hibernate中的一对多与多对一的配置参考

朱雀 2022-05-20 08:27 109阅读 0赞

1.Employee

1.  package cn.itcast.b\_one2Many;
2.  
3.  public class Employee\{
4.  private int empId;
5.  private String empName;
6.  private double salary;
7.  *//员工与部门（多对一）*
8.  private Dept dept;
9.  public int getEmpId()\{
10. return empId;
11. \}
12. public void setEmpId(int empId)\{
13. this.empId = empId;
14. \}
15. public String getEmpName()\{
16. return empName;
17. \}
18. public void setEmpName(String empName)\{
19. this.empName = empName;
20. \}
21. public double getSalary()\{
22. return salary;
23. \}
24. public void setSalary(double salary)\{
25. this.salary = salary;
26. \}
27. public Dept getDept()\{
28. return dept;
29. \}
30. public void setDept(Dept dept)\{
31. this.dept = dept;
32. \}
33. 
34. 
35. 
36. \}

2.Dept

1.  package cn.itcast.b\_one2Many;
2.  
3.  import java.util.HashSet;
4.  import java.util.Set;
5.  
6.  public class Dept\{
7.  private int deptId;
8.  private String deptName;
9.  *//部门对应的多个员工（一对多）*
10. private Set<Employee> emps= new HashSet<Employee>();
11. public int getDeptId()\{
12. return deptId;
13. \}
14. public void setDeptId(int deptId)\{
15. this.deptId = deptId;
16. \}
17. public String getDeptName()\{
18. return deptName;
19. \}
20. public void setDeptName(String deptName)\{
21. this.deptName = deptName;
22. \}
23. public Set<Employee> getEmps()\{
24. return emps;
25. \}
26. public void setEmps(Set<Employee> emps)\{
27. this.emps = emps;
28. \}
29. 
30. 
31. 
32. \}

3.Employee.hbm.xml

1.  <?xml version="1.0"?>
2.  <!DOCTYPE hibernate-mapping PUBLIC 
3.   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4.   "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
5.  
6.  **
13. **
14. **
17. <hibernate-mapping package="cn.itcast.b\_one2Many">
18. <class name="Employee" table="t\_employee">
19. <id name="empId">
20. <generator class="native"> </generator>
21. </id>
22. <property name="empName" length="20"> </property>
23. <property name="salary" type="double"> </property>
24. 
25. **
30. <many-to-one name="dept" column="dept\_Id" class="Dept"> </many-to-one>
31. 
32. 
33. </class>
34. 
35. 
36. </hibernate-mapping>

4.Dept.hbm.xml

1.  <?xml version="1.0"?>
2.  <!DOCTYPE hibernate-mapping PUBLIC 
3.   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4.   "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
5.  
6.  **
13. **
14. **
17. <hibernate-mapping package="cn.itcast.b\_one2Many">
18. <class name="Dept" table="t\_dept">
19. <id name="deptId">
20. <generator class="native"> </generator>
21. </id>
22. <property name="deptName" length="20"> </property>
23. **
29. <set name="emps" table="t\_employee">
30. <key column="dept\_Id"> </key>
31. <one-to-many class="Employee"> </one-to-many>
32. 
33. </set>
34. 
35. 
36. </class>
37. 
38. 
39. </hibernate-mapping>

5.测试类

1.  package cn.itcast.b\_one2Many;
2.  
3.  
4.  
5.  import org.hibernate.SessionFactory;
6.  import org.hibernate.Transaction;
7.  import org.hibernate.cfg.Configuration;
8.  import org.hibernate.classic.Session;
9.  import org.junit.Test;
10. 
11. public class App\_save\{
12. private static SessionFactory sf;
13. static\{
14. sf= new Configuration()
15. .configure()
16. .addClass(Dept.class)
17. .addClass(Employee.class) *//测试的时候使用*
18. .buildSessionFactory();
19. \}
20. 
21. *//保存，通过部门方保存数据（一对多操作保存数据）*
22. @Test
23. public void Save()\{
24. Session session=sf.openSession();
25. session.beginTransaction();
26. *//部门对象*
27. Dept dept= new Dept();
28. dept.setDeptName( "应用开发部");
29. *//员工对象*
30. Employee emp\_zs= new Employee();
31. emp\_zs.setEmpName( "张三");
32. Employee emp\_ls= new Employee();
33. emp\_ls.setEmpName( "李四");
34. *//处理关系*
35. dept.getEmps().add(emp\_zs);
36. dept.getEmps().add(emp\_ls);
37. 
38. *//保存数据*
39. session.save(emp\_zs);
40. session.save(emp\_ls);
41. session.save(dept);
42. 
43. session.getTransaction().commit();
44. session.close();
45. 
46. */\* Hibernate: insert into t\_employee (empName, salary, dept\_Id) values (?, ?, ?)*
47.  *Hibernate: insert into t\_employee (empName, salary, dept\_Id) values (?, ?, ?)*
48.  *Hibernate: insert into t\_dept (deptName) values (?)*
49.  *Hibernate: update t\_employee set dept\_Id=? where empId=? //维护员工部门引用的id*
50.  *Hibernate: update t\_employee set dept\_Id=? where empId=?*
51. *\*/*
52. 
53. 
54. \}
55. *//推荐：用多的一方来保存数据，减少数据库维护的次数*
56. *//保存数据，通过员工方保存数据（多对一操作数据）*
57. @Test
58. public void Save2()\{
59. Session session=sf.openSession();
60. session.beginTransaction();
61. *//部门对象*
62. Dept dept= new Dept();
63. dept.setDeptName( "人事部");
64. *//员工对象*
65. Employee emp\_zs= new Employee();
66. emp\_zs.setEmpName( "张三");
67. Employee emp\_ls= new Employee();
68. emp\_ls.setEmpName( "李四");
69. *//处理关系*
70. emp\_zs.setDept(dept);
71. emp\_ls.setDept(dept);
72. *//保存数据*
73. *//先保存一的一方，再保存多的一方，这样关系会自动维护（配置映射一定要正确）*
74. session.save(dept); *//保存部门下的所有员工*
75. session.save(emp\_zs);
76. session.save(emp\_ls);
77. 
78. 
79. session.getTransaction().commit();
80. session.close();
81. 
82. */\* Hibernate: insert into t\_dept (deptName) values (?)*
83.  *Hibernate: insert into t\_employee (empName, salary, dept\_Id) values (?, ?, ?)*
84.  *Hibernate: insert into t\_employee (empName, salary, dept\_Id) values (?, ?, ?)*
85.  *少生成2条update的sql*
86. *\*/*
87. 
88. 
89. \}
90. \}

6.hibernate.cfg.xml

1.  <!DOCTYPE hibernate-configuration PUBLIC
2.   "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
3.   "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
4.  
5.  <hibernate-configuration>
6.  **
7.  <session-factory>
8.  **
9.  <property name="hibernate.connection.driver\_class">com.mysql.jdbc.Driver </property>
10. <property name="hibernate.connection.url">jdbc:mysql:///hib-demo </property>
11. <property name="hibernate.connection.username">root </property>
12. <property name="hibernate.connection.password">123456 </property>
13. **
14. <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect </property>
15. 
16. **
17. **
18. <property name="hibernate.show\_sql">true </property>
19. **
21. **
22. <property name="hibernate.hbm2ddl.auto">update </property>
23. **
25. </session-factory>
26. </hibernate-configuration>
27.