Hibernate 示例

Posted 2020-12-02 阿衰问问

所需jar包（必备包位于lib目录下的required中）

目录结构

1.编写数据库

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,
    PRIMARY KEY (id)
);

2.配置数据库文件---hibernate.cfg.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM 
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
   <session-factory>
   <property name="hibernate.dialect">
      org.hibernate.dialect.mysqlDialect
   </property>
   <property name="hibernate.connection.driver_class">
      com.mysql.jdbc.Driver
   </property>

   <!-- Assume test is the database name -->
   <property name="hibernate.connection.url">
      jdbc:mysql://localhost:3306/test
   </property>
   <property name="hibernate.connection.username">
      root
   </property>
   <property name="hibernate.connection.password">
      
   </property>

   <!-- List of XML mapping files -->
    <mapping resource="com/zhang/entity/Employee.hbm.xml" />

</session-factory>
</hibernate-configuration> 

3.创建持久化类---Employee.java

package com.zhang.entity;

public class Employee{
       private int id;
       private String firstName; 
       private String lastName;   
       private int salary;  

       public Employee() {}
       public Employee(String fname, String lname, int salary) {
          this.firstName = fname;
          this.lastName = lname;
          this.salary = salary;
       }
       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;
       }
    }

4.映射文件---Employee.hbm.xml（将已经定义的类或类组与数据库中的表对应起来）

<?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="com.zhang.entity.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"/>
   </class>
</hibernate-mapping>

5.工具类---HibernateUtil.java（解析配置文件）

 一些固定而且经常使用的步骤我们期望做成一个工具类，以后再需要重复步骤时咱们仅需要引用此工具类就可以，从而避免了一直创建重复代码。比如加载数据库的驱动等，这里Hibernate中我们每个主程序都需要加载hibernate.cfg.xml文件、创建SessionFactory对象、创建Session对象、关闭session。这些都是固定化的步骤，因此我们将它们写在工具类HibernateUtil中，以后咱们直接引用此文件创建各对象即可，大大减少了代码量，提高了代码复用性。

package com.zhang.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
 
public final class HibernateUtil {
    private HibernateUtil(){        
    }
    private static SessionFactory sessionFactory;
    static{
        Configuration cfg = new Configuration();
        cfg.configure();
        ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(cfg.getProperties()).build();
        sessionFactory = cfg.buildSessionFactory(sr);
    }
    public static SessionFactory getSeesionFactory(){
        return sessionFactory;
    }
    public static Session getSession(){
        return sessionFactory.openSession();
    }
 
}

6.测试类---ManageEmployee.java（与数据库连接）

Session 用于获取与数据库的物理连接。 Session 对象是轻量级的，并且设计为在每次需要与数据库进行交互时被实例化。持久态对象被保存，并通过 Session 对象检索找回。

Session session = factory.openSession();
Transaction tx = null;
try {
   tx = session.beginTransaction();
   // do some work
   ...
   tx.commit();
}
catch (Exception e) {
   if (tx!=null) tx.rollback();
   e.printStackTrace(); 
}finally {
   session.close();
}

package com.zhang.test;
import java.util.List; 
import java.util.Date;
import java.util.Iterator; 

import org.hibernate.HibernateException; 
import org.hibernate.Session; 
import org.hibernate.Transaction;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

import com.zhang.entity.Employee;

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();

      /* Add few employee records in database */
      Integer empID1 = ME.addEmployee("Zara", "Ali", 1000);
      Integer empID2 = ME.addEmployee("Daisy", "Das", 5000);
      Integer empID3 = ME.addEmployee("John", "Paul", 10000);

      /* List down all the employees */
      ME.listEmployees();

      /* Update employee\'s records */
      ME.updateEmployee(empID1, 5000);

      /* Delete an employee from the database */
      ME.deleteEmployee(empID2);

      /* List down new list of the employees */
      ME.listEmployees();
   }
   /* Method to CREATE an employee in the database */
   public Integer addEmployee(String fname, String lname, int salary){
      Session session = factory.openSession();
      Transaction tx = null;
      Integer employeeID = null;
      try{
         tx = session.beginTransaction();
         Employee employee = new Employee(fname, lname, salary);
         employeeID = (Integer) session.save(employee); 
         tx.commit();
      }catch (HibernateException e) {
         if (tx!=null) tx.rollback();
         e.printStackTrace(); 
      }finally {
         session.close(); 
      }
      return employeeID;
   }
   /* Method to  READ all the employees */
   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()); 
         }
         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(); 
      }
   }
}

 

 

Hibernate 教程