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Java的Hibernate框架中复合主键映射的创建和使用教程

作者:zhang_xinxiu

复合主键映射用起来比普通的增加主键字段要复杂,这里我们就来共同学习Java的Hibernate框架中复合主键映射的创建和使用教程,需要的朋友可以参考下

复合主键映射需要在映射配置文件中使用<composite-id>标签,该标签是指将一个类指定为相应的复合主键,它的name属性需要指定类文件中定义的属性值,并在该标签中添加<key-property>子标签。
Note:想要使用复合映射必须要将复合主键放到一个类中,也就是讲复合主键属性和其它属性分到两个类中,并将复合主键的类实现接口Serializable,该接口隶属于java.io。
复合主键的映射关系的主键是由多个列复合而成的,对应到数据表中相当的简单,如下图:

201677100922504.png (572×73)

1、类文件
这里就拿上图的表来作为示例,在表中有两个字段年限和持续时间组合成为表的主键,所以分成的新类分别命名为FiscalYearPeriod和FiscalYearPeriodPK,其中FiscalYearPeriodPK类封装表的主键属性,FiscalYearPeriod类封装其它属性以及FiscalYearPeriodPK类。
1.1 FiscalYearPeriod.java
类中封装有基本的属性,并把FiscalYearPeriodPK类作为属性封装到类中,并在配置文件中配置相应的映射,如下代码:

package com.src.hibernate; 
 
import java.sql.Date; 
 
public class FiscalYearPeriod { 
   
  //时间主键 
  private FiscalYearPeriodPK fiscalYearPeriodPK; 
  public FiscalYearPeriodPK getFiscalYearPeriodPK() { 
    return fiscalYearPeriodPK; 
  } 
  public void setFiscalYearPeriodPK(FiscalYearPeriodPK fiscalYearPeriodPK) { 
    this.fiscalYearPeriodPK = fiscalYearPeriodPK; 
  } 
   
  //开始日期 
  private Date beginDate; 
  public Date getBeginDate() { 
    return beginDate; 
  } 
  public void setBeginDate(Date beginDate) { 
    this.beginDate = beginDate; 
  } 
   
  //结束日期 
  private Date endDate; 
  public Date getEndDate() { 
    return endDate; 
  } 
  public void setEndDate(Date endDate) { 
    this.endDate = endDate; 
  } 
   
  //阶段时间 
  private String periodSts; 
  public String getPeriodSts() { 
    return periodSts; 
  } 
  public void setPeriodSts(String periodSts) { 
    this.periodSts = periodSts; 
  } 
} 

1.2 FiscalYearPeriodPK.java
封装主键属性,该类是从FiscalYearPeriod类中分离出来的,包含了基本的主键属性,并且需要实现接口Serializable,该类是要映射到配置文件中<composite-id>标签中要指定该类,代码如下:

package com.src.hibernate; 
 
import java.io.Serializable; 
 
public class FiscalYearPeriodPK implements Serializable { 
   
  //年限 
  private int fiscalYear; 
  public int getFiscalYear() { 
    return fiscalYear; 
  } 
  public void setFiscalYear(int fiscalYear) { 
    this.fiscalYear = fiscalYear; 
  } 
 
  //持续时间 
  private int fiscalPeriod; 
  public int getFiscalPeriod() { 
    return fiscalPeriod; 
  } 
 
  public void setFiscalPeriod(int fiscalPeriod) { 
    this.fiscalPeriod = fiscalPeriod; 
  } 
   
} 

 

2、配置文件
这里有个疑问两个类都是哪个需要添加映射文件?因为会使用<composite-id>标签,所以只需要为FiscalYearPeriod类添加映射即可,在该映射文件中添加对应复合主键标签,并在标签中添加对应的主键属性,如下代码:

<?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.src.hibernate.FiscalYearPeriod" table="t_fiscal_year_period_pk"> 
    <composite-id name="fiscalYearPeriodPK"> 
      <key-property name="fiscalYear"></key-property> 
      <key-property name="fiscalPeriod"></key-property> 
    </composite-id> 
    <property name="beginDate" type="date"/> 
    <property name="endDate" type="date"/> 
    <property name="periodSts"/> 
  </class> 
</hibernate-mapping> 

将上面的文件生成对应的数据库表,生成的sql语句如下:

drop table if exists t_fiscal_year_period_pk 
create table t_fiscal_year_period_pk (fiscalYear integer not null, fiscalPeriod integer not null, beginDate date, endDate date, periodSts varchar(255), primary key (fiscalYear, fiscalPeriod)) 

对应的表结构如下图:

201677101003756.png (677×190)

 

3、数据操作
相应的映射文件配置好后,相应的数据操作就变得很简单了,首先从写入数据开始,向数据库中写入数据时会同时把两个类写入到数据库中,所以此时这两个类都必须转化为Transient状态,所以在保存时需要首先将FiscalYearPeriod对象首先保存到数据库中,然后它会自动关联复合属性,将信息保存到数据库中。
3.1 写入操作
写入的操作方法和以前的写入方法相同,需要定义两个对象,然后保存相应的对象信息到数据库中,代码如下:

public void testSave1(){ 
  //声明会话对象 
  Session session=null; 
   
  try{ 
    //获取会话对象 
    session=HibernateUtils.getSession(); 
    //开启会话 
    session.beginTransaction(); 
    //创建复合对象 
    FiscalYearPeriodPK fiscalyearperiodpk=new FiscalYearPeriodPK(); 
    fiscalyearperiodpk.setFiscalPeriod(2014); 
    fiscalyearperiodpk.setFiscalYear(2012); 
     
    //创建对象 
    FiscalYearPeriod fiscalyearperiod=new FiscalYearPeriod(); 
    fiscalyearperiod.setFiscalYearPeriodPK(fiscalyearperiodpk); 
     
    session.save(fiscalyearperiod); 
    //提交会话 
    session.getTransaction().commit(); 
  }catch(Exception e){ 
    e.printStackTrace(); 
    session.getTransaction().rollback(); 
  }finally{ 
    HibernateUtils.closeSession(session); 
  } 
} 

执行相应的测试方法,生成的SQL语句如下:

Hibernate: insert into t_fiscal_year_period_pk (beginDate, endDate, periodSts, fiscalYear, fiscalPeriod) values (?, ?, ?, ?, ?) 
相应的数据库视图:

201677101028658.png (676×95)

3.2 加载操作
相应的加载方法会和以前不同,因为在该表中主键是复合属性,所以需要创建一个类。在加载数据时需要创建主键对象,此时的主键就是一个对象,更需要为对象的属性赋值,这样才能获取对象,代码如下:

public void testLoad1(){ 
  //声明会话对象 
  Session session=null; 
   
  try{ 
    //获取会话对象 
    session=HibernateUtils.getSession(); 
    //开启会话 
    session.beginTransaction(); 
    //创建复合对象 
    FiscalYearPeriodPK fiscalyearperiodpk=new FiscalYearPeriodPK(); 
    fiscalyearperiodpk.setFiscalPeriod(2014); 
    fiscalyearperiodpk.setFiscalYear(2012); 
     
    FiscalYearPeriod fiscalyearperiod=(FiscalYearPeriod)session.load(FiscalYearPeriod.class,fiscalyearperiodpk); 
    System.out.println("开始日期: "+fiscalyearperiod.getBeginDate());  
    //提交会话 
    session.getTransaction().commit(); 
  }catch(Exception e){ 
    e.printStackTrace(); 
    session.getTransaction().rollback(); 
  }finally{ 
    HibernateUtils.closeSession(session); 
  } 
} 

生成的结果,如下:

Hibernate: select fiscalyear0_.fiscalYear as fiscalYear0_0_, fiscalyear0_.fiscalPeriod as fiscalPe2_0_0_, fiscalyear0_.beginDate as beginDate0_0_, fiscalyear0_.endDate as endDate0_0_, fiscalyear0_.periodSts as periodSts0_0_ from t_fiscal_year_period_pk fiscalyear0_ where fiscalyear0_.fiscalYear=? and fiscalyear0_.fiscalPeriod=? 
开始日期: 2013-10-12 

 

4、综合示例
一个规模较大公司的部门表(hibernate_dept_compositePK),由所在区域(area),部门名(name),本部门人数(empCount),组建时间(birthday)等字段组成,我们使用所在区域和部门名做联合主键:
4.1 目标类:Department.java

public class Department { 
 /** 把主键关联属性抽象出来单独写成一个类 */ 
 //private String area; 
 //private String name; 
 /**把主键类对象作为成员变量*/ 
 private DepartmentPK departmentPK; 
 private int empCount; 
 private Date birthday; 

// public String getArea() { 
//  return area; 
// } 
// 
// public void setArea(String area) { 
//  this.area = area; 
// } 
// 
// public String getName() { 
//  return name; 
// } 
// 
// public void setName(String name) { 
//  this.name = name; 
// } 
  
 public int getEmpCount() { 
  return empCount; 
 } 

 public void setEmpCount(int empCount) { 
  this.empCount = empCount; 
 } 

 public Date getBirthday() { 
  return birthday; 
 } 

 public void setBirthday(Date birthday) { 
  this.birthday = birthday; 
 } 

 public DepartmentPK getDepartmentPK() { 
  return departmentPK; 
 } 

 public void setDepartmentPK(DepartmentPK departmentPK) { 
  this.departmentPK = departmentPK; 
 } 

}

4.2主键类:DepartmentPK.java

public class DepartmentPK implements Serializable { 

 private static final long serialVersionUID = -288002855915204255L; 
 private String area; 
 private String name; 
 /** 
  * 覆盖hashCode方法(根据area和name判断) 
  */ 
 //@Override 
 public int hashCode() { 
  final int prime = 31; 
  int result = 1; 
  result = prime * result + ((area == null) ? 0 : area.hashCode()); 
  result = prime * result + ((name == null) ? 0 : name.hashCode()); 
  return result; 
 } 
 /** 
  * 覆盖equals(根据area和name判断) 
  */ 
 @Override 
 public boolean equals(Object obj) { 
  if (this == obj) 
   return true; 
  if (obj == null) 
   return false; 
  if (getClass() != obj.getClass()) 
   return false; 
  final DepartmentPK other = (DepartmentPK) obj; 
  if (area == null) { 
   if (other.area != null) 
    return false; 
  } else if (!area.equals(other.area)) 
   return false; 
  if (name == null) { 
   if (other.name != null) 
    return false; 
  } else if (!name.equals(other.name)) 
   return false; 
  return true; 
 } 

 public String getArea() { 
  return area; 
 } 

 public void setArea(String area) { 
  this.area = area; 
 } 

 public String getName() { 
  return name; 
 } 

 public void setName(String name) { 
  this.name = name; 
 } 
}

4.3 映射文件Department.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.yangfei.hibernate.compositePk.entity.Department" table="hibernate_dept_compositePK"> 
  <!-- 联合主键 --> 
  <!-- name指的是主键对象属性 --> 
  <composite-id name="departmentPK"> 
   <!-- 这里是主键关联属性 --> 
   <key-property name="area" /> 
   <key-property name="name" /> 
  </composite-id> 
  <!-- 其它属性 --> 
  <property name="empCount" length="4" /> 
  <property name="birthday" type="date" /> 
 </class> 
</hibernate-mapping>

4.4 hibernate配置文件hibernate.cfg.xml

<?xml version='1.0' encoding='UTF-8'?> 
<!DOCTYPE hibernate-configuration PUBLIC 
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 

<!-- Generated by MyEclipse Hibernate Tools.                   --> 
<hibernate-configuration> 
    <session-factory> 
        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property> 
        <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl10</property> 
        <property name="connection.username">scott</property> 
        <property name="connection.password">yf123</property> 
        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property> 
        <property name="hibernate.show_sql">true</property> 
      
     <mapping resource="com/yangfei/hibernate/compositePk/entity/Department.hbm.xml"/> 
    </session-factory> 
</hibernate-configuration>

4.5测试类:DepartmentTest.java

public class DepartmentTest extends TestCase { 
 /** 
  * 测试插入数据 
  */ 
 public void save() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   Department dept = new Department(); 
   /** 生成主键对象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研发部"); 
   dept.setDepartmentPK(deptPK); 

   dept.setEmpCount(100); 
   dept.setBirthday(new Date()); 

   session.save(dept); 
   t.commit(); 
  } catch (HibernateException e) { 
   e.printStackTrace(); 
   t.rollback(); 
  } finally { 
   HibernateUtils.closeSession(session); 
  } 
 } 
 /** 
  * 测试加载数据 
  */ 
 public void load() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主键对象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研发部"); 

   Department dept=(Department)session.load(Department.class, deptPK); 
   System.out.println(dept.getDepartmentPK().getArea()+","+dept.getDepartmentPK().getName()+","+dept.getEmpCount()+","+dept.getBirthday()); 
  } catch (HibernateException e) { 
   e.printStackTrace(); 
   t.rollback(); 
  } finally { 
   HibernateUtils.closeSession(session); 
  } 
 } 
  
 /** 
  * 测试修改数据 
  */ 
 public void update() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主键对象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研发部"); 

   Department emp=(Department)session.load(Department.class, deptPK); 
   System.out.println(emp.getDepartmentPK().getArea()+","+emp.getDepartmentPK().getName()+","+emp.getEmpCount()+","+emp.getBirthday()); 
   emp.setEmpCount(100); 
   session.saveOrUpdate(emp); 
    
   /** 生成主键对象 */ 
   DepartmentPK deptPK2 = new DepartmentPK(); 
   deptPK2.setArea("北京"); 
   deptPK2.setName("研发部"); 
   Department dept=(Department)session.load(Department.class, deptPK2); 
   System.out.println(dept.getDepartmentPK().getArea()+","+dept.getDepartmentPK().getName()+","+dept.getEmpCount()+","+dept.getBirthday()); 
   t.commit(); 
  } catch (HibernateException e) { 
   e.printStackTrace(); 
   t.rollback(); 
  } finally { 
   HibernateUtils.closeSession(session); 
  } 
 } 
  
 /** 
  * 测试删除数据 
  */ 
 public void delete() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主键对象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研发部"); 
    
   Department dept=(Department)session.load(Department.class, deptPK); 
   session.delete(dept); 
   t.commit(); 
  } catch (HibernateException e) { 
   e.printStackTrace(); 
   t.rollback(); 
  } finally { 
   HibernateUtils.closeSession(session); 
  } 
 } 
}

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