GetReqParam

// See also The Quintessential Servlet

// This method is called by the servlet container to process a GET request.
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    doGetOrPost(req, resp);
}

// This method is called by the servlet container to process a POST request.
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    doGetOrPost(req, resp);
}

// This method handles both GET and POST requests.
private void doGetOrPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    // Get the value of a request parameter; the name is case-sensitive
    String name = "param";
    String value = req.getParameter(name);
    if (value == null) {
        // The request parameter 'param' was not present in the query string
        // e.g. http://hostname.com?a=b
    } else if ("".equals(value)) {
        // The request parameter 'param' was present in the query string but has no value
        // e.g. http://hostname.com?param=&a=b
    }

    // The following generates a page showing all the request parameters
    PrintWriter out = resp.getWriter();
    resp.setContentType("text/plain");

    // Get the values of all request parameters
    Enumeration enum = req.getParameterNames();
    for (; enum.hasMoreElements(); ) {
        // Get the name of the request parameter
        name = (String)enum.nextElement();
        out.println(name);

        // Get the value of the request parameter
        value = req.getParameter(name);

        // If the request parameter can appear more than once in the query string, get all values
        String[] values = req.getParameterValues(name);

        for (int i=0; i<values.length; i++) {
            out.println("    "+values[i]);
        }
    }
    out.close();
}

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