Hibernate集合排序之内存排序

使用sort属性，我们可以通过在取回结果集后在内存中进行排序，然后返回一个经过排序的结果集合

数据库结构：

create table teamSort (id varchar(32),teamname varchar(32));

create table studentSort (name varchar(32),team_id varchar(32));

insert into teamSort values("1","team1");

insert into studentSort values("a","1");

insert into studentSort values("b","1");

insert into studentSort values("c","1");

pojo: student部分采用set集合，无实体类

package Collection.Sort;

import java.util.Set;

public class Team {

private String id;

private String teamname;

private Set students;

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

public String getTeamname() {

return teamname;

}

public void setTeamname(String teamname) {

this.teamname = teamname;

}

public Set getStudents() {

return students;

}

public void setStudents(Set students) {

this.students = students;

}

Team.hbm.xml

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping>

</id>

</set>

</class>

</hibernate-mapping>

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">

<hibernate-configuration>

<session-factory>

jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312&useUnicode=true

</property>

org.hibernate.dialect.MySQLDialect

</property>

<property name="myeclipse.connection.profile">mysql</property>

com.mysql.jdbc.Driver

</property>

org.hibernate.dialect.MySQLDialect

</property>

<property name="current_session_context_class">thread</property>

</session-factory>

</hibernate-configuration>

测试代码：

package Collection.Sort;

import java.io.File;

import java.util.Iterator;

import java.util.Set;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

public class Test {

public static void main(String[] args) {

String filePath=System.getProperty("user.dir")+File.separator+"src/Collection/Sort"+File.separator+"hibernate.cfg.xml";

File file=new File(filePath);

System.out.println(filePath);

SessionFactory sessionFactory=new Configuration().configure(file).buildSessionFactory();

Session session=sessionFactory.openSession();

Transaction t=session.beginTransaction();

Team team=(Team)session.createQuery("from Team t where t.teamname='team1'").uniqueResult();

Set result=team.getStudents();

Iterator iter=result.iterator();

while(iter.hasNext()){

System.out.println(iter.next());

}

t.commit();

}

运行结果：

Hibernate: select team0_.id as id0_, team0_.teamname as teamname0_ from teamSort team0_ where team0_.teamname='team1'
Hibernate: select students0_.team_id as team1_0_, students0_.name as name0_ from studentSort students0_ where students0_.team_id=?
a
b
c

sort="natural"默认进行升序排列，如果我们想改成降序，则需要写一个类实现Comparator接口如下：

package Collection.Sort;

import java.util.Comparator;

public class Compare implements Comparator {

public int compare(Object o1, Object o2) {

String s1=(String)o1;

String s2=(String)o2;

if(s1.equals(s2)){

return 0;

}

else if(s1.compareTo(s2)>0){

return -1;

}

else{

return 1;

}

然后更改Team.hbm.xml 配置sort属性

sort="Collection.Sort.Compare"

重新执行测试代码，结果如下：

注意：如果有Student实体类，并set中使用one-to-many或many-to-many标签，则比如使用sort="一个实现comparator接口的类"这样排序