create table image 
(id int primary key auto_increment , 
 name varchar(30) COMMENT '名称', 
 content mediumblob COMMENT '图片');

package jdbc_imagetest;

import java.io.*;
import java.sql.*;
/**
 * 将本地文件的图片传到数据库的test的image表中并下载到本机桌面
 */
public class Test1 {

  private static String url="jdbc:mysql://localhost:3306/test";
  private static String user="root";
  private static String password="123456";
  private static Connection con;

  public static void main(String[] args) throws Exception {
    Class.forName("com.mysql.jdbc.Driver");
    con=DriverManager.getConnection(url,user,password);
    shangchuan();
    xiazai();    
  }
  //添加图片到数据库test4的file表
  public static void shangchuan() throws Exception{
    String sql="insert into image(name,content) values(?,?)";
    PreparedStatement ptmt=con.prepareStatement(sql);
    ptmt.setString(1, "美女.jpg");
    InputStream is=null;
    is=new FileInputStream("D:\Pictures\3.jpg");
    ptmt.setBinaryStream(2, is,is.available());
    //方法说明：PreparedStatement.setBinaryStream(int parameterIndex, InputStream x, int length)
    ptmt.execute();
    System.out.println("图片添加成功！");

  }
  //从数据库中把图片下载至桌面
  public static void xiazai() throws Exception{
    String sql="select content from image where id=3";//在我这里3.jpg是第三张图片
    Statement stmt=con.createStatement();
    ResultSet rs=stmt.executeQuery(sql);//将查询结果给rs
    if(rs.next()){
      InputStream is=rs.getBinaryStream("fcontent");
      //.getBinaryStream():a Java input stream that delivers the database column value as a stream of uninterpreted bytes
      FileOutputStream fos=new FileOutputStream("C:\Users\Desktop\美女.jpg");
      byte[] buffer=new byte[1024];
      int len=0;
      while((len=is.read(buffer))!=-1){
        fos.write(buffer,0,len);//将数据库的图片写出
      }
      System.out.println("下载成功！已下载至桌面，请查看");
    }else{
      System.out.println("图片不存在！");
    }
    con.close();
  }


}