JDBC连接数据库

JDBC连接数据库的主要步骤:

1. Class.forName("com.mysql.jdbc.Driver");//反射 类对象 四种

2.获取连接 Connection conn=DriverManager.getConnection(URL,USER,PASSWORD);

3.编写SQL语句并发送 PrepapredStatement pstm=conn.prepareStatement(sql);

4.获得数据库返回结果 (ResultSet rs) 增删改(int)

5.关闭资源 public static void closeResource(Connection conn,PreparedStatement pstm,ResultSet rs)

接下来我们开始编写JDBC程序代码,实现CLOB类型数据的读写操作,在完成此任务之前,

先将JDBC连接数据库以及关闭数据库代码编写一个MySQLConnectionUtil.java类中,该类的代码如下所示:

 

1.工具类 方法:封装,设置为静态方法,好处,调用方便.

package com.guigu.jdbc;

import java.sql.*;

public class MySQLConnectionUtil {
    private static String DRIVER="com.mysql.jdbc.Driver";
    private static String URL="jdbc:mysql://127.0.0.1:3306/lob";
    private static String USERNAME="root";
    private static String PASSWORD="123456";

    public static Connection getConnection(){
        Connection connection=null;
        try {
            Class.forName(DRIVER);
            connection= DriverManager.getConnection(URL,USERNAME,PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    public static void close(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet){

            try {
                if(resultSet!=null){
                resultSet.close();
                }
                if (preparedStatement!=null){
                    preparedStatement.close();
                }
                if (connection!=null){
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }

    }
}

package com.guigu.jdbc;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class JDBCMySQLCOLBWriter {
    public static void main(String[] args) {
        String sql="INSERT INTO TEXTCLOB VALUES (?,?,?)";
        Connection connection=MySQLConnectionUtil.getConnection();
        PreparedStatement preparedStatement=null;
        try {
             preparedStatement=connection.prepareStatement(sql);
             File file =new File("D:/workspace/site.txt");
             //使用输入流读写文本文件
            InputStream inputStream=new FileInputStream(file);
            //加载SQL语句中VALUES占位符参数
            preparedStatement.setInt(1,1);
            preparedStatement.setString(2,"site.txt");
            preparedStatement.setAsciiStream(3,inputStream);
            int count = preparedStatement.executeUpdate();
            if(count>0){
                System.out.println("数据插入成功");
            }else{
                System.out.println("数据插入失败");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }finally {
            MySQLConnectionUtil.close(connection,preparedStatement,null);
        }
    }
}

上面的示例中,我们需要将文本文件以文件流的方式写入MySQL数据库指定的字段是时,需要使用PreparedStatement对象调用其setAsciiStream()为存储文本文件加载数据.