手把手封装数据层之DButil数据库连接的封装

Posted 2020-10-04

最近这段时间一直在用SSM框架做增删改查，突然想把以前还不会用框架的时候，综合百度和各种资料结合API文档抄袭而来的数据层的封装分享给大家。这边先封装一个DButil。

我这个封装就是烂大街的那种，没什么特别。

//DButil.java

package com.yck.database;

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

public class DButil
{
    private static String username;
    private static String password;
    private static String url;
    private static String driver;
    static
    {
        getDatabaseInfo("jdbc.properties");
        try
        {
            Class.forName(driver);
        } catch (ClassNotFoundException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public static void getDatabaseInfo(String path)
    {
        InputStream in = DButil.class.getClassLoader().getResourceAsStream(path);
        Properties p = new Properties();
        try
        {
            p.load(in);
            username = p.getProperty("jdbc.username");
            password = p.getProperty("jdbc.password");
            url = p.getProperty("jdbc.url");
            driver = p.getProperty("jdbc.driver");
        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }
    
    
    public static Connection getConnection()
    {
        Connection conn = null;
        try
        {
            conn = DriverManager.getConnection(url,username,password);
        }catch (SQLException e)
        {
            e.printStackTrace();
        }
        return conn;
    }
    public static void closeConnection(Connection connection)
    {
        try
        {
            if(connection != null)
            {
                connection.close();
                connection = null;
            }
        }  catch (SQLException e)
        {
            e.printStackTrace();
        }
    }
    
    public static PreparedStatement prepareStatement(Connection connection,String sql)
    {
        PreparedStatement preparedStatement = null;
        try
        {    
            preparedStatement = connection.prepareStatement(sql);
        } catch (SQLException e)
        {
            e.printStackTrace();
        }
        return preparedStatement;
    }
    public static void closePreparedStatement(PreparedStatement preparedStatement)
    {
        try
        {
            if(preparedStatement != null)
            {
                preparedStatement.close();
                preparedStatement = null;
            }
        }  catch (SQLException e)
        {
            e.printStackTrace();
        }
    }
    
    public static Statement createStatement(Connection connection)
    {
        Statement statement = null;
        try
        {    
            statement = connection.createStatement();
        } catch (SQLException e)
        {
            e.printStackTrace();
        }
        return statement;
    }
    public static void closeStatement(Statement statement)
    {
        try
        {
            if(statement != null)
            {
                statement.close();
                statement = null;
            }
        }  catch (SQLException e)
        {
            e.printStackTrace();
        }
    }
    public static ResultSet getResultSet(Statement statement,String sql)
    {
        ResultSet resultSet = null;
        try
        {    
            resultSet = statement.executeQuery(sql);
        } catch (SQLException e)
        {
            e.printStackTrace();
        }
        return resultSet;
    }
    public static void closeResultSet(ResultSet resultSet)
    {
        try
        {
            if(resultSet != null)
            {
                resultSet.close();
                resultSet = null;
            }
        }  catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

}

这里是数据库连接需要的jdbc.properties，我们是通过DButil类的读取properties文件的办法来将DButil实例化的。

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&useSSL=true
jdbc.username=root
jdbc.password=8888888

数据库写了个很简单的来测试

CREATE DATABASE test;
USE test;

CREATE TABLE t_user
(
id INT AUTO_INCREMENT NOT NULL,
name VARCHAR(20),
age INT,
PRIMARY KEY(id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8

手动插了两条数据，数据库的内容如下

下面我们来测试一下，新建一个Test类

package com.yck.database;

import java.sql.*;

public class Test
{

    public static void main(String[] args)
    {
        Connection conn = DButil.getConnection();
        Statement stam =DButil.createStatement(conn);
        String sql = "select * from t_user";
        ResultSet rs = null;
        try
        {
            rs = stam.executeQuery(sql);
            while(rs.next())
            {
                System.out.println(rs.getString("name"));
            }
            
        } catch (SQLException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        DButil.closeResultSet(rs);
        DButil.closeStatement(stam);
        DButil.closeResultSet(rs);
    }

}

运行结果如下，说明我们封装的数据库是能够连接上的