<%@ page import="java.io.*" %>
<%
String[] permitted = { "counter.jsp", "environment.jsp", "guestbook.jsp",
    "guestbookpost.jsp", "SetColor.jsp", "Greeting.jsp", "shopforbooks.jsp",
    "time.jsp", "ViewJavaSource.jsp" };
String filename = "ViewJavaSource.jsp";
String fileParameter = request.getParameter("file");
if (fileParameter != null)
    for (int i = 0; i < permitted.length; i++)
        if (fileParameter.equals(permitted[i]))
            filename = fileParameter;
response.setContentType("text/plain");
try {
    String fileToView = application.getRealPath("/book/21javapre/source/chapter27/" + filename);
    FileReader reader = new FileReader(fileToView);
    BufferedReader in = new BufferedReader(reader);
    boolean eof = false;
    while (!eof) {
        String line = in.readLine();
        if (line == null)
            eof = true;
        else
            out.print(line + "\r\n");
    }
    in.close();
} catch (IOException e) {
    out.println("Error -- " + e.toString());
}
%>