Hibernate双向多对多实现 [英] Hibernate Bidirectional Many to Many implementation

问题描述

我是hibernate的新手，我想在hibernate中实现这样的东西。为了能够这样做，我在设置xml映射文件时遇到问题。如果有人可以帮助我，这将是非常好的，因为这只是概念的证明我想做，我有很多复杂的事情要做。谢谢

  public class课程实现java.io.Serializable 
 {
 private long courseId; 
 private String courseName; 
 private Set< Student> Stu = new HashSet< Student>（）; 
} 
 
 public class Student implements java.io.Serializable 
 {
 
 private long studentId; 
 private String studentName; 
 private Set< Course> courses = new HashSet< Course>（）; 
} 
  

但在数据库中，我想要创建3个表
学生，课程和学生课程

 学生-----> studentCourse <------课程
 StudentId StudentId CourseId 
 CourseId 
  

我想要的是，当我做

 课程C1 =（课程）session.get（Course.class，CourseId）
  

我得到指定的课程，并通过

  Set< Student> ; StudentsEnrolled = C1.getStu（）; 
  

我获得所有参加该课程的学生

Similary
当我做

 学生S1 =（学生）session.get（Student.class，StudentId） 
  

我得到指定的学生，并通过

 设置< Course> CoursesEnrolled = S1.getCourses（）; 
  

我获得指定学生参加的所有课程

解决方案

查看 this

 < hibernate-mapping> 
< class name =com.vaannila.student.Studenttable =STUDENT> 
< meta attribute =class-description>此类包含学生详细信息。< / meta> 
< id name =studentIdtype =longcolumn =STUDENT_ID> 
< generator class =native/> 
< / id> 
< property name =studentNametype =stringlength =100not-null =truecolumn =STUDENT_NAME/> 
< set name =coursestable =STUDENT_COURSEcascade =all> 
< key column =STUDENT_ID/> 
< many-to-many column =COURSE_IDclass =com.vaannila.student.Course/> 
< / set> 
< / class> 
< / hibernate-mapping> 
 
< hibernate-mapping> 
< class name =com.vaannila.student.Coursetable =COURSE> 
< meta attribute =class-description>此课程包含课程详情。< / meta> 
< id name =courseIdtype =longcolumn =COURSE_ID> 
< generator class =native/> 
< / id> 
< property name =courseNametype =stringcolumn =COURSE_NAME/> 
< set name =studentstable =STUDENT_COURSEcascade =all> 
< key column =COURSE_ID/> 
< many-to-many column =STUDENT_IDclass =com.vaannila.student.Student/> 
< / set> 
< / class> 
< / hibernate-mapping> 
  

好吧，如果你镜像在其他类这样的集合不工作？ >

I am new to hibernate and I want to implement something like this in hibernate. To be able to do this, I am getting problem in setting the xml mapping file. If someone can help me, it would be very nice as this is just of proof of concept I am trying to do, I have much complicated things to do.Thanks

public class Course implements java.io.Serializable 
{
    private long courseId;
    private String courseName;
    private Set <Student> Stu = new HashSet <Student>();
}

public class Student implements java.io.Serializable 
{

    private long studentId;
    private String studentName;
    private Set<Course> courses = new HashSet<Course>();
}

But in the database, I want 3 table to be created Student,Course and StudentCourse

              Student----->StudentCourse<------Course 
            StudentId      StudentId          CourseId     
                            CourseId     

What I want is that when I do

 Course C1=(Course)session.get(Course.class,CourseId)

I get the specified course and by doing

  Set <Student> StudentsEnrolled=C1.getStu();

I get all students enrolled in that course

Similary When I do

Student S1=(Student)session.get(Student.class,StudentId)

I get the specified student and by doing

Set <Course> CoursesEnrolled=S1.getCourses();

I get all courses the specified student has taken

解决方案

Take a look at this

<hibernate-mapping>
    <class name="com.vaannila.student.Student" table="STUDENT">
        <meta attribute="class-description">This class contains student details.</meta>
        <id name="studentId" type="long" column="STUDENT_ID">
            <generator class="native" />
        </id>
        <property name="studentName" type="string" length="100" not-null="true" column="STUDENT_NAME" />
        <set name="courses" table="STUDENT_COURSE" cascade="all">
            <key column="STUDENT_ID" />
            <many-to-many column="COURSE_ID"  class="com.vaannila.student.Course" />
        </set>
    </class>
</hibernate-mapping>

<hibernate-mapping>
    <class name="com.vaannila.student.Course" table="COURSE">
        <meta attribute="class-description">This class contains course details.</meta>
        <id name="courseId" type="long" column="COURSE_ID">
            <generator class="native"/>
        </id>
        <property name="courseName" type="string" column="COURSE_NAME"/>
        <set name="students" table="STUDENT_COURSE" cascade="all">
            <key column="COURSE_ID" />
            <many-to-many column="STUDENT_ID"  class="com.vaannila.student.Student" />
        </set>
    </class>
</hibernate-mapping>

Well if you mirror the set in the other class like this doesn't it work?

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