在jsp页面中下载.pdf

Question

I'm writing a web app with jsp and servlets. I want to have a different pdf file for each picture in jsp page. I thing that I should send id to the servet and there for that id to get right pdf.Can you give me some help with that.

protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet rs = null;
    try {
        connection = WebDBConnectionsPool.getConnection();
    } catch (Exception e1) {
        e1.printStackTrace();
    }

    try {

        String filepath = null;
        String bookId = request.getParameter("id");

        statement = connection.prepareStatement("SELECT filepath FROM books WHERE bookid=?");
        statement.setString(1, bookId);
        rs = statement.executeQuery();
        while (rs.next()) {

            filepath = rs.getString("filepath");
        }
            String path = filepath;
            File downloadFile = new File(path);
            FileInputStream inStream = new FileInputStream(downloadFile);

            // if you want to use a relative path to context root:
            String relativePath = getServletContext().getRealPath("");
            System.out.println("relativePath = " + relativePath);

           File pdfFolder =
                         new File(request.getSession().getServletContext().getRealPath("/pdf"));

           // obtains ServletContext
           ServletContext context = getServletContext();

           // gets MIME type of the file
           String mimeType = context.getMimeType(filePath);
           if (mimeType == null) {        
               // set to binary type if MIME mapping not found
               mimeType = "application/octet-stream";
           }
    //        System.out.println("MIME type: " + mimeType);

           // modifies response
           response.setContentType(mimeType);
           response.setContentLength((int) downloadFile.length());

           // forces download
           String headerKey = "Content-Disposition";
           String headerValue = String.format("attachment; filename=\"%s\"", downloadFile.getName());
           response.setHeader(headerKey, headerValue);

           // obtains response's output stream
           OutputStream outStream = response.getOutputStream();

           byte[] buffer = new byte[4096];
           int bytesRead = -1;

           while ((bytesRead = inStream.read(buffer)) != -1) {
               outStream.write(buffer, 0, bytesRead);
           }

           inStream.close();
           outStream.close();     
       }






   <% 
         for (int i = 0; i < data.getBooks().size(); i++) {
               Book book = (Book)data.getBooks().get(i);
         %>
       <article class="ebook cf">
          <img src="<%=book.getBookImage()%>">
          <div class="ebooks-description">
             <h4><%=book.getBookName()%></h4>
             <form>
                <input type="button" value="download" onclick="downloadFileAsynch('../DownloadFileServlet?id=<%=book.getBookId() %>');"/>
             </form>
          </div>
        </article> 
         <% } %>




 <script>
        function downloadFileAsynch(url){
        var elemIF = document.createElement("iframe");
        elemIF.name="file";
        elemIF.src = url;
        elemIF.style.display = "none";
        document.body.appendChild(elemIF);
        }
     </script>

Answer 1

In a console java program, if the file you want to read is under the directory as the code you are running, you can read it by like "./pdf/ebook01.jpg" but in a servlet it doesn't work that way. In a servlet, your "./" will need to be replaced with context.getRealPath("/") :

context.getRealPath("/") + "/pdf/ebook01.jpg"

Ok, so looking at your code again, you apparently know that(?) just your code is ridiculously messy and inconsistent so you saved the path into a variable (or tried to) and then never actually used the variable.

You have String relativePath = getServletContext().getRealPath(""); and a little later request.getSession().getServletContext().getRealPath("/pdf") and later ServletContext context = getServletContext(); How about some consistency and organization?

ServletContext context = getServletContext();
String relativePath = context.getRealPath("/");

And then make sure wherever you are reading the file you actually use relativePath ...