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>

 

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

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