• Hibernate ManyToOne Mappings 多对一关联映射


    Hibernate ManyToOne Mappings 多对一关联映射


    Hibernate框架的使用步骤:
    1、创建Hibernate的配置文件(hibernate.cfg.xml)
    2、创建持久化类,即事实上例须要保存到数据库中的类(Employee.java)
    3、创建对象-关系映射文件(Employee.hbm.xml)

    4、通过Hibernate API编写訪问数据库的代码


    样例:多个员工相应一个地址。


    一、创建hibernate.cfg.xml 配置文件:

    注意数据库名、用户名、密码是否填写正确。


    <?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 testone is the database name --> <property name="hibernate.connection.url">jdbc:mysql://localhost/testMany2One</property> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">root</property> <property name="hibernate.show_sql">true</property> <!-- List of XML mapping files --> <mapping resource="resource/Employee.hbm.xml" /> </session-factory> </hibernate-configuration>




    二、创建持久化类。即事实上例须要保存到数据库中的类(Employee.java、Address.java)

    Employee.java
    package com.jiangge.hblearn;
    
    /**
     * @author jiangge
     */
    public class Employee
    {
    	private int id;
    	private String firstName;
    	private String lastName;
    	private int salary;
    	private Address address;
    
    	public Employee()
    	{
    	}
    
    	public Employee(String firstName, String lastName, int salary,
    			Address address)
    	{
    		this.firstName = firstName;
    		this.lastName = lastName;
    		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 firstName)
    	{
    		this.firstName = firstName;
    	}
    
    	public String getLastName()
    	{
    		return lastName;
    	}
    
    	public void setLastName(String lastName)
    	{
    		this.lastName = lastName;
    	}
    
    	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;
    	}
    }
    



    Address.java
    package com.jiangge.hblearn;
    
    /**
     * @author shijiangge
     * @version 2014-7-4 上午11:05:39
     * 
     */
    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;
    	}
    }
    


    在MySQL中创建表:

    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)
    );



    三、创建对象-关系映射文件(Employee.hbm.xml)
    <?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 Many-to-One 关联关系:
    非常多员工能够相应一个地址。
    
    
    0基础的程序猿手写 Employee.hbm.xml 映射文件,而高级程序猿使用XDoclet, Middlegen and AndroMDA这些技术,自己主动生成映射文件。
    
    meta 标签是可选的,用来描写叙述类。
    
    Hibernate的主键生成策略:
    【identity】採用数据库提供的主键生成机制。

    如DB2、SQL Server、MySQL 中的主键生成机制。

    【native】由 Hibernate 依据使用的数据库自行推断採用 identity、hilo、sequence 当中一种作为主键生成方式。

    --> <hibernate-mapping> <class name="com.jiangge.hblearn.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="com.jiangge.hblearn.Address" not-null="true" /> </class> <class name="com.jiangge.hblearn.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>




    四、通过Hibernate API编写訪问数据库的代码

    package test;
    
    import java.util.*;
    
    import org.hibernate.HibernateException;
    import org.hibernate.Session;
    import org.hibernate.Transaction;
    import org.hibernate.SessionFactory;
    import org.hibernate.cfg.Configuration;
    
    import com.jiangge.hblearn.Address;
    import com.jiangge.hblearn.Employee;
    
    /**
     * 測试类:CRUD操作
     * @author jiangge
     *
     */
    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); //("Manoj", "Kumar", 4000, address);
    
    		/* Add another employee record in the database */
    		Integer empID2 = ME.addEmployee("Dilip", "Kumar", 3000, address);//("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();
    		}
    	}
    }



    五、执行结果:
    mysql>  select * from EMPLOYEE;
    +----+------------+-----------+--------+---------+
    | id | first_name | last_name | salary | address |
    +----+------------+-----------+--------+---------+
    |  1 | Manoj      | Kumar     |   5000 |       1 |
    +----+------------+-----------+--------+---------+
    1 row in set
    
    mysql> select * from ADDRESS;
    +----+-------------+-----------+------------+---------+
    | id | street_name | city_name | state_name | zipcode |
    +----+-------------+-----------+------------+---------+
    |  1 | Kondapur    | Hyderabad | AP         | 532     |
    +----+-------------+-----------+------------+---------+
    1 row in set
    
    mysql> 




    log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
    log4j:WARN Please initialize the log4j system properly.
    Hibernate: insert into ADDRESS (street_name, city_name, state_name, zipcode) values (?, ?

    , ?

    , ?) Hibernate: insert into EMPLOYEE (first_name, last_name, salary, address) values (?, ?, ?

    , ?) Hibernate: insert into EMPLOYEE (first_name, last_name, salary, address) values (?, ?, ?, ?

    ) Hibernate: select employee0_.id as id0_, employee0_.first_name as first2_0_, employee0_.last_name as last3_0_, employee0_.salary as salary0_, employee0_.address as address0_ from EMPLOYEE employee0_ First Name: Manoj Last Name: Kumar Salary: 4000 Address Hibernate: select address0_.id as id1_0_, address0_.street_name as street2_1_0_, address0_.city_name as city3_1_0_, address0_.state_name as state4_1_0_, address0_.zipcode as zipcode1_0_ from ADDRESS address0_ where address0_.id=?

    Street: Kondapur City: Hyderabad State: AP Zipcode: 532 First Name: Dilip Last Name: Kumar Salary: 3000 Address Street: Kondapur City: Hyderabad State: AP Zipcode: 532 Hibernate: select employee0_.id as id0_0_, employee0_.first_name as first2_0_0_, employee0_.last_name as last3_0_0_, employee0_.salary as salary0_0_, employee0_.address as address0_0_ from EMPLOYEE employee0_ where employee0_.id=? Hibernate: update EMPLOYEE set first_name=?, last_name=?, salary=?, address=? where id=? Hibernate: select employee0_.id as id0_0_, employee0_.first_name as first2_0_0_, employee0_.last_name as last3_0_0_, employee0_.salary as salary0_0_, employee0_.address as address0_0_ from EMPLOYEE employee0_ where employee0_.id=? Hibernate: delete from EMPLOYEE where id=?

    Hibernate: select employee0_.id as id0_, employee0_.first_name as first2_0_, employee0_.last_name as last3_0_, employee0_.salary as salary0_, employee0_.address as address0_ from EMPLOYEE employee0_ First Name: Manoj Last Name: Kumar Salary: 5000 Address Hibernate: select address0_.id as id1_0_, address0_.street_name as street2_1_0_, address0_.city_name as city3_1_0_, address0_.state_name as state4_1_0_, address0_.zipcode as zipcode1_0_ from ADDRESS address0_ where address0_.id=? Street: Kondapur City: Hyderabad State: AP Zipcode: 532



    參考文献:

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  • 原文地址:https://www.cnblogs.com/ldxsuanfa/p/10601026.html
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