how to do Composition in unidirectinal one-one

mv.anji@gmail.com · **Joined:** Thu Jun 12, 2008 3:06 pm **Posts:** 1

Hi

i have two tables named

Employee Address

empId empId
empName city
sal street

and i have two java classes named Employee and Address

public class Employee {

private long empId;

private String empName;

private int sal;

private Address address;

// getters and setters

}

public class Address {

private String empId;

private String city;

private String street;

// getters and setters
}

and .hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>

<class name="com.Employee" table="MyEmp1" >
<id name="empId" column="empId">
<generator class="identity"/>
</id>

<property name="empName" column="empName"/>

<property name="sal"/>

<one-to-one name="address" class="com.Address" cascade="all"/>

</class>

<class name="com.Address" table="address">
<id name="empId" column="empId">
<generator class="foreign">
<param name="property">employee</param>
</generator>
</id>
<property name="city" column="city"/>
<property name="address" column="address"/>
<one-to-one name="employee" class="com.Employee" constrained="true"/>
</class>

</hibernate-mapping>

and it is not working for me... how to do it ...

Cameron McKenzie · **Posted:** Thu Jun 12, 2008 4:46 pm

So, you have a one to one with a User and an Address, or a one to many?

I have a little tutorial that maps a one-to-one relationship between an Exam and an ExamDetail. It's a one-to-one.

http://jpa.ezhibernate.com/Javacode/learn.jsp?tutorial=17mappingonetooneassociations

I use annotations, but you just have to find the equivalent xml mapping. With annotations it looks like this:

Code:

@Entity
@Table(name = "exam", schema = "examscam")
public class Exam {
/* @Basic annotation has been
 added to all basic fields*/
 
  private int id;
  private String shortName;

  private ExamDetail detail;

  @Id
  @GeneratedValue
  @Column(name = "id")
  public int getId() { return id; }
  private void setId(int id) {this.id = id;}

 @OneToOne(cascade=CascadeType.ALL,fetch=FetchType.LAZY)
  @JoinColumn(name="detail_id")
  public ExamDetail getDetail() {return detail; }
  public void setDetail(ExamDetail detail) {
    this.detail = detail;
  }   

  @Basic
  public String getShortName() { return shortName;}
  public void setShortName(String shortName) {
    this.shortName = shortName;
  }
}

Now the detail class:

Code:

@Entity
@Table(name = "exam_detail", schema = "examscam")
public class ExamDetail {
/* @Basic annotation has been 
added to all basic fields*/
  private int id;
  private String fullName;
  private int numberOfQuestions;
  private int passingPercentage;  
  private Exam exam;
  
  @Id
  @GeneratedValue
  @Column(name = "id")
  public int getId() {return id;}
  private void setId(int id) {this.id = id;}

  @OneToOne(cascade=CascadeType.ALL, mappedBy="detail")
  public Exam getExam(){return exam;}
  public void setExam(Exam exam){this.exam=exam;}

  @Basic
  public String getFullName() {return fullName;}
  public void setFullName(String fullName) {
    this.fullName = fullName;
  }

  @Basic
  public int getNumberOfQuestions() {
   return numberOfQuestions;
  }
 public void setNumberOfQuestions(int numberOfQuestions){
    this.numberOfQuestions = numberOfQuestions;
  }

  @Basic
  public int getPassingPercentage() {
   return passingPercentage;
  }
  public void setPassingPercentage(int passingPercentage){
    this.passingPercentage = passingPercentage;
  }

Once that's done, running the code is very natural:

Code:

public static void main(String args[]){
  HibernateUtil.recreateDatabase();
  Exam exam = new Exam();
  exam.setShortName("SCJA");

  ExamDetail detail = new ExamDetail();
  detail.setFullName("Sun Certified Java Associate");
  detail.setPassingPercentage(62);
  detail.setNumberOfQuestions(55);
  exam.setDetail(detail);

  Session session = HibernateUtil.beginTransaction();
  //possible due to CascadeType.ALL
  session.save(exam);
  HibernateUtil.commitTransaction();
}

Here's the tutorial if you want to follow through it.

http://jpa.ezhibernate.com/Javacode/learn.jsp?tutorial=17mappingonetooneassociations

You say its not working. Is there a specific exception you are getting that we can use to narrow down the problem?[/url]