（实战）从关联表中取得JSON数据

需求：现有两张表，需要从中取出给前台做级联的JSON格式数据，省份中有城市，城市中有经销商。

一张字典表CMS_DICTIONARY 存放省份信息和城市信息，表结构为：

CID NUMBER(38) 主键   
UPID NUMBER(38) 上级关联外键
CNNAME VARCHAR2(255) 中文名称  

ps：其中UPID=1的为省份

一张经销商表TB_AUDI_DEALER存放经销商相关信息，表结构为：

AID NUMBER(38) 主键   
PROVINCE NUMBER(38) 省份id
CITY NUMBER(38) 城市id
DEALERNAME VARCHAR2(255) 经销商名称
 

对应的bean和映射配置文件：

1、Province

private Long provinceid;
private Long upid;
private String name;
private Set<City> citys = new HashSet<City>();

<hibernate-mapping>
    <class name="com.oemp.audi.user.Province" table="CMS_DICTIONARY"  >
        <id name="provinceid" type="long">
            <column name="CID" precision="38" scale="0" />
          <generator class="sequence">
    <param name="sequence">SEQ_DICTIONARY</param>
   </generator>
        </id>
        <property name="upid" type="long">
            <column name="UPID"/>
        </property>
        <property name="name" type="java.lang.String">
            <column name="CNNAME" length="50" not-null="false" />
        </property>
        <set name="citys" inverse="true" lazy="false">
   <key>
    <column name="UPID" precision="38" scale="0" />
   </key>
   <one-to-many class="com.oemp.audi.user.City" />
  </set>
    </class>
</hibernate-mapping>

2、City

private Long cityid;
private String name;
private Set<Dealer> dealers = new HashSet<Dealer>();

<hibernate-mapping>
    <class name="com.oemp.audi.user.City" table="CMS_DICTIONARY"  >
        <id name="cityid" type="long">
            <column name="CID" precision="38" scale="0" />
          <generator class="sequence">
                <param name="sequence">SEQ_DICTIONARY</param>
            </generator>
        </id>
        <property name="name" type="java.lang.String">
            <column name="CNNAME" length="50" not-null="false" />
        </property>

        <set name="dealers" inverse="true" lazy="false">
            <key>
                <column name="CITY" precision="38" scale="0" />
            </key>
            <one-to-many class="com.oemp.audi.user.Dealer" />
        </set>
    </class>
</hibernate-mapping>

3、Dealer

private Long dealerid;
private String dealername;

<hibernate-mapping>
    <class name="com.oemp.audi.user.Dealer" table="TB_AUDI_DEALER"  >
        <id name="dealerid" type="long">
            <column name="AID" precision="38" scale="0" />
            <generator class="sequence">
                <param name="sequence">SEQ_DICTIONARY</param>
            </generator>
        </id>
        <property name="dealername" type="java.lang.String">
            <column name="DEALERNAME" length="255" not-null="false" />
        </property>
    </class>
</hibernate-mapping>

 struts2 的 action 中 调动方法

public void getJson(){
            List<Province> list = provinceService.getProvinces();//直接查询得到省份
            List<Province> delP = new ArrayList<Province>();//待删除的省份：省份中城市们为空需删除
            for (Province p : list) {//遍历省份
                Set<City> citys = p.getCitys();//得到城市们
                List<City> delC = new ArrayList<City>();//待删除的经销商：城市中经销商们为空需删除
                if(citys != null && !citys.isEmpty()){//判断城市们是否为空
                    for (City c : citys) {//遍历城市
                        Set<Dealer> dealers = c.getDealers();//得到经销商们
                        if(dealers == null || dealers.isEmpty()){//查看经销商们是否为空
                            delC.add(c);//加入待删除的经销商们
                        }
                    }
                    citys.removeAll(delC);//删除经销商们
                }else{
                    delP.add(p);//加入待删除的城市们
                }
            }
            list.removeAll(delP);//删除城市们

            JsonConfig config = new JsonConfig();//json配置
            PropertyFilter proFilter = new PropertyFilter() {//过滤属性
                public boolean apply(Object arg0, String arg1, Object arg2) {
                    if ("upid".equals(name) || "upid" == name) {
                        return true;
                    }
                    return false;
                }
            };
            config.setJsonPropertyFilter(proFilter);//设置过滤属性
            JSONArray json = JSONArray.fromObject(list, config);//生成json对象
            renderText(json.toString());//输出json格式的字符串
    }

 dao 中调用方法：

 

public List<Province> getProvinces() {
        String hql = "from Province p where p.upid = 1 ";
        List<Province> list = new ArrayList<Province>();
        try{
            list = find(hql);
        }catch(Exception e){
            e.printStackTrace();
        }
        return list;
    }