Hibernate Set集合排序

Hibernate Set集合排序

本文探讨对Hibernate的set集合进行排序。假如有两张表：课程信息表(ECH_LEARN_COURSE)和课程分类信息表(ECH_LEARN_COUCATEGORY)，它们之间是一对多的关系。对应的java类分别为EchLearnCourse和EchLearnCoucategory。EchLearnCoucategory有一个Set属性 echLearnCourse,需要对echLearnCourse按课程的排序位置(ORDER_NUM)进行排序。首先使用数据库排序： 
<set name="echLearnCourses" order-by="ORDER_NUM asc" inverse="true" lazy="true"> 
       <cache usage="read-write"/> 
       <key> 
           <column name="CATEGORYID" length="32" not-null="true"/> 
       </key>  
       <one-to-many class="cn.echineseblcu.learning.persistence.EchLearnCourse"  /> 
</set> 

但输出的集合无序，无奈，用内存排序吧 
<set name="echLearnCourses" inverse="true" lazy="true" sort="cn.echineseblcu.learning.persistence.CourseComparator"> 
       <cache usage="read-write" /> 
       <key> 
           <column name="CATEGORYID" length="32" not-null="true"/> 
       </key>  
       <one-to-many class="cn.echineseblcu.learning.persistence.EchLearnCourse"  /> 
</set> 
输出的集合依然无序。没辙了，那就用TreeSet试试： 
即在映射类中定义相应的TreeSet属性echLearnCoursesTreeSet，让EchLearnCoucategory类实现Comparable接口。在EchLearnCoucategory中定义内部类CourseComparator，将EchLearnCourse 按orderNum排序。 
     public TreeSet<EchLearnCourse> getEchLearnCoursesTreeSet() { 
echLearnCoursesTreeSet.addAll(echLearnCourses); 
return echLearnCoursesTreeSet; 
    } 
     public class CourseComparator implements Comparator{ 
    public int compare(Object o1,Object o2){ 
      EchLearnCourse c1=(EchLearnCourse)o1; 
      EchLearnCourse c2=(EchLearnCourse)o2; 
        if(c1.getOrderNum().compareTo(c2.getOrderNum())>0) 
        return 1; 
        if(c1.getOrderNum().compareTo(c2.getOrderNum())<0) 
        return -1; 
        return 0; 
    } 
} 
输出某分类下的课程时使用echLearnCoursesTreeSet，而不用echLearnCourses。 

具体映射文件及java类如下： 
课程信息表映射文件及对应的java类： 
<!--EchLearnCourse.hbm.xml--> 
<hibernate-mapping> 
    <class name="cn.echineseblcu.learning.persistence.EchLearnCourse" table="ECH_LEARN_COURSE" schema="ECHINESE2"> 
        <cache usage="read-write"/> 
        <id name="id" type="java.lang.String"> 
            <column name="ID" length="32" /> 
            <generator class="uuid.hex" /> 
        </id> 
        <many-to-one name="echLearnCoucategory" class="cn.echineseblcu.learning.persistence.EchLearnCoucategory" fetch="select"> 
            <column name="CATEGORYID" length="32" /> 
        </many-to-one> 
        。。。。。。          
    </class> 
</hibernate-mapping> 

<!--EchLearnCourse.java--> 
public class EchLearnCourse extends CommonBean implements java.io.Serializable,Comparable { 
    // Fields    

     public int compareTo(Object o) { 
// TODO Auto-generated method stub 
return 0; 
} 

     private EchLearnCoucategory echLearnCoucategory; 
     。。。。。。     
     // Constructors 

    /** default constructor */ 
    public EchLearnCourse() { 
    } 
    
    public EchLearnCourse(String id) { 
    this.id = id; 
    } 

    。。。。。。 
    public EchLearnCoucategory getEchLearnCoucategory() { 
        return this.echLearnCoucategory; 
    } 
    
    public void setEchLearnCoucategory(EchLearnCoucategory echLearnCoucategory) { 
        this.echLearnCoucategory = echLearnCoucategory; 
    } 

    。。。。。。 
    public boolean equals(Object o) 
    { 
        return EqualsBuilder.reflectionEquals(this, o); 
    } 
    
    public int hashCode() 
    { 
        return HashCodeBuilder.reflectionHashCode(this); 
    } 

} 
课程分类信息表映射文件及对应的java类： 
<!--EchLearnCoucategory.hbm.xml--> 
<hibernate-mapping> 
    <class name="cn.echineseblcu.learning.persistence.EchLearnCoucategory" table="ECH_LEARN_COUCATEGORY" schema="ECHINESE2"> 
        <cache usage="read-write"/> 
        <id name="id" type="java.lang.String"> 
            <column name="ID" length="32" /> 
            <generator class="uuid.hex" /> 
        </id> 
        。。。。。。    //省略若干属性   
        <set name="echLearnCourses" where="delflag='02'" inverse="true" lazy="true"> 
            <cache usage="read-write"/> 
            <key> 
                <column name="CATEGORYID" length="32" not-null="true"/> 
            </key> 
          
            <one-to-many class="cn.echineseblcu.learning.persistence.EchLearnCourse"  /> 
        </set> 

    </class> 
</hibernate-mapping> 

<!--EchLearnCoucategory.java--> 

public class EchLearnCoucategory extends CommonBean implements java.io.Serializable,Comparable { 

// Fields 

public int compareTo(Object o) { 
// TODO Auto-generated method stub 
return 0; 
} 

private Set echLearnCourses = new HashSet(0); 

private TreeSet<EchLearnCourse> echLearnCoursesTreeSet = new TreeSet<EchLearnCourse>(new CourseComparator()); 

private Set echLearnCoucategoryI18ns = new HashSet(0); 

// Constructors 

/** default constructor */ 
public EchLearnCoucategory() { 
} 
         
。。。。。。//省略若干属性的getter和setter方法 

public Set getEchLearnCourses() { 
return this.echLearnCourses; 
} 

public void setEchLearnCourses(Set echLearnCourses) { 
this.echLearnCourses = echLearnCourses; 
} 

public TreeSet<EchLearnCourse> getEchLearnCoursesTreeSet() { 
echLearnCoursesTreeSet.addAll(echLearnCourses); 
return echLearnCoursesTreeSet; 
} 

public void setEchLearnCoursesTreeSet( 
   TreeSet<EchLearnCourse> echLearnCoursesTreeSet) { 
   this.echLearnCoursesTreeSet = echLearnCoursesTreeSet; 
} 

public class CourseComparator implements Comparator{ 
    public int compare(Object o1,Object o2){ 
      EchLearnCourse c1=(EchLearnCourse)o1; 
      EchLearnCourse c2=(EchLearnCourse)o2; 
        if(c1.getOrderNum().compareTo(c2.getOrderNum())>0) 
        return 1; 
        if(c1.getOrderNum().compareTo(c2.getOrderNum())<0) 
        return -1; 
        return 0; 
    } 
} 
}