HQL的select new map ···语法

通常hibernate查询出的结果集是类似于 List<T> 或 List<Object[]> 的类型

类似于下面这个方法

public List<SfJmsfT> getChosePayList(SfJmsfT jmsf) {
        List list = new ArrayList();
        StringBuilder hql = new StringBuilder();
        hql.append("From SfJmsfT where zf = 0 and yhbh=? and czbh=?");
        List<SfJmsfT> result = null;
        try {
            result = this.executeHqlList(hql.toString(), new Object[]{jmsf.getYhbh(),jmsf.getCzbh()});
        } catch (BDXCException e) {            
            e.printStackTrace();
            logger.error(BDXCUtil.getExceptionString(e));
        }
        return result;
    }

其实hibernate可以查询出List<Map<String,Object>>类型的结果集。现简单代码描述

语句1

// 结果list中，每条记录对应一个object数组，object[]中每个元素为hql语句中列的序号（从0开始）。
 String hql=“select s.name from Student s”;
 List ls=session.createQuery(hql).list();
 for(String obj[]:ls){
       System.out.pringln(obj[0]);
 } 

语句2

//结果list中，每条记录对应一个map，map中key为hql语句中的序号，从0开始，key为字符，非数字。
String hql=“select new map(s.name) from Student s”;
List ls=session.createQuery(hql).list();
for(Map m:ls){
      System.out.pringln(m.get("0"));
}        

语句3

//结果list中，每条记录对应一个map，map中key为hql语句中的别名。
String hql=“select new map(s.name as name)  from Student s”;
List ls=session.createQuery(hql).list();
for(Map m:ls){
       System.out.pringln(m.get("name"));
}        

hibernate对 select new map类型的hql解析的时候，遇到map这个关键字，将后面的列作为值，别名作为键（若无别名，则用数字代替）存入到一个HashMap中。 

方法中使用该类型hql

    public String getThirdPayList(BDXCPageContext context, SfJmsfT queryVo) {

        List list = new ArrayList();
        // 根据queryVo对象转换查询条件
        String sql = "SELECT COUNT(yhbh) FROM sf_jmsf_t WHERE zf='0' and jffs='银行' ";
        sql=sqlPingjie(sql,queryVo);
        Long num = serialBillDao.getThirdPayListCount(sql, list.toArray());
        context.setTotalNum(num.intValue());
        String hql = " select new map(bh as bh,yhbh as yhbh,cnq as cnq,fylb as fylb ,"
                + "jfrq as jfrq,jfje as jfje,zkje as zkje,czbh as czbh,lsh as lsh ,jffs as jffs ,"
                + "czy as czy) FROM SfJmsfT  WHERE zf='0' ";
        hql=sqlPingjie(hql,queryVo);
        List result = serialBillDao.getThirdPayList(hql, list, context);
        String msg = BDXCUtil.createJsonStr(context.getTotalNum(), result);
        return msg;
    
    }

附：select new ***类型解释

select new List(p.name, p.address) from Person as p ;
--select将选择出来的属性存入一个List对象中

select new ClassTest(p.name, p.address) from Person as p;
--select将选择出来的属性封装成对象,前提是ClassTest支持p.name, p.address的构造函数,

select new Map(p.name as personName) from Person as p ;
--select将选中的表达式命名为别名,这种用法与new Map()结合,选择出来的是Map结构, 以personName为key,将实际选择出来的值作为value