操作数据库的公共类

java操作数据库的公共类

package com.lzcu.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * Created by wangshilin on 2020/2/11
 * 操作数据库的公共类
 */

public class BaseDao {
    
    
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块，类加载的时候就初始化了
    static {
    
    
        Properties properties = new Properties();
        //通过类加载器读取对应的资源
        InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        try {
    
    
            properties.load(is);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("username");
        password = properties.getProperty("password");

    }

    //获取数据库得连接
    public static Connection getConnection(){
    
    
        Connection connection = null;
        try {
    
    
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }

        return connection;
    }
    
    //编写查询公共类
    public static ResultSet execute(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException {
    
    
        //预编译的SQL在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);

        for (int i = 0 ; i < params.length ; i++) {
    
    
            //setObject,占位符从1开始，但是我们的数组是从0开始
            preparedStatement.setObject(i+1, params[i]);
        }
        resultSet = preparedStatement.executeQuery();

        return resultSet;

    }

    //编写增删改公共方法
    public static int execute(Connection connection,PreparedStatement preparedStatement,
                              String sql,Object[] params) throws SQLException {
    
    
        //预编译的SQL在后面直接执行就可以了
        preparedStatement = connection.prepareStatement(sql);

        for (int i = 0 ; i <params.length ; i++) {
    
    
            //setObject,占位符从1开始，但是我们的数组是从0开始
            preparedStatement.setObject(i+1,params[i]);
        }
        int updateRows = preparedStatement.executeUpdate();

        return updateRows;
    }

    //释放资源，关闭连接
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,
                                        ResultSet resultSet){
    
    
        boolean flag = true;
        if (resultSet!=null){
    
    
            try {
    
    
                resultSet.close();
                //GC回收
                resultSet = null;
            } catch (SQLException e) {
    
    
                e.printStackTrace();
                flag = false;
            }
        }
        if (preparedStatement!=null){
    
    
            try {
    
    
                preparedStatement.close();
                //GC回收
                preparedStatement = null;
            } catch (SQLException e) {
    
    
                e.printStackTrace();
                flag = false;
            }
        }
        if (connection!=null){
    
    
            try {
    
    
                connection.close();
                //GC回收
                connection = null;
            } catch (SQLException e) {
    
    
                e.printStackTrace();
                flag = false;
            }
        }
        return flag;
    }

}

db.properties配置文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=wsl123