();
58         session.beginTransaction();
59         //Student student=(Student)session.get(Student.class, 5);
60         //級聯刪除
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("成功！");
66         
67         session.close();
68     }
69 }