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

2019-11-26 14:05:38

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復合主鍵映射需要在映射配置文件中使用<composite-id>標簽，該標簽是指將一個類指定為相應的復合主鍵，它的name屬性需要指定類文件中定義的屬性值，并在該標簽中添加<key-property>子標簽。
Note：想要使用復合映射必須要將復合主鍵放到一個類中，也就是講復合主鍵屬性和其它屬性分到兩個類中，并將復合主鍵的類實現(xiàn)接口Serializable，該接口隸屬于java.io。
復合主鍵的映射關系的主鍵是由多個列復合而成的，對應到數(shù)據(jù)表中相當?shù)暮唵危缦聢D：

201677100922504.png (572×73)

1、類文件
這里就拿上圖的表來作為示例，在表中有兩個字段年限和持續(xù)時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的映射，如下代碼：

package com.src.hibernate;  import java.sql.Date;  public class FiscalYearPeriod {      //時間主鍵   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;   }      //結束日期   private Date endDate;   public Date getEndDate() {     return endDate;   }   public void setEndDate(Date endDate) {     this.endDate = endDate;   }      //階段時間   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，并且需要實現(xiàn)接口Serializable，該類是要映射到配置文件中<composite-id>標簽中要指定該類，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
這里有個疑問兩個類都是哪個需要添加映射文件？因為會使用<composite-id>標簽，所以只需要為FiscalYearPeriod類添加映射即可，在該映射文件中添加對應復合主鍵標簽，并在標簽中添加對應的主鍵屬性，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應的數(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))

對應的表結構如下圖：

201677101003756.png (677×190)

3、數(shù)據(jù)操作
相應的映射文件配置好后，相應的數(shù)據(jù)操作就變得很簡單了，首先從寫入數(shù)據(jù)開始，向數(shù)據(jù)庫中寫入數(shù)據(jù)時會同時把兩個類寫入到數(shù)據(jù)庫中，所以此時這兩個類都必須轉化為Transient狀態(tài)，所以在保存時需要首先將FiscalYearPeriod對象首先保存到數(shù)據(jù)庫中，然后它會自動關聯(lián)復合屬性，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，需要定義兩個對象，然后保存相應的對象信息到數(shù)據(jù)庫中，代碼如下：

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

執(zhí)行相應的測試方法，生成的SQL語句如下：

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

201677101028658.png (676×95)

3.2 加載操作
相應的加載方法會和以前不同，因為在該表中主鍵是復合屬性，所以需要創(chuàng)建一個類。在加載數(shù)據(jù)時需要創(chuàng)建主鍵對象，此時的主鍵就是一個對象，更需要為對象的屬性賦值，這樣才能獲取對象，代碼如下：

public void testLoad1(){   //聲明會話對象   Session session=null;      try{     //獲取會話對象     session=HibernateUtils.getSession();     //開啟會話     session.beginTransaction();     //創(chuàng)建復合對象     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());      //提交會話     session.getTransaction().commit();   }catch(Exception e){     e.printStackTrace();     session.getTransaction().rollback();   }finally{     HibernateUtils.closeSession(session);   } }

生成的結果，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 目標類：Department.java

public class Department {  /** 把主鍵關聯(lián)屬性抽象出來單獨寫成一個類 */  //private String area;  //private String name;  /**把主鍵類對象作為成員變量*/  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指的是主鍵對象屬性 -->   <composite-id name="departmentPK">    <!-- 這里是主鍵關聯(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測試類：DepartmentTest.java

public class DepartmentTest extends TestCase {  /**   * 測試插入數(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);   }  }  /**   * 測試加載數(shù)據(jù)   */  public void load() {   Session session = HibernateUtils.getSession();   Transaction t = session.beginTransaction();   try {    /** 生成主鍵對象 */    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);   }  }    /**   * 測試修改數(shù)據(jù)   */  public void update() {   Session session = HibernateUtils.getSession();   Transaction t = session.beginTransaction();   try {    /** 生成主鍵對象 */    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);   }  }    /**   * 測試刪除數(shù)據(jù)   */  public void delete() {   Session session = HibernateUtils.getSession();   Transaction t = session.beginTransaction();   try {    /** 生成主鍵對象 */    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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