四组对象和级联
one-to-many
many-to-one
many-to-many
one-to-one
的四组对象关系，并使用hibernate实现写出
对应的domainobject和对象关系映射文件，并通过hbm2ddl 自动创建成功对应的表
u 级联操作
所谓级联操作就是说，当你进行某个操作(添加/修改/删除...),就由hibernate自动给你完成.
比如: Department <---->Student 对象关系，我希望当我删除一个department ,那么就自动删除该部门的所有学生?
再比如: bbs项目
主帖<---->回帖 , 把主帖删除，那我们就希望把该主帖的回帖自动删除，这样我们可以使用级联(cascade)操作
\
案例:如何配置级联操作，当删除某个部门的时候，我们自动删除其学生.
首先我们在 配置文件中修改:
java代码中操作:
//演示删除级联
//获取到某个部分
Departmentdepartment=(Department) s.get(Department.class, 41);
s.delete(department);
u 演示save-update
配置文件:
代码：
//添加学生
Department department=new Department();
department.setName("业务部门3");
Student stu1=new Student();
stu1.setName("顺平6");
// stu1.setDept(department);
Studentstu2=new Student();
stu2.setName("小明6");
// stu2.setDept(department);
Set
students.add(stu1);
students.add(stu2);
department.setStus(students);
s.save(department);
说明:
①在集合属性和普通属性中都能使用cascade
②一般讲cascade配置在one-to-many(one的一方,比如Employee-Department),和one-to-one(主对象一方)
多对一 对象
student.hbm.xml
stu_seq
dept_seq
package com.hsp.domain;
public class Student implements java.io.Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer id;
private String name;
private Department dept;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Department getDept() {
return dept;
}
public void setDept(Department dept) {
this.dept = dept;
}
}package com.hsp.domain;
public class Department implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer id;
private String name;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
1对1 （主键）
person.hbm.xml
idcard.hbm.xml
person
1对1 (外键)
idcard.hbm.xml
many to many
package com.hsp.domain;
import java.util.Set;
public class Course {
private Integer id;
private String name;
private Set stuCourses;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set getStuCourses() {
return stuCourses;
}
public void setStuCourses(Set stuCourses) {
this.stuCourses = stuCourses;
}
}
package com.hsp.domain;
public class StuCourse {
private Integer id;
private Student student;
private Course course;
private Integer grade;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
public Course getCourse() {
return course;
}
public void setCourse(Course course) {
this.course = course;
}
public Integer getGrade() {
return grade;
}
public void setGrade(Integer grade) {
this.grade = grade;
}
}
package com.hsp.domain;
import java.util.Set;
public class Student {
private Integer id;
private String name;
private Set stuCourses;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set getStuCourses() {
return stuCourses;
}
public void setStuCourses(Set stuCourses) {
this.stuCourses = stuCourses;
}
}
course.hbm.xml
!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
course_seq
StuCourse.hbm.xml
stucourse_seq
Student.hbm.xml
stu_seq
级联
dept_seq
stu_seq