JDBC——DBHelper代码模版

JDBC数据库操作代码模版

package com.oolong.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class DBHelper {

    private String driverName = "com.mysql.jdbc.Driver";
    private String url = "jdbc:mysql://localhost:3306/hrms?useSSL=true";
    private String userName = "root";
    private String password = "1234";
    private Connection conn;
    
    private static DBHelper dbHelper;
    
    public static Connection getConnection(){
        if (dbHelper == null) {
            DBHelper.dbHelper = new DBHelper();
        }
        return dbHelper.conn;
    }
    
    private DBHelper() {
        try {
            Class.forName(driverName);
            this.conn = DriverManager.getConnection(url, userName, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public static int executeUpdate(String sql, String[] param) {
        Connection conn = null;
        PreparedStatement pst = null;
        int res = 0;
        
        try{
            conn = DBHelper.getConnection();
            pst = conn.prepareStatement(sql);
            
            for (int i = 0; i < param.length; i++) {
                pst.setString(i+1, param[i]);
            }
            
            res = pst.executeUpdate();
            
            pst.close();
            conn.close();
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return res;
    }
    
    public static List<Map<String, Object>> executeQuery(String sql) {
        return executeQuery(sql, new String[0]);
    }
    
    public static List<Map<String, Object>> executeQuery(String sql, String[] param) {
        Connection conn = null;
        PreparedStatement pst = null;
        ResultSet rs = null;
        List<Map<String, Object>> resut = new ArrayList<>();
        Map<String, Object> map = null;
        try{
            conn = DBHelper.getConnection();
            pst = conn.prepareStatement(sql);
            
            for (int i = 0; i < param.length; i++) {
                pst.setString(i+1, param[i]);
            }
            
            rs = pst.executeQuery();
            
            ResultSetMetaData rsm = rs.getMetaData();
            String[] columns = new String[rsm.getColumnCount()];
            
            for (int i = 0; i < rsm.getColumnCount(); i++) {
                columns[i] = rsm.getColumnName(i + 1);
            }
            
            rs.beforeFirst();
            
            while(rs.next()) {
                map = new HashMap<>();
                for(String col : columns) {
                    map.put(col, rs.getObject(col));
                }
                resut.add(map);
            }
            rs.close();
            pst.close();
            conn.close();
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resut;
    }
}