JSON.java

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import java.sql.*;
/**
 * @author theDogKnight
 * @date : 2018.06.30  09:26
 * @email: 1123706238@qq.com
 */
public class DataBaseOperation {
    private static final String DRIVER_NAME = "com.mysql.jdbc.Driver";
    private static final String URL_FORMER = "jdbc:mysql://localhost:3306/";
    public static Connection connection = null;
    public static Statement statement = null;
    /**
     * 连接数据库
     * @param URL_LATTER 数据库的名称
     * @param USER_NAME  用户名
     * @param PASSWORD   用户密码
     */
    public static void setConnection(String URL_LATTER,String USER_NAME,String PASSWORD){
        String url = URL_FORMER + URL_LATTER;
        try {
            Class.forName(DRIVER_NAME);
            //获取数据库连接
            System.out.println("Connecting to a selected database...");
            connection = DriverManager.getConnection(url,USER_NAME,PASSWORD);
            System.out.println("Connected database successfully");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 查找表内字段
     *
     * @param tableName 要操作的表的名称
     * @param valueName 要操作的字段的名称
     */
    public  static JSONArray searchTable(String tableName, String valueName,int limit) throws SQLException {

        JSONArray array = new JSONArray();

        try {
            statement = connection.createStatement();
            String sql = "SELECT " + valueName + " FROM " + tableName;
            System.out.println("reading database...");
            ResultSet resultSet = statement.executeQuery(sql);
            ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
            int columnCount = resultSetMetaData.getColumnCount();
            while (resultSet.next()) {
                JSONObject jsonObject = new JSONObject();
                for (int i = 1; i <= columnCount; i++) {
                    String columnName = resultSetMetaData.getColumnLabel(i);
                    String word_value = resultSet.getString(columnName);
                    jsonObject.put(columnName, word_value);
                }
                array.add(jsonObject);
                System.out.println("read database successfully");

            }
        }catch (SQLException e) {
            e.printStackTrace();
        }
        return array;
    }