Hibernate -- A unidirectional one-to-one association on a foreign key

at sometime we usually need to create two tables that one table relate another.Such as a husband only

have a wife. So how can I design relationship like this.In programming, The type of this relationship

named “unidirectional one-to-one association”.

How to implement this relationship with hibernate?

example for husband and wife.

When create object husband and wife, you can relate two object like this:

The Hasband object:

   1:  @Entity

   2:  public class Husband {

   3:      private int id;

   4:      private String name;

   5:      private Wife wife;

   6:      @Id

   7:      @GeneratedValue

   8:      public int getId() {

   9:          return id;

  10:      }

  11:      public void setId(int id) {

  12:          this.id = id;

  13:      }

  14:      public String getName() {

  15:          return name;

  16:      }

  17:      public void setName(String name) {

  18:          this.name = name;

  19:      }

  20:      @OneToOne

  21:      @JoinColumn(name="wifeId")

  22:      public Wife getWife() {

  23:          return wife;

  24:      }

  25:      public void setWife(Wife wife) {

  26:          this.wife = wife;

  27:      }

  28:  }

The Wife object:

   1:  @Entity

   2:  public class Wife {

   3:      private int id;

   4:      private String name;

   5:      @Id

   6:      @GeneratedValue

   7:      public int getId() {

   8:          return id;

   9:      }

  10:      public void setId(int id) {

  11:          this.id = id;

  12:      }

  13:      public String getName() {

  14:          return name;

  15:      }

  16:      public void setName(String name) {

  17:          this.name = name;

  18:      }

  19:      

  20:  }

We use annotation configuration hibernate by default. So you saw the annotition like @Entity in code.

Wife and Husband both are used @Entity.It means that object will mapping to database.

The getId() method in Wife and Husband both are used @Id and @GeneratedValue

The getWife() method in Husband object has annotation like this:

@OneToOne
      @JoinColumn(name="wifeId")

Then, the column which is named wifeId wille be created.

So, Use annotation is so simple.  that;s all.

Do from that we can get create table SQL like this:

   1:      create table Husband (

   2:          id integer not null auto_increment,

   3:          name varchar(255),

   4:          wifeId integer,

   5:          primary key (id)

   6:      )

   7:  2014-1-11 14:46:41 org.hibernate.tool.hbm2ddl.SchemaExport perform

   8:  

   9:   

  10:      create table Wife (

  11:          id integer not null auto_increment,

  12:          name varchar(255),

  13:          primary key (id)

  14:      )

  15:   

  16:      alter table Husband 

  17:          add constraint FK_kruq9jfxa0jrc2od8dbh09mia 

  18:          foreign key (wifeId) 

  19:          references Wife (id)

Finally , Talk about xml configure. When use xml to configure hibernate more trouble than use annotations:

You need write like this in xml file:

<many-to-one name="wife" column="wifId" unique="true" ></many-to-one>