Java 中操作数据库的工具类

其他文章会用到这个工具类操作数据库，避免写太多代码，直接在这个文章中展示

DBUtil 操作数据库工具类

package com.ssm.util;

import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 数据库工具类
 *
 * @author z
 */
public class DBUtil {

    private String dbname;
    private String user;
    private String password;

    private Connection conn = null;
    private ResultSet rst = null;
    private PreparedStatement pst = null;

    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");    // 5.7
//            Class.forName("com.mysql.cj.jdbc.Driver");  // 8.0
            System.out.println("驱动加载成功！");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public DBUtil(String dbname, String user, String password) {
        this.dbname = dbname;
        this.user = user;
        this.password = password;
    }

    private void getConn() {
        try {
            conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/" + dbname + "?useSSL=false&serverTimezone=UTC&characterEncoding=utf8", user, password);
            System.out.println("链接建立成功！");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    //通过map对象代替我们resultset结果集返回
    // 查询
    public List<Map> query(String sql, Object... obj) {
        getConn();
        try {
            pst = conn.prepareStatement(sql);
            System.out.println(sql);
            for (int i = 0; i < obj.length; i++) {
                System.out.println(obj[i]);
                pst.setObject(i + 1, obj[i]);
            }
            rst = pst.executeQuery();
            // 获取元数据
            ResultSetMetaData metaData = rst.getMetaData();
            List<Map> list = new ArrayList<>();
            while (rst.next()) {
                Map map = new HashMap();
                // 获取查询的元数据的总列数
                int count = metaData.getColumnCount();
                // 列数是从1开始
                for (int i = 1; i <= count; i++) {
                    // 获取当前记录当前索引的列名
                    String key = metaData.getColumnLabel(i);
                    // 获取记录的值
                    Object value = rst.getObject(key);
                    map.put(key, value);
                }
                list.add(map);
            }
            return list;
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
        return null;
    }

    // 增，删，改
    public int update(String sql, Object... obj) {
        int num = 0;
        getConn();
        try {
            pst = conn.prepareStatement(sql);
            System.out.println(sql);
            for (int i = 0; i < obj.length; i++) {
                System.out.println(obj[i]);
                pst.setObject(i + 1, obj[i]);
            }
            num = pst.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
        return num;
    }

    // 关闭流
    public void close() {
        try {
            if (rst != null) {
                rst.close();
            }
            if (pst != null) {
                pst.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}