Hibernate relationship Mapping (many-to-many)

Many-to-many relationships (student student, course course)

The definition of student class and the configuration of HBM files are as follows

1  Public class Student {2     Private int ID; 3     Private String name; 4     Private New Hashset<course>(); 5 }

1 <?XML version= "1.0" encoding= "UTF-8"?>2 <!DOCTYPE hibernate-mapping Public3 "-//hibernate/hibernate Mapping DTD 3.0//en"4 "Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">5 <hibernate-mapping>6     <classname= "Com.zlt.hibernatedemo.Student"Table= "Student">7         <IDname= "id"column= "id">8             <Generatorclass= "Increment"></Generator>9         </ID>Ten          One         < Propertyname= "Name"type= "Java.lang.String">   A             <columnname= "Name"length= " the" />   -         </ Property> -          the         <Setname= "Courses"Table= "Score"Cascade= "All"> -             <Keycolumn= "StudentID"></Key> -             <Many-to-manyclass= "Com.zlt.hibernatedemo.Course"column= "CourseID"/> -         </Set> +     </class> -  + </hibernate-mapping>

The definition of course class and the configuration of HBM files are as follows

1  Public class Course {2     Private int ID; 3     Private String Coursename; 4     Private New Hashset<student>(); 5 }

1 <?XML version= "1.0" encoding= "UTF-8"?>2 <!DOCTYPE hibernate-mapping Public3 "-//hibernate/hibernate Mapping DTD 3.0//en"4 "Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">5 <hibernate-mapping>6     <classname= "Com.zlt.hibernatedemo.Course"Table= "Course">7         <IDname= "id"column= "id">8             <Generatorclass= "Increment"></Generator>9         </ID>Ten          One         < Propertyname= "Coursename"></ Property> A          -         <Setname= "Students"Table= "Score"> -             <Keycolumn= "CourseID"></Key> the             <Many-to-manyclass= "Com.zlt.hibernatedemo.Student"column= "StudentID"/> -         </Set> -          -     </class> +  - </hibernate-mapping>

Test program

1  Public classHibernatetest {2      Public Static voidMain (string[] args) {3Session session =hibernatefactory.currentsession ();4Transaction tx =session.begintransaction ();5         6         7Student Student1 =NewStudent ();8Student1.setname ("Student1");9         TenStudent Student2 =NewStudent (); OneStudent2.setname ("Student2"); A          -Course course1 =NewCourse (); -Course1.setcoursename ("Course1"); the          -Course Course2 =NewCourse (); -Course2.setcoursename ("Course2"); -          +         //because the default inverse (false) is used, both sides can maintain association relationships - student1.getcourses (). Add (course1); + student1.getcourses (). Add (COURSE2); A          at  - Session.save (student1); -         //student Cascade is set, so no additional insertions are required course - //Session.save (COURSE1); - //Session.save (COURSE2); -          in tx.commit (); - session.close (); to          +     } -}

Results

If there are other attributes in many-to-many auxiliary tables, you have to split the many-to-many relationship into two one-to-many relationships

Student Student

1  Public class Student {2     Private int ID; 3     Private String name; 4     Private New Hashset<score>();     5 }

Course Course

1  Public class Course {2     Private int ID; 3     Private String Coursename; 4     Private New Hashset<score>(); 5 }

Score Score

1  Public classScore {2     Private intID;3     PrivateStudent Student;4     PrivateCourse Course;5     6     //Additional Properties7     Private intscore;8}