java 此类旨在将作为Db查询结果获取的ResultSet数据转换为JSON。还可以使用其他转换器方法

Posted 2021-05-08

import org.json.JSONArray;
import org.json.JSONObject;

import java.sql.ResultSet;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.Locale;

/**
 * Utility for converting ResultSets into some Output formats
 */
public class Convertor {

    /**
     * Convert a result set into a JSON Array
     * @param resultSet
     * @return a JSONArray
     * @throws Exception
     */
    public static JSONArray convertResultSetIntoJSON(ResultSet resultSet) throws Exception {
        JSONArray jsonArray = new JSONArray();
        while (resultSet.next()) {
            int total_rows = resultSet.getMetaData().getColumnCount();
            JSONObject obj = new JSONObject();
            for (int i = 0; i < total_rows; i++) {
                String columnName = resultSet.getMetaData().getColumnLabel(i + 1).toLowerCase();
                Object columnValue = resultSet.getObject(i + 1);
                // if value in DB is null, then we set it to default value
                if (columnValue == null){
                    columnValue = "null";
                }
                /*
                Next if block is a hack. In case when in db we have values like price and price1 there's a bug in jdbc - 
                both this names are getting stored as price in ResulSet. Therefore when we store second column value,
                we overwrite original value of price. To avoid that, i simply add 1 to be consistent with DB.
                 */
                if (obj.has(columnName)){
                    columnName += "1";
                }
                obj.put(columnName, columnValue);
            }
            jsonArray.put(obj);
        }
        return jsonArray;
    }

    public static int converBooleanIntoInt(boolean bool){
        if (bool) return 1;
        else return 0;
    }

    public static int convertBooleanStringIntoInt(String bool){
        if (bool.equals("false")) return 0;
        else if (bool.equals("true")) return 1;
        else {
            throw new IllegalArgumentException("wrong value is passed to the method. Value is "+bool);
        }
    }

    public static double getDoubleOutOfString(String value, String format, Locale locale){
        DecimalFormatSymbols otherSymbols = new DecimalFormatSymbols(locale);
        otherSymbols.setDecimalSeparator('.');
        DecimalFormat f = new DecimalFormat(format,otherSymbols);
        String formattedValue = f.format(Double.parseDouble(value));
        double number = Double.parseDouble(formattedValue);
        return  Math.round(number * 100.0) / 100.0;
    }

}