JDBC——DBUtil類

在看視頻學習過程中，看到有老師自己封裝的數據庫工具類，感覺用起來很方便；自己也跟着寫了一個，以後再使用JDBC時可直接使用。

import java.sql.*;

/**
 * JDBC的工具類
 */

public class DBUtil {

    private static Connection conn = null;
    private static PreparedStatement pstmt = null;
    private static ResultSet rs = null;
    private DBUtil(){
    }
    
    /**
     * 創建一個連接
     */
    public static Connection getConnection() {
        String url = "jdbc:mysql:// localhost:3306/test?serverTimezone=GMT%2B8";
        try {
            //加載驅動
            Class.forName("com.mysql.cj.jdbc.Driver");
            //建立連接
            conn = DriverManager.getConnection(url, "root", "123456");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 關閉數據庫資源
     */
    public static void closeAll() {
        try {
            if (rs != null) {
                rs.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (pstmt != null) {
                pstmt.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 執行insert、update、delelte 三個DML操作
     * 傳入參數sql語句，以及sql語句中佔位符對應的數據
     */
    public  static int executeUpdate(String sql, Object[] prams){
        conn = getConnection();
        int n = 0;
        try {
            pstmt = conn.prepareStatement(sql);
            for (int i=0;i<prams.length;i++){
                pstmt.setObject(i+1,prams[i]);
            }
            n=pstmt.executeUpdate();
        }catch (SQLException e){
            e.printStackTrace();
        }
        return n;
    }

    /**
     * 執行查詢所返回的Resultset對象
     */
    public static ResultSet executeQuery(String sql, Object[] prams){
        conn = getConnection();
        try {
            pstmt = conn.prepareStatement(sql);
            for (int i=0;i<prams.length;i++){
                pstmt.setObject(i+1,prams[i]);
            }
            rs = pstmt.executeQuery();
        }catch (Exception e){
            e.printStackTrace();
        }
        return rs;
    }
}

增加數據操作：

public int addUser(String uname, String pwd) {
        String sql = "insert into t_user values(default,?,?)";
        Object[] prams = {uname, pwd};
        int ok = DBUtil.executeUpdate(sql, prams);
        DBUtil.closeAll();
        return ok;
    }

刪除數據操作:

String sql = "delete from t_user where uid=?";
Object[] prams = {4};
int ok = DBUtil.executeUpdate(sql, prams);
DBUtil.closeAll();

更新數據操作：

String sql = "update t_user set pwd=? where uname=?";
String uname = "lisi";
String pwd = "789";
Object[] prams = {pwd, uname};
int ok = DBUtil.executeUpdate(sql, prams);
DBUtil.closeAll();

查詢數據操作：

public User login(String uname, String pwd) {
        String sql = "select * from t_user where uname=? and pwd=?";
        Object[] prams = {uname, pwd};

        ResultSet rs = DBUtil.executeQuery(sql, prams);
        User user = null;
        try {
            while (rs.next()) {
                int uid = rs.getInt("uid");
                String name = rs.getString("uname");
                String pwd2 = rs.getString("pwd");
                user = new User(uid, name, pwd2);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        DBUtil.closeAll();
        return user;
    }