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Writing a Servlet to View a Document in a Web Browser

by | Apr 24, 2012

This tech tip demonstrates how to write a simple servlet that allows any document supported by the RasterMaster imaging SDK library to be viewed in a standard Web browser. The documents are converted in real time to PNG images. package com.snowbound.techtip; import; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import Snow.Snowbnd; public class Document2PNGServlet extends HttpServlet { private final static int PNG_FORMAT = 43; private final static String IMAGE_DIRECTORY = “c:/images/”; public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletConfig config = getServletConfig(); ServletContext application = config.getServletContext(); Snowbnd snow = new Snowbnd(); // get the page number to convert from the page parameter int pageIndex = Integer.parseInt(request.getParameter(“page”)); // get the filename to convert from the filename parameter String filename = IMAGE_DIRECTORY + request.getParameter(“filename”); // create a temporary byte array that is at least as big as the expected output size byte[] tmpOutputBytes = new byte[15000000]; // decompress the specified page snow.IMG_decompress_bitmap(filename, pageIndex); // write out the page to a byte array in PNG format int outputSize = snow.IMG_save_bitmap(tmpOutputBytes, PNG_FORMAT); // copy only the data portion to our output array byte[] outputBytes = new byte[outputSize]; System.arraycopy(tmpOutputBytes, 0, outputBytes, 0, outputSize); // set the content type of the image data to be sent to the browser response.setContentType(application.getMimeType(“.png”)); response.setContentLength(outputSize); // send the bytes to the response object sendBytes(outputBytes, response); } /** * This method will send the contents of the byte array * to the servlet response output stream. * * @param bytes the output byte array * @param response the HttpServletResponse object to write to * @throws IOException */ protected void sendBytes(byte[] bytes, HttpServletResponse response) throws IOException { ServletOutputStream servletoutputstream = response.getOutputStream(); servletoutputstream.write(bytes); servletoutputstream.flush(); } } Learn More In addition to our Tech Tips section, our document and image Solutions Section provides business application and industry-specific examples including image conversion and web viewing.