使用Servlet显示Blob字段中的图像

Question

i created a jsp page that calls another jsp page that show an image took from a blob field in my mysql db:

<img src="blob.jsp"> 

it works. But, somewhere in this forum i read that this is not the right way to do it. I should, instead, using a servlet this way:

 <img src="servlet_name">

I created a servlet, but it doesent show me the image it shows me this

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This is my simple servlet

package Jeans;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.sql.Blob;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/BlobDisplay")
public class BlobDisplay extends HttpServlet {
    private static final long serialVersionUID = 1L;
    GestioneDB gestioneDB ;


    public BlobDisplay() {
        super();       
    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException 
            {       
        Blob image = null;
        byte[ ] imgData = null ;
        String query = null;
        query = request.getParameter(query);        

        gestioneDB = new GestioneDB();

        ResultSet rs =  gestioneDB.rs("select immagine_principale from news where id ='217'");

            try{
            if (rs.next()) {
            image = rs.getBlob("immagine_principale");
            imgData = image.getBytes(1,(int)image.length());

            response.setContentType("image/jpg");
            OutputStream o = response.getOutputStream();
            o.write(imgData);
            o.flush();
            o.close();
            }
        }
        catch(Exception e){}    
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  

         this.doGet(request,response);
    }

}

Answer 1

Here is a debugging hint for now.

JSPs are just "inside out" servlets and they are translated to servlets by the container. Since your JSP works and your servlet doesn't, why don't you check out (and post) the generated servlet. If you are using tomcat, it would be in a file called blob__jsp.java deep in the work directory . Then compare the calls and set up of your servlet and the generated servlet.

(My first guess is the content type, but you seem to be setting that)