net.sf.json.JSONObject，将MySQL数据库的数据读出转化为json数据

maven依赖：

    <dependency>
      <groupId>net.sf.json-lib</groupId>
      <artifactId>json-lib</artifactId>
      <version>2.2.3</version>
      <classifier>jdk13</classifier>
    </dependency>

源代码：

package com.reliable.service;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import com.reliable.dao.ReadDB;
import com.reliable.util.JDBCUtil;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;

public class ReadDBImpl implements ReadDB {
    private PreparedStatement preparedStatement=null;
    private Connection conn =null;
    private ResultSet resultSet=null;
    @Override
    public void getAllDbData() throws SQLException {
        HashMap<String, String> map = new HashMap<>();
        ArrayList<String> list = new ArrayList<String>();
        conn= JDBCUtil.getConnection();
        if(conn!=null)
        {
            System.out.println("数据库连接成功！");
        }
        preparedStatement=conn.prepareStatement("select * from hello;");
        resultSet = preparedStatement.executeQuery();
        while(resultSet.next()) {
            String name= resultSet.getString(1);
            String sex =resultSet.getString(2);
            String age= resultSet.getString(3);
            list.add(name+","+sex+" "+age);
        }
        for (int i=0;i<list.size();i++)
        {
            map.put(String.valueOf(i),list.get(i));
        }
        JSONObject jo = JSONObject.fromObject(map);
//        System.out.println(jo);

        //遍历 01
        Set<String> keys = map.keySet();  //map.keySet()返回key的集合
        for(String key:keys) {
            System.out.println(key+":"+map.get(key));  //map.get(key)返回key所对应的value值
        }
        System.out.println("--------------------------");
        //遍历 02
        Iterator<String> it02 = keys.iterator();
        String key;
        while (it02.hasNext()) {
            key = it02.next();
            System.out.println(key+":"+map.get(key));
        }
        System.out.println("--------------------------");
        //遍历 03
        Set<Map.Entry<String,String>> entrySet = map.entrySet();  //map.entrySet()返回<key,value>键值对的集合
        for (Map.Entry<String,String> entry:entrySet) {
            System.out.println(entry.getKey()+":"+entry.getValue());  //entry.getKey()返回key,entry.getValue()返回value
        }
        //遍历 04
        System.out.println("--------------------------");
        Iterator<Map.Entry<String,String>> it04 = entrySet.iterator();
        Map.Entry<String,String> entry;
        while (it04.hasNext()) {
            entry = it04.next();
            System.out.println(entry.getKey()+":"+entry.getValue());
        }
        JDBCUtil.release(conn,preparedStatement);
    }
}

运行结果：