Hibernate!! Multi-to-many (unidirectional | bidirectional) Association Mappings

Many-to-many-unidirectional association mappings

1  PackageCom.hb.model;2 3 ImportJava.util.HashSet;4 ImportJava.util.Set;5 6 Importjavax.persistence.Entity;7 ImportJavax.persistence.GeneratedValue;8 Importjavax.persistence.Id;9 ImportJavax.persistence.ManyToMany;Ten Importjavax.persistence.Table; One  A @Entity -@Table (name= "T_teacher") -  Public classTeacher { the     Private  intTid; -     PrivateString Tname; -     Privateset<student> students =NewHashset<student>(); -      + @Id - @GeneratedValue +      Public intGettid () { A         returnTid; at     } -      Public voidSettid (inttid) { -          This. Tid =Tid; -     } -      PublicString Gettname () { -         returnTname; in     } -      Public voidsettname (String tname) { to          This. Tname =Tname; +     } - @ManyToMany the      PublicSet<student>getstudents () { *         returnstudents; $     }Panax Notoginseng      Public voidSetstudents (set<student>students) { -          This. Students =students; the     } +      A      the  +}

 PackageCom.hb.model;Importjavax.persistence.Entity;ImportJavax.persistence.GeneratedValue;Importjavax.persistence.Id;Importjavax.persistence.Table; @Entity @table (name= "T_student") Public classStudent {Private  intSID; PrivateString sname; @Id @GeneratedValue Public intGetSID () {returnSID; }     Public voidSetsid (intSID) {         This. Sid =SID; }     PublicString Getsname () {returnsname; }     Public voidsetsname (String sname) { This. sname =sname; }        }

The resulting table is as follows:

The name of the resulting intermediate table is automatically generated, or you can change the name of the table by adding some properties

Just add some attributes to the teacher class, and the modified code is as follows:

1 @Entity2@Table (name= "T_teacher")3  Public classTeacher {4     Private  intTid;5     PrivateString Tname;6     Privateset<student> students =NewHashset<student>();7     8 @Id9 @GeneratedValueTen      Public intGettid () { One         returnTid; A     } -      Public voidSettid (inttid) { -          This. Tid =Tid; the     } -      PublicString Gettname () { -         returnTname; -     } +      Public voidsettname (String tname) { -          This. Tname =Tname; +     } A @ManyToMany at@JoinTable (name= "t_s",//Table name -joincolumns={@JoinColumn (name= "teacher_id")},//???  -inversejoincolumns={@JoinColumn (name= "student_id")}//The ID of the corresponding foreign key for that table. -         ) -      PublicSet<student>getstudents () { -         returnstudents; in     } -      Public voidSetstudents (set<student>students) { to          This. Students =students; +     } -}

Configuration of a many-to-many one-way association in an XML file

1 <hibernate-mapping>2     <classname= "Com.hb.model.Teacher">3         <IDname= "Tid">4             <Generatorclass= "Native"></Generator>5         </ID>6         7         < Propertyname= "Tname"></ Property>8         <Setname= "Students"Table= "t_s">9             <Keycolumn= "teacher_id"></Key>Ten             <Many-to-manyclass= "com.hb.model. Student "column= "student_id"/> One         </Set> A     </class> -      - </hibernate-mapping>

Many-to-many-bidirectional association mappings

• Rarely used
• The Mappedby is always used in two directions.

Hibernate!! Multi-to-many (unidirectional | bidirectional) Association Mappings