Hibernate-----One-to-many association mappings (annotations)

bidirectional 1-n : Usually at the end of the ' one ' Mappedby attribute reversal; give the maintenance end to ' many '

One

Import Javax.persistence.cascadetype;import Javax.persistence.column;import Javax.persistence.entity;import Javax.persistence.generatedvalue;import Javax.persistence.generationtype;import Javax.persistence.Id;import Javax.persistence.onetomany;import javax.persistence.Table; @Entity @table (name = "T_classes") public class classes    Implements Serializable {private int id;     private String name;     Private set<student> students;    @Id @GeneratedValue (strategy = generationtype.auto) public int getId () {return Id;    } public void setId (int id) {this.id = ID;    } @Column (name = "name") public String GetName () {return name;    } public void SetName (String name) {this.name = name; }//Mappedby defined in classes, the classes class will not be responsible for maintaining a cascading relationship. The maintainer is handed over to student. So//1. To assign clsses data to student (student with setclasses () method to bind the class data)//2. When data insertion/update is performed, the last operation is the student (Maintenance side) @OneToMany (cascade = cascadetype.remove, fetch = Fetchtype.lazy, M Appedby = "Classes")    Public set<student> getstudents () {return students;    } public void Setstudents (set<student> students) {this.students = students; }}

Many

Import Javax.persistence.joincolumn;import Javax.persistence.ManyToOne; @Entity @table (name = "T_student") public Class Student implements Serializable {    private int sid;    Private String sname;     Private Classes Classes;     @Id    @GeneratedValue (strategy = generationtype.auto) public    int GetSID () {       return sid;    }     public void Setsid (int sid) {       this.sid = sid;    }     @Column (name = "sname") public    String Getsname () {       return sname;    }     public void Setsname (String sname) {       this.sname = sname;    }     Multiple Cascade:{cascadetype.persist,cascadetype.merge}    //Specifies the foreign key (class_id) @ManyToOne at one end of the many    (cascade = { Cascadetype.all})    @JoinColumn (name = "class_id") public    Classes getclasses () {       return Classes;    } Public     void Setclasses (Classes Classes) {       this.classes = Classes;    }}

because one end maintains the reason why relationships are not maintained at the other end, it is important to avoid using classes that do not maintain relationships in your application . (Class) relationships are established because the relationships are not stored in the database (the non-maintenance side should be saved first, and the maintenance end should be saved)

Hibernate-----One-to-many association mappings (annotations)