flushing image bytes to client browser

[Bharat Makwana]

Hi All,

I am facing some problem with my servlet code, I am trying to display the image returned by 3rd party server in the browser.
But it gives me error : The image “http://localhost:8080/velocity/googlechart/” cannot be displayed, because it contains errors.

code is as follows, can someone tell me what I'm doing wrong here ?

in the code,

String urlStr = "http://chart.apis.google.com/chart?cht=lc&chs=300x250&chxt=x%2Cy&chxs=$&chxl=0%3A|1%20amn|2%20am|3%20am|4%20am|5%20am&chdlp=bv&chco=ff7f00%2C339999%2Ccc9966&chxr=1%2C59%2C1170&chd=t:40,20,50,20,100|75,74,66,30,10";

is the .png image url.

  
public class HTTPConnection extends HttpServlet{
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
			byte [] data = getData();
			resp.setContentType("image/PNG");
			resp.getOutputStream().write(data);
	}
	
	

		public static byte [] getData(){
			
			HttpURLConnection.setFollowRedirects(false);
			HttpURLConnection conn;
		    ByteArrayOutputStream  boi =new ByteArrayOutputStream();
			
			try {
			    String urlStr = "http://chart.apis.google.com/chart?cht=lc&chs=300x250&chxt=x%2Cy&chxs=$&chxl=0%3A|1%20amn|2%20am|3%20am|4%20am|5%20am&chdlp=bv&chco=ff7f00%2C339999%2Ccc9966&chxr=1%2C59%2C1170&chd=t:40,20,50,20,100|75,74,66,30,10";
			    URL url = new URL(urlStr);
			    conn = (HttpURLConnection) url.openConnection();
			    conn.setRequestMethod("GET");
			    int ii = -1;
			    try {
			        BufferedReader inp = new BufferedReader(new InputStreamReader(
			            conn.getInputStream()));
			        while (( ii = inp.read()) != -1) {
			        	boi.write(ii);
			            }
			        inp.close();
			        
			        } catch (Exception e) {
			        
			        }
			} catch (IOException e) {
			    e.printStackTrace();
			}
			return boi.toByteArray();
		}
}

  

Thanks,
Bharat

[Tom Reilly]

Note that this is a guess because I've never done this exact thing before. Could it be that you are reading a single character (16 bits), putting it in an int (32 bits) and then writing an int (but the documentation says that this writes a byte (8 bits)? Why don't you try isolating the read/write logic and put it into a simple test program (main). Read a file, write to a new file and see if they are the same.

[Bharat Makwana]

Hi Tom,

Thank you very much for your time and reply, problem solved. There was a silly mistake in my previous code.
updated code for getData() method would be

   
public byte[] getData() {
		InputStream in = null;
		ByteArrayOutputStream imageByte = new ByteArrayOutputStream(1024);
		try {
			HttpURLConnection conn;
			String urlStr = "http://chart.apis.google.com/chart?cht=lc&chs=300x250&chxt=x%2Cy&chxs=$&chxl=0%3A|1%20amn|2%20am|3%20am|4%20am|5%20am&chdlp=bv&chco=ff7f00%2C339999%2Ccc9966&chxr=1%2C59%2C1170&chd=t:40,20,50,20,100|75,74,66,30,10";
		    URL url = new URL(urlStr);
		    conn = (HttpURLConnection) url.openConnection();
		    conn.setRequestMethod("GET");
			byte[] data = new byte[1024];

			in = conn.getInputStream();
			int length;
			while ((length = in.read(data)) != -1) {
				imageByte.write(data, 0, length);
			}
		} catch (IOException ex) {
			ex.printStackTrace();
		} finally {
			if (in != null) {
				try {
					in.close();
				} catch (IOException ex) {
					ex.printStackTrace();
				}
			}
		}
		System.out.println("Returning Image............");
		return imageByte.toByteArray();
	}
 

Thanks again,
Bharat