JSP Servlet检索（显示）网页

Question

I am writing a servlet in JSP page to display the requested webpage. I have done fair bit of "googling" and most of them suggested of using BufferedReader. Below I have the code that gets the requested url from the JSP page and the servlet displays the page.

However, while running this I am getting blank from the servlet. Could anyone suggest me what wrong I have been doing in this code?

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String server = request.getParameter("browsebox");

        URL url = new URL(server);
        URLConnection yc = url.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(
                yc.getInputStream(), "UTF-8"));
        String inputLine;
        StringBuilder a = new StringBuilder();
        while ((inputLine = in.readLine()) != null)
            a.append(inputLine);
        in.close();

       PrintWriter out = response.getWriter();
        out.println(a);
        // String output= a.toString();
        //System.out.println(output);
    }

Answer 1

You are very, very close. But why are you printing the target web page on console rather than sending it back to the client? Try this for starters:

response.getWriter().println(a);

Once you overcome that problem think how can you avoid loading the whole target web page first to a String and then sending it back. What about reading target web page line by line or byte by byte and sending it immediately? Not only the client will receive partial response earlier, but you will save a lot of memory.

Answer 2

You need to get the PrintWriter object from the response object.

PrintWriter writer = response.getWriter();
writer.println(<value>);

Answer 3

After you add

PrintWriter out=response.getWriter();
out.println(a);

it should work. Still if it is not working try,

PrintWriter out=response.getWriter();
out.println(a);`
out.flush();