hibernate配置文件中的properties元素

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http://huihai.iteye.com/blog/1149635

假如现在有班级Class类与学生student类，但是在映射时，学生表关联的外键不是班级表的主键id，而是年级(grade)与班号(numb)这两个联合作外键，这样就要用到hibernate里的properties属性了。

Class.java类如下：

package cn.ehoo.hibernate.domain;   /**   *@author whp   *@Email whp@ehoo.cn   *@Aug 15, 2011   *   */  public class Class {       private Long id;       private String grade;       private String number;       public String getGrade() {           return grade;       }       public void setGrade(String grade) {           this.grade = grade;       }       public String getNumber() {           return number;       }       public void setNumber(String number) {           this.number = number;       }       public Long getId() {           return id;       }       public void setId(Long id) {           this.id = id;       }                 }

Class.hbm.xml文件如下：

<?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 package="cn.ehoo.hibernate.domain">      <class name="Class" table="class">          <id name="id" type="long">              <generator class="native" />          </id>          <properties name="name" unique="true" update="false">              <property name="grade" />              <property name="number" />          </properties>        </class>  </hibernate-mapping>

Student.java类如下：

package cn.ehoo.hibernate.domain;   /**   *@author whp   *@Email whp@ehoo.cn   *@Aug 15, 2011   *   */  public class Student {       private Long id;       private String name;       private Class cla;       public Class getCla() {           return cla;       }       public void setCla(Class cla) {           this.cla = cla;       }       public Long getId() {           return id;       }       public void setId(Long id) {           this.id = id;       }       public String getName() {           return name;       }       public void setName(String name) {           this.name = name;       }          }

Student.hbm.xml文件如下：

<?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 package="cn.ehoo.hibernate.domain">      <class name="Student" table="student">          <id name="id" type="long">              <generator class="native" />          </id>          <many-to-one name="cla" class="Class" property-ref="name">              <column name="grade"></column>              <column name="number"></column>          </many-to-one>      </class>  </hibernate-mapping>

总之一句话，当你在做关联时，两个表之间的外键关联由两个或以上的属性组成时，就需要用到 properties元素。

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