"Learning Notes" Hibernate annotations (y2-1-9)

Hibernate annotations

1. What is an annotation
To hit other types of type metadata on a class or on a method

@ Flag

Used Annotations:

@override Method Overrides

@Test Junit Unit Tests

@Before Unit Tests

@After Unit Tests

Frequently used annotations in hibernate

[EMAIL protected] Declare a class as a persisted class
[email protected] declares the identity property of a persisted class
[Email protected] Defines a build policy that identifies the value of a property, which defaults to native
[Email protected] mapping properties to classes
[Email protected] Persistent class map specified table
[email protected] ignore these properties

Hibernate can use a small configuration file to correlate the mappings, or you can use annotations.

1. One-to-one correlation

A man human has a social security number. Identity a social security number belongs to only one person

Entity classes are as follows

@Entity @table Public classHuman {PrivateInteger hid; @ColumnPrivateString Hname; Privateidentity Identity; @OneToOne @JoinColumn (Name= "IID")     PublicIdentity getidentity () {returnidentity; }     Public voidsetidentity (Identity identity) { This. Identity =identity; } @Id @GeneratedValue PublicInteger Gethid () {returnhid; }     Public voidSethid (Integer hid) { This. HID =hid; }     PublicString Gethname () {returnHname; }     Public voidsethname (String hname) { This. Hname =Hname; }}

@Entity @table Public classIdentity {PrivateInteger IID; PrivateString Inum; PrivateHuman Human; @OneToOne (Mappedby= "Identity", Cascade =Cascadetype.all) PublicHuman Gethuman () {returnHuman; }     Public voidSethuman (Human Human) { This. Human =Human; } @Id @GeneratedValue PublicInteger getiid () {returnIID; }     Public voidsetiid (Integer iid) { This. IID =IID; }     PublicString Getinum () {returnInum; }     Public voidSetinum (String inum) { This. Inum =Inum; }}

Test as follows

@Test      Public void Insert () {        new  Identity ();        Id.setinum ("1231231212123");         New Human ();        Human.sethname ("Ghost");        Human.setidentity (ID);        Id.sethuman (human);        Session.save (human);        Session.save (ID);    }

2. Bidirectional one-to-many association

A Department dept has multiple employees EMP an employee can only belong to one department

Entity classes are as follows

@Entity @table (name= "DEPT3") Public classDept {@Id @GeneratedValuePrivateInteger DeptID; PrivateString dname; @OneToMany (Mappedby= "Dept", Cascade ={Cascadetype.all})Privateset<emp> Emps =NewHashset<emp>();  PublicInteger Getdeptid () {returnDeptID; }     Public voidSetdeptid (Integer deptid) { This. DeptID =DeptID; }     PublicString Getdname () {returndname; }     Public voidsetdname (String dname) { This. dname =dname; }     PublicSet<emp>Getemps () {returnEmps; }     Public voidSetemps (set<emp>emps) {         This. Emps =Emps; }}

@Entity @table (name= "Emp3") Public classEmp {@Id @GeneratedValuePrivateInteger Eid; PrivateString ename; @ManyToOne @JoinColumn (Name= "DeptID")    PrivateDept Dept;  PublicInteger Geteid () {returnEid; }     Public voidSeteid (Integer Eid) { This. Eid =Eid; }     PublicString Getename () {returnename; }     Public voidsetename (String ename) { This. ename =ename; }     PublicDept getdept () {returnDept; }     Public voidsetdept (Dept Dept) { This. Dept =Dept; }}

Test as follows

@Test      Public void Insert () {        new  Dept ();        Dept.setdname ("Ghost Animal Ministry");         New Emp ();        Emp1.setename ("Destiny");        Emp1.setdept (dept);         New Emp ();        Emp2.setename ("Swatch");        Emp2.setdept (dept);        SetNew hashset<emp>();        Set.add (EMP1);        Set.add (EMP2);        Dept.setemps (set);        Session.save (dept);    }

3. Many-to-many associations

One player player can play multiple game games a game can be played by multiple players

Entity classes are as follows

@Entity @table Public classGame {@Id @GeneratedValuePrivateInteger GID; PrivateString Gname; @ManyToMany (Cascade=cascadetype.all) @JoinTable (name= "", Joincolumns= {@JoinColumn (name = "GID")}, Inversejoincolumns= {@JoinColumn (name = "pid"))})    PrivateSet<player> players =NewHashset<player>();  PublicInteger Getgid () {returnGID; }     Public voidSetGid (Integer gid) { This. GID =GID; }     PublicString Getgname () {returnGname; }     Public voidsetgname (String gname) { This. Gname =Gname; }     PublicSet<player>getplayers () {returnplayers; }     Public voidSetplayers (set<player>players) {         This. Players =players; }}

@Entity @table Public classPlayer {@Id @GeneratedValuePrivateInteger pid; PrivateString pname; @ManyToMany (Cascade= Cascadetype.all, Mappedby = "Players")    Privateset<game> games =NewHashset<game>();  PublicInteger getpid () {returnpid; }     Public voidsetpid (Integer pid) { This. PID =pid; }     PublicString Getpname () {returnpname; }     Public voidsetpname (String pname) { This. pname =pname; }     PublicSet<game>Getgames () {returnGames ; }     Public voidSetgames (set<game>Games ) {         This. games =Games ; }}

Test as follows

@Test Public voidInsert () {Game G1=NewGame (); G1.setgname ("My class."); Game G2=NewGame (); G2.setgname ("The Heart of Thanksgiving"); Player P1=NewPlayer (); P1.setpname ("Chara"); Player P2=NewPlayer (); P2.setpname ("Frisk");        G1.getplayers (). Add (p1);        G1.getplayers (). Add (p2);        G2.getplayers (). Add (p1);        G2.getplayers (). Add (p2);        Session.save (G1);    Session.save (G2); }

"Learning Notes" Hibernate annotations (y2-1-9)