看下下面的示例
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;

public class photo extends HttpServlet
{
    Connection conn=null;
    PreparedStatement pstmt=null;
    ResultSet rs=null;   
    public void init(ServletConfig conf) throws ServletException
     {
super.init(conf);

try{
            Class.forName("org.gjt.mm.mysql.Driver");      
   }catch(ClassNotFoundException e){}
String url="jdbc:mysql://localhost:3306/Sample?user=root;password=";
// String user="root",password="";
try{
      conn=DriverManager.getConnection(url);
      pstmt=conn.prepareStatement("select photo from person where id=?");
   }catch(SQLException e){System.err.println("Something is error!");}
     }
    public void doGet(HttpServletRequest request,HttpServletResponse response) 
throws ServletException,IOException
     {
int id=Integer.parseInt(request.getParameter("id"));
int length;
InputStream is=null;
byte[] buffer=new byte[4096];
response.setContentType("images/*");
DataOutputStream os=null;
try{
     pstmt.setInt(1,id);
     rs=pstmt.executeQuery();
     os=new DataOutputStream(response.getOutputStream());
     is=rs.getBinaryStream("photo");
   }catch(SQLException e){} 
while((length=is.read(buffer))!=-1)
   {
      os.write(buffer,0,length);
      os.flush();
   }   
     }
    public void doPost(HttpServletRequest request,HttpServletResponse response) 
throws ServletException,IOException
     {
doGet(request,response);
     }
    public void destroy()
     {
try{
      rs.close();
      pstmt.close();
      conn.close();
           }catch(SQLException e){}
     }
}
在JSP里的调用方式：