Hibernate Learning Notes _ relational Mapping _ Other

Collection mappings (less important)

1 Set

2 List (almost multiple @orderby with set)

A) @OrderBy sort

Private New Arraylist<user>();        @OneToMany (Mappedby= "group",            cascade={cascadetype.all}            )    @OrderBy ("Name ASC" )    public list<user> getusers () {         return  users;    }      Public void setusers (list<user> users) {        this. Users = users;    } 

3 Map

A) @Mapkey

Private New Hashmap<integer, user>();        @OneToMany (Mappedby= "group", cascade=cascadetype.all)    @MapKey (name= "id")      public Map<integer, user> getusers () {        return  users;    }      Public void setusers (Map<integer, user> users) {        this. Users= users;    } 

@Test      Public void Testloadgroup () {                        = sessionfactory.getcurrentsession ();        S.begintransaction ();        Group G = (group) s.load (group).  Class, 1);          for (Map.entry<integer, user> entry:g.getusers (). EntrySet ()) {            System.out.println (Entry.getvalue ()). GetName ());        }         s.gettransaction (). commit ();            }

Inheritance mappings (less important)

13 Different ways

A) a summary table single_table (a table is generated in the database)

@Entity @inheritance (Strategy=inheritancetype.single_table) @DiscriminatorColumn (name= "Discriminator", discriminatortype=discriminatortype.string) @DiscriminatorValue ("Person") Public classPerson {Private intID; PrivateString name; @Id @GeneratedValue Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }}

  @Entity @discriminatorvalue ( "student" )  public  class  Student extends   person { private  int   score;  public  int   Getscore () {  score;  public  void  SetScore (int   score) { this . Score = score; }    }

@Entity @discriminatorvalue ("Teacher")  Public class extends Person {    private  String title;      Public String GetTitle () {        return  title;    }      Public void Settitle (String title) {        this. title = title;    }    } 

@Test Public voidTestsave () {Student s=NewStudent (); S.setname ("S1"); S.setscore (80); Teacher T=NewTeacher (); T.setname ("T1"); T.settitle (Intermediate); Session Session=sessionfactory.opensession ();        Session.begintransaction ();        Session.save (s);        Session.save (t);        Session.gettransaction (). commit ();    Session.close (); } @Test Public voidtestLoad () {testsave (); Session Session=sessionfactory.opensession ();        Session.begintransaction (); Student s= (Student) session.load (Student.class, 1);        System.out.println (S.getscore ()); Person P= (person) session.load (person).class, 2);        System.out.println (P.getname ());        Session.gettransaction (). commit ();            Session.close (); }

b) One table for each class Table_per_class

@Entity @inheritance (Strategy=inheritancetype.table_per_class) @TableGenerator (name= "T_gen", table= "T_gen_table", Pkcolumnname= "T_PK", Valuecolumnname= "T_value", Pkcolumnvalue= "PERSON_PK", InitialValue=1, Allocationsize=1        ) Public classPerson {Private intID; PrivateString name; @Id @GeneratedValue (Generator= "T_gen", strategy=generationtype.table) Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }}

@Entity  Public class extends Person {        privateint  score;      Public int Getscore () {        return  score;    }      Public void setscore (int  score) {        this. score = score;    }    } 

@Entity  Public class extends Person {    private  String title;      Public String GetTitle () {        return  title;    }      Public void Settitle (String title) {        this. title = title;    }    } 

c) Each sub-Class A table joined

The parent class is annotated @inheritance (Strategy=inheritancetype. JOINED)

@Entity @inheritance (Strategy=inheritancetype.joined) Public classPerson {Private intID; PrivateString name; @Id @GeneratedValue Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }}

Hibernate Learning Notes _ relational Mapping _ Other