Question

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

 [{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sqls来分别获取国家和州。我使用Java类国家/地区

public class Country implements Serializable {

String country;



public String getCountry() {
    return country;
}


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

 }

我使用DAO作为

  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;
   }

我得到的对象为：

[{country:USA}, {country:India}, {country:Germany}, {country:Russia}, {country:China}, {country:turkey}]

以同样的方式，我创建了用于提取数据的状态和代码的类，我将状态设为

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

这可以分别在选择框中显示。

但我需要以下列方式将对象正确显示在选择框中。

  [{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的对象中并生成所需的JSON对象。

Answer 1

在JAVA中为来自数据库的数据对象创建一个pojo，并在该pojo上使用JSON转换库，就像使用GSON或Jackson一样。

提示：您可能需要将您的查询更改为按国家/地区分组，并且您可能需要映射到一个国家/地区的状态集合。

使用Java从SQL Resultset正确创建JSON

1 个答案: