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problems persisting primary/foreign keys in 1-N objects/rela

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jakestar

Post subject: problems persisting primary/foreign keys in 1-N objects/rela

Posted: Tue Jun 22, 2010 2:33 am

Newbie

Joined: Tue Jun 22, 2010 2:26 am
Posts: 4

i have two objects, Company and Employee. the relationship between these two objects are one to many (1-N); one Company has many Employees. when i instantiate a Company with a List of Employees, i cannot get the Company.id to persist to the Employee.companyId table/field. can someone tell me what i am doing wrong? my pojos are below.

Code:

package demo.bo;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="employee")
public class Employee {

   @ManyToOne
   @JoinColumn(name="companyId")
   private Company company;
   
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   private int id;
   private String firstName;
   private String lastName;
   
   public Employee() { }
   
   public Employee(String firstName, String lastName) {
      this.firstName = firstName;
      this.lastName = lastName;
   }

   public int getId() {
      return id;
   }

   public void setId(int id) {
      this.id = id;
   }

   public String getFirstName() {
      return firstName;
   }

   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }

   public String getLastName() {
      return lastName;
   }

   public void setLastName(String lastName) {
      this.lastName = lastName;
   }

   public Company getCompany() {
      return company;
   }

   public void setCompany(Company company) {
      this.company = company;
   }
}

Code:

package demo.bo;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.UniqueConstraint;

@Entity
@Table(name="company", uniqueConstraints={@UniqueConstraint(columnNames={"name"})})
public class Company {

   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   @Column(name="id")
   private int id;
   private String name;
   
   @OneToMany(
         mappedBy="company",
         cascade={CascadeType.ALL},
         targetEntity=Employee.class,
         fetch=FetchType.EAGER)
   @JoinColumn(name="companyId")
   private List<Employee> employees;
   
   public Company() { }
   
   public Company(String name) {
      this.name = name;
   }
   
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   
   public void addEmployee(Employee employee) {
      List<Employee> employees = getEmployees();
      employees.add(employee);      
      employee.setCompany(this);
   }

   public List<Employee> getEmployees() {
      if(null == employees) {
         employees = new ArrayList<Employee>();
      }
      return employees;
   }

   public void setEmployees(List<Employee> employees) {
      this.employees = employees;
   }
   
}

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jakestar

Post subject: Re: problems persisting primary/foreign keys in 1-N objects/rela

Posted: Tue Jun 22, 2010 2:42 am

Newbie

Joined: Tue Jun 22, 2010 2:26 am
Posts: 4

here is the logging output. i am using spring + jpa + hibernate + mysql.

Hibernate:
insert
into
company
(name)
values
(?)
Hibernate:
insert
into
employee
(companyId, firstName, lastName)
values
(?, ?, ?)
Jun 22, 2010 2:40:26 AM org.hibernate.util.JDBCExceptionReporter logExceptions
WARNING: SQL Error: 1048, SQLState: 23000
Jun 22, 2010 2:40:26 AM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: Column 'companyId' cannot be null

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jakestar

Post subject: Re: problems persisting primary/foreign keys in 1-N objects/rela

Posted: Tue Jun 22, 2010 2:43 am

Newbie

Joined: Tue Jun 22, 2010 2:26 am
Posts: 4

here is my DDL for the tables.

Code:

drop table if exists employee;
drop table if exists company;

create table company (
   name varchar(100) unique,
   id mediumint not null auto_increment,
   primary key(id),
   index using btree(id)
);

create table employee(
   companyId mediumint not null,
   firstName varchar(100),
   lastName varchar(100),
   id mediumint not null auto_increment,
   primary key(id),
   index using btree(id),
   foreign key FK_COMPANY_ID (companyId) references company(id)
);

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pretham

Post subject: Re: problems persisting primary/foreign keys in 1-N objects/rela

Posted: Tue Jun 22, 2010 3:11 am

Beginner

Joined: Mon Sep 14, 2009 9:29 am
Posts: 30

can you copy and paste your hbm file..i think the problem is with mapping..

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jakestar

Post subject: Re: problems persisting primary/foreign keys in 1-N objects/rela

Posted: Tue Jun 22, 2010 9:50 am

Newbie

Joined: Tue Jun 22, 2010 2:26 am
Posts: 4

i don't have any hibernate XML mapping files at all. everything is annotation driven. at any rate, i found what i was doing wrong. my annotations were correct, but what i wasn't doing was setting the company field for the employee object.

for example, before everything worked, this is what i did.

Code:

Employee employee = new Employee("John", "Doe");
Company company = new Company("Microsoft");
company.getEmployees().add(employee);

to get things to work correctly, i did this (added one line).

Code:

Employee employee = new Employee("John", "Doe");
Company company = new Company("Microsoft");
company.getEmployees().add(employee);
employee.setCompany(company);

for a bidirectional one-to-many multiplicity, upon creation, each object must have a reference to one another.

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