Question

我正在通过Servlet上传图片。

try{
    //Image Upload Code
} catch(Exception e){
    //Exception Handler
} finally {
    request.setAttribute("job-id", jobId);
    request.setAttribute("message", message);
    System.out.println("SJA : " + message);
    getServletContext().getRequestDispatcher("ReloadJob.jsp").forward(request, response);
}

然后，在ReloadJob.jsp上，我试图使用这些附加属性：

String jobId = request.getParameter("job-id");
String message = request.getParameter("message");
System.out.println("RJ : " + jobId);
System.out.println("RJ : " + message);

整个过程打印以下输出：

SJA : MESSAGE RECEIVED
RJ : BYWEGRI76T46U34T
RJ : null

为什么消息变量为空？

Answer 1

尝试使用

   String message=(String)request.getAttribute("message");

Answer 2

getParameter()

getAttribute()返回http请求参数。那些从客户端传递到服务器。

<?php // CONFIG: Enable debug mode. This means we'll log requests into 'ipn.log' in the same directory. // Especially useful if you encounter network errors or other intermittent problems with IPN (validation). // Set this to 0 once you go live or don't require logging. define("DEBUG", 1); // Set to 0 once you're ready to go live define("USE_SANDBOX", 1); define("LOG_FILE", "./ipn.log"); // Read POST data // reading posted data directly from $_POST causes serialization // issues with array data in POST. Reading raw POST data from input stream instead. $raw_post_data = file_get_contents('php://input'); $raw_post_array = explode('&', $raw_post_data); $myPost = array(); foreach ($raw_post_array as $keyval) { $keyval = explode ('=', $keyval); if (count($keyval) == 2) $myPost[$keyval[0]] = urldecode($keyval[1]); } // read the post from PayPal system and add 'cmd' $req = 'cmd=_notify-validate'; if(function_exists('get_magic_quotes_gpc')) { $get_magic_quotes_exists = true; } foreach ($myPost as $key => $value) { if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) { $value = urlencode(stripslashes($value)); } else { $value = urlencode($value); } $req .= "&$key=$value"; } // Post IPN data back to PayPal to validate the IPN data is genuine // Without this step anyone can fake IPN data if(USE_SANDBOX == true) { $paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr"; } else { $paypal_url = "https://www.paypal.com/cgi-bin/webscr"; } $ch = curl_init($paypal_url); if ($ch == FALSE) { return FALSE; } curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_RETURNTRANSFER,1); curl_setopt($ch, CURLOPT_POSTFIELDS, $req); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1); curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2); curl_setopt($ch, CURLOPT_FORBID_REUSE, 1); if(DEBUG == true) { curl_setopt($ch, CURLOPT_HEADER, 1); curl_setopt($ch, CURLINFO_HEADER_OUT, 1); } // CONFIG: Optional proxy configuration //curl_setopt($ch, CURLOPT_PROXY, $proxy); //curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1); // Set TCP timeout to 30 seconds curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30); curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close')); // CONFIG: Please download 'cacert.pem' from "http://curl.haxx.se/docs/caextract.html" and set the directory path // of the certificate as shown below. Ensure the file is readable by the webserver. // This is mandatory for some environments. //$cert = __DIR__ . "./cacert.pem"; //curl_setopt($ch, CURLOPT_CAINFO, $cert); $res = curl_exec($ch); if (curl_errno($ch) != 0) // cURL error { if(DEBUG == true) { error_log(date('[Y-m-d H:i e] '). "Can't connect to PayPal to validate IPN message: " . curl_error($ch) . PHP_EOL, 3, LOG_FILE); } curl_close($ch); exit; } else { // Log the entire HTTP response if debug is switched on. if(DEBUG == true) { error_log(date('[Y-m-d H:i e] '). "HTTP request of validation request:". curl_getinfo($ch, CURLINFO_HEADER_OUT) ." for IPN payload: $req" . PHP_EOL, 3, LOG_FILE); error_log(date('[Y-m-d H:i e] '). "HTTP response of validation request: $res" . PHP_EOL, 3, LOG_FILE); } curl_close($ch); } // Inspect IPN validation result and act accordingly // Split response headers and payload, a better way for strcmp $tokens = explode("\r\n\r\n", trim($res)); $res = trim(end($tokens)); if (strcmp ($res, "VERIFIED") == 0) { // check whether the payment_status is Completed // check that txn_id has not been previously processed // check that receiver_email is your PayPal email // check that payment_amount/payment_currency are correct // process payment and mark item as paid. // assign posted variables to local variables //$item_name = $_POST['item_name']; //$item_number = $_POST['item_number']; //$payment_status = $_POST['payment_status']; //$payment_amount = $_POST['mc_gross']; //$payment_currency = $_POST['mc_currency']; //$txn_id = $_POST['txn_id']; //$receiver_email = $_POST['receiver_email']; //$payer_email = $_POST['payer_email']; if(DEBUG == true) { error_log(date('[Y-m-d H:i e] '). "Verified IPN: $req ". PHP_EOL, 3, LOG_FILE); } } else if (strcmp ($res, "INVALID") == 0) { // log for manual investigation // Add business logic here which deals with invalid IPN messages if(DEBUG == true) { error_log(date('[Y-m-d H:i e] '). "Invalid IPN: $req" . PHP_EOL, 3, LOG_FILE); } } ?>仅供服务器端使用 - 您可以使用可在同一请求中使用的属性填充请求。

例如 - 在servlet中设置属性，并从JSP中读取它。它可以用于任何对象，而不仅仅是字符串。

在Servlet RequestDispatcher中发送两个属性

2 个答案: