[TOC]
页面的处理，前面我们已经完成了，现在就要去处理后端了，分页查询，之前我们写了最简单的，不带条件的查询，现在我们需要去修改这个方法，
把前面的 省、市、区、关键字 带上，做模糊查询，在组装查询条件之前，我们判断参数是否为空。现在我们去书写一下。可是问题来了，
我们的 省、市、区 需要查询的是 区域表 而不是 分区表，也就是说，这里涉及到多表查询，应该如何进行查询呢？
hibernate 多表查询，使用的是别名的方式，例如：我们添加 省 这个字段的查询，如下
dc.createAlias("region", "r");
dc.add(Restrictions.like("r.province", "%"+province+"%"));这样，就可以多表查询了。
综合上述，我们的查询方法，就可以如下了：
/**
* 分页查询
* @return
*/
public String pageQuery(){
DetachedCriteria dc = pageBean.getDetachedCriteria();
String addresskey = model.getAddresskey();
//动态添加过滤条件
if(StringUtils.isNotBlank(addresskey)){
//添加过滤条件，根据地址关键字模糊查询
dc.add(Restrictions.like("addresskey","%"+addresskey+"%"));
}
Region region = model.getRegion();
if(region!=null) {
String province = region.getProvince();
String city = region.getCity();
String district = region.getDistrict();
//添加过滤条件，根据省份模糊查询-----多表关联查询，使用别名方式实现
//参数一：分区对象中关联的区域对象属性名称
//参数二：别名，可以任意
dc.createAlias("region","r");
if(StringUtils.isNotBlank(province)){
dc.add(Restrictions.like("r.province", "%"+province+"%"));
}
if(StringUtils.isNotBlank(city)){
dc.add(Restrictions.like("r.city", "%"+city+"%"));
}
if(StringUtils.isNotBlank(district)){
dc.add(Restrictions.like("r.district", "%"+district+"%"));
}
}
subareaService.pageQuery(pageBean);
java2Json(pageBean,new String[]{"currentPage","detachedCriteria","pageSize","subareas"});
return NONE;
}我们之前添加的数据太少了，现在我们添加一些数据
使用一下sql
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj002","QY002","西城区","1","2","0","西城路1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj003","QY003","朝阳区","1","2","0","朝阳区000号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj004","QY004","丰台区","1","2","0","丰台区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj005","QY005","石景山区","1","2","0","石景山区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj006","QY006","海淀区","1","2","0","海淀区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj007","QY007","门头沟区","1","2","0","门头沟区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj008","QY008","房山区","1","2","0","房山区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("bj009","QY009","西城区","1","2","0","西城区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("hb001","QY017","长安区","1","2","0","长安区0002号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("hb002","QY018","桥东区","1","2","0","桥东区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("hb003","QY019","桥西区","1","2","0","桥西区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("tj001","QY041","河东区","1","2","0","河东区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("tj002","QY042","河西区","1","2","0","河西区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("tj003","QY043","南开区","1","2","0","南开区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("sx001","QY056","小店区","1","2","0","小店区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("sx002","QY057","迎泽区","1","2","0","迎泽区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("sx003","QY058","杏花岭区","1","2","0","杏花岭区1001号");
insert into bc_subarea(id,region_id,addresskey,startnum,endnum,single,position) values("sx004","QY059","尖草坪区","1","2","0","尖草坪区1001号");
我们添加了数据，以后来进行查询，如图：
我们发现，界面上仍然没有改变，我们获取到返回的json数据如下
{
"rows": [
[
{
"city": "北京市",
"citycode": "beijing",
"district": "西城区",
"id": "QY002",
"name": "北京市 北京市 西城区",
"postcode": "110102",
"province": "北京市",
"shortcode": "BJBJXC"
},
{
"addresskey": "西城区",
"decidedzone": null,
"endnum": "2",
"id": "bj002",
"position": "西城路1001号",
"region": {
"city": "北京市",
"citycode": "beijing",
"district": "西城区",
"id": "QY002",
"name": "北京市 北京市 西城区",
"postcode": "110102",
"province": "北京市",
"shortcode": "BJBJXC"
},
"single": "0",
"startnum": "1"
}
]
],
"total": 1
}应该放回的一条数据，可是这个返回了两条数据，返回的应该是是分区的数据，可是我们上面看到返回的一条分区数据和一条区域数据。
这个是为什么呢？我们调试看一下，如下图示
我们可以看到，原本1 这个地方，返回的应该是 Subarea 的对象，可是现在返回的是一个数组，这个数据中有两个元素，
一个是 Subarea 和一个 Region。那么这个问题是什么原因引起的？
其实主要就是 2 这个关联查询引起的，那么怎么解决？？
上面说了，是由于 2 那个查询引起的，那么我们现在看看怎么回事。多表查询，默认数据的处理方式是如下图
我们可以看到，它没有把 Region 封装进入 Subarea 中。我们希望的数据是 Region 封装进入 Subarea 中，如下图
那么怎么解决呢？解决方式就是在，我们的分页查询中指定hibernate框架封装对象的方式，其实就是在BaseDao 的分页查询中，加入下面一句话
//指定hibernate框架封装对象的方式
detachedCriteria.setResultTransformer(DetachedCriteria.ROOT_ENTITY);修改以后的BaseDao中的 pageQuery 方法应该如下
/**
* 分页查询
*/
@Override
public void pageQuery(PageBean pageBean) {
int currentPage = pageBean.getCurrentPage();
int pageSize = pageBean.getPageSize();
DetachedCriteria detachedCriteria = pageBean.getDetachedCriteria();
//查询total---总数据量
detachedCriteria.setProjection(Projections.rowCount());
List<Long> countList = (List<Long>) this.getHibernateTemplate().findByCriteria(detachedCriteria);
Long count = countList.get(0);
pageBean.setTotal(count.intValue());
//查询rows---当前页需要展示的数据集合
detachedCriteria.setProjection(null);//指定hibernate框架发出sql的形式----》select * from bc_staff;
//指定hibernate框架封装对象的方式
detachedCriteria.setResultTransformer(DetachedCriteria.ROOT_ENTITY);
int firstResult = (currentPage - 1) * pageSize;
int maxResults = pageSize;
List rows = this.getHibernateTemplate().findByCriteria(detachedCriteria, firstResult, maxResults);
pageBean.setRows(rows);
}这样，我们返回的数据就是对的了，如图：
