急！！！如何在jsp中把byte[]转换成image，然后在applet中显示出来？（分数可以再加）__the_file_image_you_String_

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急！！！如何在jsp中把byte[]转换成image，然后在applet中显示出来？（分数可以再加）

来源: 互联网发布时间：2017-04-08

本文导语: 我通过一个c++的exe程序输出一个jpeg图象的流，然后在jsp中取到后转成byte[],怎样在jsp中把byte[]转换成image，然后在applet中通过url调用jsp显示出来？ (c++是完成另一种格式的图象到jpeg的转换) applet代码 import java.applet.*; im...

我通过一个c++的exe程序输出一个jpeg图象的流，然后在jsp中取到后转成byte[],怎样在jsp中把byte[]转换成image，然后在applet中通过url调用jsp显示出来？
(c++是完成另一种格式的图象到jpeg的转换)

applet代码
import java.applet.*;
import java.awt.*;
import java.net.*;
import java.io.*;
import javax.swing.*;

public class export_jpeg extends Applet
{
  Image image;
  URL  iurl = null;
  String status="";
  public void init()
  {
   try{
    iurl=new URL  ("http://zhangxike:8080/clever/multiView/export_jpeg.jsp");

   image = Toolkit.getDefaultToolkit().getImage(iurl);

    }catch (Exception e)
     {
    System.out.println(e.getMessage());
     }

  }

  public void paint(Graphics g)
  {
     g.drawImage(image, 0, 0,this);
//     System.out.println("paint image wrong ....");

  }

}

jsp代码

Image img=this.getToolkit().createImage(byte[],width,height);//用byte[]建立图象
显示的话，直接
g.drawImage(img,0,0,this);
------------
ok????!!!!

you can use Servlet
http://softwaredev.earthweb.com/java/article/0,,12082_1488051_3,00.html
Acquiring a Binary Stream for the Response
Suppose you want to open a binary file in a browser from a servlet. It isn't text so you have to write the file to the servlet's output stream. Let's practice with a PDF document. First, you get the servlet's output stream with:

ServletOutputStream out = res.getOutputStream();
Next, you set the file type in the response object using one of the standard MIME (Multipurpose Internet Mail Extension) protocols. Several listings of content type names are available on the Internet including one at ftp://ftp.isi.edu/in-notes/iana/assignments/media-types. Then you use an HTTP response header named content-disposition. This header allows the servlet to specify information about the file's presentation. Using that header, you can indicate that the content should be opened separately (not actually in the browser) and that it should not be displayed automatically, but rather upon some further action by the user. You can also suggest the filename to be used if the content is to be saved to a file. That filename would be the name of the file that appears in the Save As dialog box. If you don't specify the filename, you are likely to get the name of your servlet in that box. To find out more about the content-disposition header, check out Resources or go to http://www.alternic.org/rfcs/rfc2100/rfc2183.txt.

Sending a binary stream to the client is not easy. Listing 4.10 will help you do it right.

Listing 4.10 Servlet That Sends a File to the Client
public class BinaryResponse extends HttpServlet {

  /**Set global variables*/
  public void init(ServletConfig config)
      throws ServletException
  {
   super.init(config);
  }

  /**Process HTTP Post request with doPost*/
  public void doPost(HttpServletRequest request,
           HttpServletResponse response)
    throws ServletException, IOException
  {

   String fileName = "index.html"; //set file name
   String contentType = getContentType(fileName);
   //contentType = getType(); //get the content type

   // get the file
   File file = new File(fileName);
   long length = file.length();
   if(length > Integer.MAX_VALUE)
   {
     //handle too large file error
     //perhaps log and return error message to client
   }
   byte[] bytes = new byte[(long)length];
   BufferedInputStream in =
    new BufferedInputStream(new FileInputStream(file));
   // then place it into a byte array
   if(length != in.read(bytes))
   {
     //handle too large file error
     //perhaps log and return error message to client
   }

   //get the servlet's output stream
   BufferedOutputStream out =
   new BufferedOutputStream(response.getOutputStream());
   //set the content type of the response
   response.setContentType( contentType );
   //send the file to the client
   out.write( bytes );
  }
}

  /**Clean up resources*/
  public void destroy()
  {
   //If you need to clean up resources.
   //Otherwise don't override.
  }
  String getContentType(String fileName)
  {
   String extension[] =
   {              // File Extensions
     "txt",            //0 - plain text
     "htm",            //1 - hypertext
     "jpg",            //2 - JPEG image
     "gif",            //3 - gif image
     "pdf",            //4 - adobe pdf
     "doc",            //5 - Microsoft Word
   },                // you can add more
   mimeType[] =
   {             // mime types
     "text/plain",         //0 - plain text
     "text/html",         //1 - hypertext
     "image/jpg",         //2 - image
     "image/gif",         //3 - image
     "application/pdf",      //4 - Adobe pdf
     "application/msword",     //5 - Microsoft Word
   },                // you can add more
   contentType = "text/html";    // default type

   // dot + file extension
   int dotPosition = fileName.lastIndexOf('.');
   // get file extension
   String fileExtension =
       fileName.substring(dotPosition + 1);
   // match mime type to extension
   for(int index = 0; index