举例讲解Java的Hibernate框架中的多对一和一对多映射

create table EMPLOYEE (  id INT NOT NULL auto_increment,  first_name VARCHAR(20) default NULL,  last_name VARCHAR(20) default NULL,  salary   INT default NULL,  address  INT NOT NULL,  PRIMARY KEY (id));

create table ADDRESS (  id INT NOT NULL auto_increment,  street_name VARCHAR(40) default NULL,  city_name VARCHAR(40) default NULL,  state_name VARCHAR(40) default NULL,  zipcode VARCHAR(10) default NULL,  PRIMARY KEY (id));

import java.util.*;public class Employee{  private int id;  private String firstName;   private String lastName;    private int salary;  private Address address;  public Employee() {}  public Employee(String fname, String lname,           int salary, Address address ) {   this.firstName = fname;   this.lastName = lname;   this.salary = salary;   this.address = address;  }  public int getId() {   return id;  }  public void setId( int id ) {   this.id = id;  }  public String getFirstName() {   return firstName;  }  public void setFirstName( String first_name ) {   this.firstName = first_name;  }  public String getLastName() {   return lastName;  }  public void setLastName( String last_name ) {   this.lastName = last_name;  }  public int getSalary() {   return salary;  }  public void setSalary( int salary ) {   this.salary = salary;  }  public Address getAddress() {   return address;  }  public void setAddress( Address address ) {   this.address = address;  }}

import java.util.*;public class Address{  private int id;  private String street;     private String city;     private String state;    private String zipcode;   public Address() {}  public Address(String street, String city,          String state, String zipcode) {   this.street = street;    this.city = city;    this.state = state;    this.zipcode = zipcode;   }  public int getId() {   return id;  }  public void setId( int id ) {   this.id = id;  }  public String getStreet() {   return street;  }  public void setStreet( String street ) {   this.street = street;  }  public String getCity() {   return city;  }  public void setCity( String city ) {   this.city = city;  }  public String getState() {   return state;  }  public void setState( String state ) {   this.state = state;  }  public String getZipcode() {   return zipcode;  }  public void setZipcode( String zipcode ) {   this.zipcode = zipcode;  }  }

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC  "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping>  <class name="Employee" table="EMPLOYEE">   <meta attribute="class-description">     This class contains the employee detail.    </meta>   <id name="id" type="int" column="id">     <generator class="native"/>   </id>   <property name="firstName" column="first_name" type="string"/>   <property name="lastName" column="last_name" type="string"/>   <property name="salary" column="salary" type="int"/>   <many-to-one name="address" column="address"     class="Address" not-null="true"/>  </class>  <class name="Address" table="ADDRESS">   <meta attribute="class-description">     This class contains the address detail.    </meta>   <id name="id" type="int" column="id">     <generator class="native"/>   </id>   <property name="street" column="street_name" type="string"/>   <property name="city" column="city_name" type="string"/>   <property name="state" column="state_name" type="string"/>   <property name="zipcode" column="zipcode" type="string"/>  </class></hibernate-mapping>

import java.util.*; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.Transaction;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class ManageEmployee {  private static SessionFactory factory;   public static void main(String[] args) {   try{     factory = new Configuration().configure().buildSessionFactory();   }catch (Throwable ex) {      System.err.println("Failed to create sessionFactory object." + ex);     throw new ExceptionInInitializerError(ex);    }   ManageEmployee ME = new ManageEmployee();   /* Let us have one address object */   Address address = ME.addAddress("Kondapur","Hyderabad","AP","532");   /* Add employee records in the database */   Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, address);   /* Add another employee record in the database */   Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, address);   /* List down all the employees */   ME.listEmployees();   /* Update employee's salary records */   ME.updateEmployee(empID1, 5000);   /* Delete an employee from the database */   ME.deleteEmployee(empID2);   /* List down all the employees */   ME.listEmployees();  }  /* Method to add an address record in the database */  public Address addAddress(String street, String city,                String state, String zipcode) {   Session session = factory.openSession();   Transaction tx = null;   Integer addressID = null;   Address address = null;   try{     tx = session.beginTransaction();     address = new Address(street, city, state, zipcode);     addressID = (Integer) session.save(address);      tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }   return address;  }  /* Method to add an employee record in the database */  public Integer addEmployee(String fname, String lname,                int salary, Address address){   Session session = factory.openSession();   Transaction tx = null;   Integer employeeID = null;   try{     tx = session.beginTransaction();     Employee employee = new Employee(fname, lname, salary, address);     employeeID = (Integer) session.save(employee);      tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }   return employeeID;  }  /* Method to list all the employees detail */  public void listEmployees( ){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     List employees = session.createQuery("FROM Employee").list();      for (Iterator iterator =               employees.iterator(); iterator.hasNext();){      Employee employee = (Employee) iterator.next();       System.out.print("First Name: " + employee.getFirstName());       System.out.print(" Last Name: " + employee.getLastName());       System.out.println(" Salary: " + employee.getSalary());      Address add = employee.getAddress();      System.out.println("Address ");      System.out.println(" Street: " + add.getStreet());      System.out.println(" City: " + add.getCity());      System.out.println(" State: " + add.getState());      System.out.println(" Zipcode: " + add.getZipcode());     }     tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }  /* Method to update salary for an employee */  public void updateEmployee(Integer EmployeeID, int salary ){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     Employee employee =           (Employee)session.get(Employee.class, EmployeeID);      employee.setSalary( salary );     session.update(employee);     tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }  /* Method to delete an employee from the records */  public void deleteEmployee(Integer EmployeeID){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     Employee employee =           (Employee)session.get(Employee.class, EmployeeID);      session.delete(employee);      tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }}

$java ManageEmployee

.......VARIOUS LOG MESSAGES WILL DISPLAY HERE........First Name: Manoj Last Name: Kumar Salary: 4000Address    Street: Kondapur    City: Hyderabad    State: AP    Zipcode: 532First Name: Dilip Last Name: Kumar Salary: 3000Address    Street: Kondapur    City: Hyderabad    State: AP    Zipcode: 532First Name: Manoj Last Name: Kumar Salary: 5000Address    Street: Kondapur    City: Hyderabad    State: AP    Zipcode: 532

mysql> select * from EMPLOYEE;

+----+------------+-----------+--------+---------+| id | first_name | last_name | salary | address |+----+------------+-----------+--------+---------+| 1 | Manoj   | Kumar   |  5000 | 5    |+----+------------+-----------+--------+---------+1 row in set (0.00 sec)

mysql> select * from ADDRESS;

+----+-------------+-----------+------------+---------+| id | street_name | city_name | state_name | zipcode |+----+-------------+-----------+------------+---------+| 1 | Kondapur  | Hyderabad | AP     | 532   |+----+-------------+-----------+------------+---------+1 row in set (0.00 sec)

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC  "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping>  <class name="Employee" table="EMPLOYEE">   <meta attribute="class-description">     This class contains the employee detail.    </meta>   <id name="id" type="int" column="id">     <generator class="native"/>   </id>   <set name="certificates" cascade="all">     <key column="employee_id"/>     <one-to-many class="Certificate"/>   </set>   <property name="firstName" column="first_name" type="string"/>   <property name="lastName" column="last_name" type="string"/>   <property name="salary" column="salary" type="int"/>  </class>  <class name="Certificate" table="CERTIFICATE">   <meta attribute="class-description">     This class contains the certificate records.    </meta>   <id name="id" type="int" column="id">     <generator class="native"/>   </id>   <property name="name" column="certificate_name" type="string"/>  </class></hibernate-mapping>

import java.util.*; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.Transaction;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class ManageEmployee {  private static SessionFactory factory;   public static void main(String[] args) {   try{     factory = new Configuration().configure().buildSessionFactory();   }catch (Throwable ex) {      System.err.println("Failed to create sessionFactory object." + ex);     throw new ExceptionInInitializerError(ex);    }   ManageEmployee ME = new ManageEmployee();   /* Let us have a set of certificates for the first employee */   HashSet set1 = new HashSet();   set1.add(new Certificate("MCA"));   set1.add(new Certificate("MBA"));   set1.add(new Certificate("PMP"));      /* Add employee records in the database */   Integer empID1 = ME.addEmployee("Manoj", "Kumar", 4000, set1);   /* Another set of certificates for the second employee */   HashSet set2 = new HashSet();   set2.add(new Certificate("BCA"));   set2.add(new Certificate("BA"));   /* Add another employee record in the database */   Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, set2);   /* List down all the employees */   ME.listEmployees();   /* Update employee's salary records */   ME.updateEmployee(empID1, 5000);   /* Delete an employee from the database */   ME.deleteEmployee(empID2);   /* List down all the employees */   ME.listEmployees();  }  /* Method to add an employee record in the database */  public Integer addEmployee(String fname, String lname,                       int salary, Set cert){   Session session = factory.openSession();   Transaction tx = null;   Integer employeeID = null;   try{     tx = session.beginTransaction();     Employee employee = new Employee(fname, lname, salary);     employee.setCertificates(cert);     employeeID = (Integer) session.save(employee);      tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }   return employeeID;  }  /* Method to list all the employees detail */  public void listEmployees( ){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     List employees = session.createQuery("FROM Employee").list();      for (Iterator iterator1 =               employees.iterator(); iterator1.hasNext();){      Employee employee = (Employee) iterator1.next();       System.out.print("First Name: " + employee.getFirstName());       System.out.print(" Last Name: " + employee.getLastName());       System.out.println(" Salary: " + employee.getSalary());      Set certificates = employee.getCertificates();      for (Iterator iterator2 =              certificates.iterator(); iterator2.hasNext();){         Certificate certName = (Certificate) iterator2.next();          System.out.println("Certificate: " + certName.getName());       }     }     tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }  /* Method to update salary for an employee */  public void updateEmployee(Integer EmployeeID, int salary ){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     Employee employee =           (Employee)session.get(Employee.class, EmployeeID);      employee.setSalary( salary );     session.update(employee);     tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }  /* Method to delete an employee from the records */  public void deleteEmployee(Integer EmployeeID){   Session session = factory.openSession();   Transaction tx = null;   try{     tx = session.beginTransaction();     Employee employee =           (Employee)session.get(Employee.class, EmployeeID);      session.delete(employee);      tx.commit();   }catch (HibernateException e) {     if (tx!=null) tx.rollback();     e.printStackTrace();    }finally {     session.close();    }  }}

$java ManageEmployee

.......VARIOUS LOG MESSAGES WILL DISPLAY HERE........First Name: Manoj Last Name: Kumar Salary: 4000Certificate: MBACertificate: PMPCertificate: MCAFirst Name: Dilip Last Name: Kumar Salary: 3000Certificate: BCACertificate: BAFirst Name: Manoj Last Name: Kumar Salary: 5000Certificate: MBACertificate: PMPCertificate: MCA

mysql> select * from employee;

+----+------------+-----------+--------+| id | first_name | last_name | salary |+----+------------+-----------+--------+| 1 | Manoj   | Kumar   |  5000 |+----+------------+-----------+--------+1 row in set (0.00 sec)

mysql> select * from certificate;

+----+------------------+-------------+| id | certificate_name | employee_id |+----+------------------+-------------+| 1 | MBA       |     1 || 2 | PMP       |     1 || 3 | MCA       |     1 |+----+------------------+-------------+3 rows in set (0.00 sec)