使用Java从SQL结果集正确创建JSON

我有一张桌子

Country       State

 USA           Texas
 USA           Alasca
 India         Delhi
 India         Bombay
 India         Madras
 Russia        Mosco
 Russia        Petersberg
 Germany       Berlin
 China         Beijing
 China         Tibet
 Turkey        Antioch

我需要在两个选择框中显示这些项目， 国家和州。当从国家选择框中选择美国时，德克萨斯州和阿拉斯加州应显示在州选择框中。 所以我需要创建一个Json对象作为

 [{Country:USA, State:{{statename:Texas},{statename:Alasca}}},
 {Country:India, State:{{statename:Delhi}, {statename:Bombay}, {statename:Madras}}},
  {Country:Germany, State:{{statename:Berlin}},
{Country:Russia, State:{{statename:Mosco},{statename:Petersberg}}},
{Country:China, State:{{statename:Beijing}, {statename:Tibet}}},
 {Country:turkey, State:{{statename:Antioch}}}
 ]

目前，我使用两个单独的sql分别获取country和state。我使用Java类 国家作为

public class Country implements Serializable {

String country;



public String getCountry() {
    return country;
}


public void setCountry(String country) {
    this.country = country;
}

 }

我用刀作为工具

  public List<Country>  extractData(ResultSet rs) throws SQLException,
        DataAccessException {
    List<Country> list = new ArrayList<Country>();

    while (rs.next()) {
        Country obj = new Country();
        obj.setCountry(rs.getString(1).trim());

        list.add(obj);
    }

    return list;
   }

同样，我为state创建了类，并编写了提取数据的代码，得到的状态如下

         [ {state:Texas} {state:Alasca}, {state:Delhi}, {state:Bombay},     {state:Madras}, {state:Berlin}, {state:Mosco}, {state:Petersberg} {state:Beijing}, {state:Tibet}, {state:Antioch}]

这可以单独显示在选择框中

但是我需要用下面的方式将对象正确地显示在选择框中

  [{Country:USA, State:{{statename:Texas},{statename:Alasca}}},
 {Country:India, State:{{statename:Delhi}, {statename:Bombay}, {statename:Madras}}},
  {Country:Germany, State:{{statename:Berlin}},
{Country:Russia, State:{{statename:Mosco},{statename:Petersberg}}},
{Country:China, State:{{statename:Beijing}, {statename:Tibet}}},
 {Country:turkey, State:{{statename:Antioch}}}
 ]

我可以创建一个java类

 class CountryState{
    string country;
    List <State> state;

    public String getCountry()
    {
        return country;
    }

    public void setCountry(String country){
        this.country=country;
    }

    public List<State> getState(){
        return state;
    }

    public void setState(List<State> state)
    {
     this.state.add(state);
     }
    }

    class State{
    String statename;

    public String getStatename()
    {
    return statename;
    }

    public void setStatename(String statename){
    this.statename=statename;
    }

---

我需要知道如何将结果集中的值存储到这样一个对象，并生成所需的JSON对象。

为来自数据库的数据对象创建JAVA pojo，并在该pojo上使用JSON转换器库，就像使用GSON或Jackson一样

提示：您可能必须将查询更改为“按国家分组”，并且可能需要映射到一个国家的状态集合

 class CountryState{
    string country;
    List <State> state;

    public String getCountry()
    {
        return country;
    }

    public void setCountry(String country){
        this.country=country;
    }

    public List<State> getState(){
        return state;
    }

    public void setState(List<State> state)
    {
     this.state.add(state);
     }
    }

    class State{
    String statename;

    public String getStatename()
    {
    return statename;
    }

    public void setStatename(String statename){
    this.statename=statename;
    }