Java中的缩略图程序每次刷新页面时都会为图像提供随机图像

Question

I have this java servlet Thumbnail.do which generates a thumbnail image everytime you send a request to it .User has to pass the file name and width the user wants for the image.

The code I am using is below:

public String Image="",ImgWidth="";


Image= "d:\\app\\project\\media\\"+req.getParameter("image");
ImgWidth= req.getParameter("width");
BufferedImage  bufferedimage =ImageIO.read(new File(Image))
float scale=1;
int targetWidth=0;
int targetHeight=0;
Imgwidth=req.getParameter("width");
targetWidth=(int)(bufferedimage.getWidth(null)* scale);
targetHeight=(int)(bufferedimage.getHeight(null)* scale);
if(ImgWitdh == null || ImgWitdh.equlas("")){
ImgWitdh ="0";

}
if(targetWidth>Integer.parseInt(ImgWitdh)&& !ImgWitdh.equals("0")){
targetHeight=Integer.parseInt(ImgWitdh) * targetHeight/targetWidth;
targetWidth=Integer.parseInt(ImgWitdh);
} 

ImageIO.write(createResizedCopy(bufferedimage,targetWidth,
targetHeight,imageOutput,
res.getOutputStream());



 BufferedImage createResizedCopy(Image originalImage, int scaledWidth, int       
 scaledHeight) 
{
 BufferedImage  bufferedimage =new BufferedImage(scaledWidth, scaledHeight,  
 BufferedImage.TYPE_INT_RGB );

 Graphics2D g = scaledBI.createGraphics();
 g.setComposite(AlphaComposite.Src);
 g.drawImage(originalImage,0,0,scaledWidth,scaledHeight,null);
 g.dispose();
}

And on whichever page I have to display the image ,I call the servlet Like this

<img src="../Thumbnail.do?image="the_image_name"&width=150&target="+Math.random()+"/>

till this everything works fine the image are getting converted to the said size and are getting displayed on the page . But the problem is Suppose on the same page I am calling Thumbnail.do multiple times to display different images at various locations on the page like

 <div>
 <img src="../Thumbnail.do?image="emp.png"&width=150&target="+Math.random()+"/>
 </div>
 <div>
 <img src="../Thumbnail.do?image="logo.png"&width=50&target="+Math.random()+"/>
 </div.

then what happens is every time I refresh the page random images are displayed in the div tags. can anyone suggest why and if anyone knows the solution reply

Answer 1

If I understand your question correctly, the problem is the browser caches the image from your servlet. You can disable caching in your servlet code using the approaches described in the link: How to prevent the result of Servlets from being cached