Java笔记JDBC-MySQL存取图片

一.简述

    通过Java实现将图片存入MySQL数据库，并将其读取出来。需要用到字节流处理图片和JDBC连接数据库。

二.编程步骤

1. 创建一张数据表用于存放数据库，这里我的数据库名为my_image_db，表名为photo，元素分为id (int),name(varchar),photo(blob)。这个表自行创建
2. 通过JDBC连接MySQL数据库
3. 封装读取图片的流
4. 将图片插入数据库
5. 将图片读取出来存入文件夹中

三.简单实例

代码中的图片路径，以及sql语句需根据你的实际情况更改

public class Main_10_20 {
    public static void main(String[] args) throws Exception{
        //System.out.println("开始！");
        //ImageDemo.readImage2DB();//将图片插入数据库
        //ImageDemo.readDB2Image();//读取图片
    }
}

连接数据库

import java.sql.SQLException;
import java.sql.DriverManager;
import java.sql.Connection;

public class DBUtil {
    public static final String Driver_Name="com.mysql.cj.jdbc.Driver";
    public static final String URL = "jdbc:mysql://localhost:3306/my_image_db";//端口用于区分应用,3306是mysql的端口
    public static final String USER = "root";
    public static final String PASSWORD = "***";//连接数据库的密码

    static {  //静态块
        try {
            Class.forName(Driver_Name);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConn() throws SQLException{
        Connection conn = DriverManager.getConnection(URL,USER,PASSWORD);
        return conn;
    }

    public static void closeConn(Connection conn){
        if(null!=conn){
            try{
                conn.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
    }

}

封装读取图片的流

import java.io.*;

public class ImageUtil {
    // 读取本地图片获取输入流
    public static FileInputStream readImage(String path) throws IOException {
        return new FileInputStream(new File(path));
    }

    // 读取表中图片获取输出流
    public static void readBin2Image(InputStream in, String targetPath) {
        File file = new File(targetPath);
        String path = targetPath.substring(0, targetPath.lastIndexOf("/"));
        if (!file.exists()) {
            new File(path).mkdir();
        }
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
            int len = 0;
            byte[] buf = new byte[1024];
            while ((len = in.read(buf)) != -1) {
                //System.out.println(len);
                fos.write(buf, 0, len);
            }
            fos.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (null != fos) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

实现图片的插入以及读取

import java.sql.*;
import java.io.*;

public class ImageDemo {
    // 将图片插入数据库
    public static void readImage2DB() {
        System.out.println("将图片插入数据库");
        String path = "/Users/huangjw/Documents/read.jpg";//这里根据实际情况更改
        Connection conn = null;
        PreparedStatement ps = null;
        FileInputStream in = null;
        try {
            in = ImageUtil.readImage(path);
            conn = DBUtil.getConn();
            String sql = "insert into photo (id,name,photo)values(?,?,?)";
            ps = conn.prepareStatement(sql);//这里根据实际情况更改
            ps.setInt(1, 1);
            ps.setString(2, "Tom");
            System.out.println(in.available());
            ps.setBinaryStream(3, in, in.available());
            int count = ps.executeUpdate();//执行sql
            if (count > 0) {
                System.out.println("插入成功！");
            } else {
                System.out.println("插入失败！");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.closeConn(conn);
            if (null != ps) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    // 读取数据库中图片
    public static void readDB2Image() {//这里根据实际情况更改
        String targetPath = "/Users/huangjw/Desktop/other/read.jpg";//读取后存放图片的路径
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = DBUtil.getConn();
            String sql = "select * from photo where id =?";
            ps = conn.prepareStatement(sql);//这里根据实际情况更改
            ps.setInt(1, 1);
            rs = ps.executeQuery();
            while (rs.next()) {
                InputStream in = rs.getBinaryStream("photo");
                ImageUtil.readBin2Image(in, targetPath);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.closeConn(conn);
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (ps != null) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

        }
    }
}