Java的Hibernate框架中復(fù)合主鍵映射的創(chuàng)建和使用教程

更新時(shí)間：2016年07月07日 10:14:46 作者：zhang_xinxiu

復(fù)合主鍵映射用起來比普通的增加主鍵字段要復(fù)雜,這里我們就來共同學(xué)習(xí)Java的Hibernate框架中復(fù)合主鍵映射的創(chuàng)建和使用教程,需要的朋友可以參考下

復(fù)合主鍵映射需要在映射配置文件中使用<composite-id>標(biāo)簽，該標(biāo)簽是指將一個(gè)類指定為相應(yīng)的復(fù)合主鍵，它的name屬性需要指定類文件中定義的屬性值，并在該標(biāo)簽中添加<key-property>子標(biāo)簽。
Note：想要使用復(fù)合映射必須要將復(fù)合主鍵放到一個(gè)類中，也就是講復(fù)合主鍵屬性和其它屬性分到兩個(gè)類中，并將復(fù)合主鍵的類實(shí)現(xiàn)接口Serializable，該接口隸屬于java.io。
復(fù)合主鍵的映射關(guān)系的主鍵是由多個(gè)列復(fù)合而成的，對(duì)應(yīng)到數(shù)據(jù)表中相當(dāng)?shù)暮?jiǎn)單，如下圖：

201677100922504.png (572×73)

1、類文件
這里就拿上圖的表來作為示例，在表中有兩個(gè)字段年限和持續(xù)時(shí)間組合成為表的主鍵，所以分成的新類分別命名為FiscalYearPeriod和FiscalYearPeriodPK，其中FiscalYearPeriodPK類封裝表的主鍵屬性，F(xiàn)iscalYearPeriod類封裝其它屬性以及FiscalYearPeriodPK類。
1.1 FiscalYearPeriod.java
類中封裝有基本的屬性，并把FiscalYearPeriodPK類作為屬性封裝到類中，并在配置文件中配置相應(yīng)的映射，如下代碼：

package com.src.hibernate; 
 
import java.sql.Date; 
 
public class FiscalYearPeriod { 
   
  //時(shí)間主鍵 
  private FiscalYearPeriodPK fiscalYearPeriodPK; 
  public FiscalYearPeriodPK getFiscalYearPeriodPK() { 
    return fiscalYearPeriodPK; 
  } 
  public void setFiscalYearPeriodPK(FiscalYearPeriodPK fiscalYearPeriodPK) { 
    this.fiscalYearPeriodPK = fiscalYearPeriodPK; 
  } 
   
  //開始日期 
  private Date beginDate; 
  public Date getBeginDate() { 
    return beginDate; 
  } 
  public void setBeginDate(Date beginDate) { 
    this.beginDate = beginDate; 
  } 
   
  //結(jié)束日期 
  private Date endDate; 
  public Date getEndDate() { 
    return endDate; 
  } 
  public void setEndDate(Date endDate) { 
    this.endDate = endDate; 
  } 
   
  //階段時(shí)間 
  private String periodSts; 
  public String getPeriodSts() { 
    return periodSts; 
  } 
  public void setPeriodSts(String periodSts) { 
    this.periodSts = periodSts; 
  } 
}

1.2 FiscalYearPeriodPK.java
封裝主鍵屬性，該類是從FiscalYearPeriod類中分離出來的，包含了基本的主鍵屬性，并且需要實(shí)現(xiàn)接口Serializable，該類是要映射到配置文件中<composite-id>標(biāo)簽中要指定該類，代碼如下：

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; 
  } 
 
  //持續(xù)時(shí)間 
  private int fiscalPeriod; 
  public int getFiscalPeriod() { 
    return fiscalPeriod; 
  } 
 
  public void setFiscalPeriod(int fiscalPeriod) { 
    this.fiscalPeriod = fiscalPeriod; 
  } 
   
}

2、配置文件
這里有個(gè)疑問兩個(gè)類都是哪個(gè)需要添加映射文件？因?yàn)闀?huì)使用<composite-id>標(biāo)簽，所以只需要為FiscalYearPeriod類添加映射即可，在該映射文件中添加對(duì)應(yīng)復(fù)合主鍵標(biāo)簽，并在標(biāo)簽中添加對(duì)應(yīng)的主鍵屬性，如下代碼：

<?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>

將上面的文件生成對(duì)應(yīng)的數(shù)據(jù)庫表，生成的sql語句如下：

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))

對(duì)應(yīng)的表結(jié)構(gòu)如下圖：

201677101003756.png (677×190)

3、數(shù)據(jù)操作
相應(yīng)的映射文件配置好后，相應(yīng)的數(shù)據(jù)操作就變得很簡(jiǎn)單了，首先從寫入數(shù)據(jù)開始，向數(shù)據(jù)庫中寫入數(shù)據(jù)時(shí)會(huì)同時(shí)把兩個(gè)類寫入到數(shù)據(jù)庫中，所以此時(shí)這兩個(gè)類都必須轉(zhuǎn)化為Transient狀態(tài)，所以在保存時(shí)需要首先將FiscalYearPeriod對(duì)象首先保存到數(shù)據(jù)庫中，然后它會(huì)自動(dòng)關(guān)聯(lián)復(fù)合屬性，將信息保存到數(shù)據(jù)庫中。
3.1 寫入操作
寫入的操作方法和以前的寫入方法相同，需要定義兩個(gè)對(duì)象，然后保存相應(yīng)的對(duì)象信息到數(shù)據(jù)庫中，代碼如下：

public void testSave1(){ 
  //聲明會(huì)話對(duì)象 
  Session session=null; 
   
  try{ 
    //獲取會(huì)話對(duì)象 
    session=HibernateUtils.getSession(); 
    //開啟會(huì)話 
    session.beginTransaction(); 
    //創(chuàng)建復(fù)合對(duì)象 
    FiscalYearPeriodPK fiscalyearperiodpk=new FiscalYearPeriodPK(); 
    fiscalyearperiodpk.setFiscalPeriod(2014); 
    fiscalyearperiodpk.setFiscalYear(2012); 
     
    //創(chuàng)建對(duì)象 
    FiscalYearPeriod fiscalyearperiod=new FiscalYearPeriod(); 
    fiscalyearperiod.setFiscalYearPeriodPK(fiscalyearperiodpk); 
     
    session.save(fiscalyearperiod); 
    //提交會(huì)話 
    session.getTransaction().commit(); 
  }catch(Exception e){ 
    e.printStackTrace(); 
    session.getTransaction().rollback(); 
  }finally{ 
    HibernateUtils.closeSession(session); 
  } 
}

執(zhí)行相應(yīng)的測(cè)試方法，生成的SQL語句如下：

Hibernate: insert into t_fiscal_year_period_pk (beginDate, endDate, periodSts, fiscalYear, fiscalPeriod) values (?, ?, ?, ?, ?) 相應(yīng)的數(shù)據(jù)庫視圖：

201677101028658.png (676×95)

3.2 加載操作
相應(yīng)的加載方法會(huì)和以前不同，因?yàn)樵谠摫碇兄麈I是復(fù)合屬性，所以需要?jiǎng)?chuàng)建一個(gè)類。在加載數(shù)據(jù)時(shí)需要?jiǎng)?chuàng)建主鍵對(duì)象，此時(shí)的主鍵就是一個(gè)對(duì)象，更需要為對(duì)象的屬性賦值，這樣才能獲取對(duì)象，代碼如下：

public void testLoad1(){ 
  //聲明會(huì)話對(duì)象 
  Session session=null; 
   
  try{ 
    //獲取會(huì)話對(duì)象 
    session=HibernateUtils.getSession(); 
    //開啟會(huì)話 
    session.beginTransaction(); 
    //創(chuàng)建復(fù)合對(duì)象 
    FiscalYearPeriodPK fiscalyearperiodpk=new FiscalYearPeriodPK(); 
    fiscalyearperiodpk.setFiscalPeriod(2014); 
    fiscalyearperiodpk.setFiscalYear(2012); 
     
    FiscalYearPeriod fiscalyearperiod=(FiscalYearPeriod)session.load(FiscalYearPeriod.class,fiscalyearperiodpk); 
    System.out.println("開始日期： "+fiscalyearperiod.getBeginDate());  
    //提交會(huì)話 
    session.getTransaction().commit(); 
  }catch(Exception e){ 
    e.printStackTrace(); 
    session.getTransaction().rollback(); 
  }finally{ 
    HibernateUtils.closeSession(session); 
  } 
}

生成的結(jié)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=? 
開始日期： 2013-10-12

4、綜合示例
一個(gè)規(guī)模較大公司的部門表(hibernate_dept_compositePK)，由所在區(qū)域(area)，部門名(name)，本部門人數(shù)(empCount),組建時(shí)間(birthday)等字段組成，我們使用所在區(qū)域和部門名做聯(lián)合主鍵：
4.1 目標(biāo)類：Department.java

public class Department { 
 /** 把主鍵關(guān)聯(lián)屬性抽象出來單獨(dú)寫成一個(gè)類 */ 
 //private String area; 
 //private String name; 
 /**把主鍵類對(duì)象作為成員變量*/ 
 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主鍵類：DepartmentPK.java

public class DepartmentPK implements Serializable { 

 private static final long serialVersionUID = -288002855915204255L; 
 private String area; 
 private String name; 
 /** 
  * 覆蓋hashCode方法(根據(jù)area和name判斷) 
  */ 
 //@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; 
 } 
 /** 
  * 覆蓋equals(根據(jù)area和name判斷) 
  */ 
 @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"> 
  <!-- 聯(lián)合主鍵 --> 
  <!-- name指的是主鍵對(duì)象屬性 --> 
  <composite-id name="departmentPK"> 
   <!-- 這里是主鍵關(guān)聯(lián)屬性 --> 
   <key-property name="area" /> 
   <key-property name="name" /> 
  </composite-id> 
  <!-- 其它屬性 --> 
  <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測(cè)試類：DepartmentTest.java

public class DepartmentTest extends TestCase { 
 /** 
  * 測(cè)試插入數(shù)據(jù) 
  */ 
 public void save() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   Department dept = new Department(); 
   /** 生成主鍵對(duì)象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研發(fā)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); 
  } 
 } 
 /** 
  * 測(cè)試加載數(shù)據(jù) 
  */ 
 public void load() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主鍵對(duì)象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研發(fā)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); 
  } 
 } 
  
 /** 
  * 測(cè)試修改數(shù)據(jù) 
  */ 
 public void update() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主鍵對(duì)象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研發(fā)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); 
    
   /** 生成主鍵對(duì)象 */ 
   DepartmentPK deptPK2 = new DepartmentPK(); 
   deptPK2.setArea("北京"); 
   deptPK2.setName("研發(fā)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); 
  } 
 } 
  
 /** 
  * 測(cè)試刪除數(shù)據(jù) 
  */ 
 public void delete() { 
  Session session = HibernateUtils.getSession(); 
  Transaction t = session.beginTransaction(); 
  try { 
   /** 生成主鍵對(duì)象 */ 
   DepartmentPK deptPK = new DepartmentPK(); 
   deptPK.setArea("北京"); 
   deptPK.setName("研發(fā)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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