I try to explain quickly and in detail what I plan to do. I've the following JSP page:
我试着快速详细地解释我打算做什么。我有以下JSP页面：
JSP
JSP
<!DOCTYPE html>
<html lang="en">
<head>
<style>
.AreaFree {
-moz-box-shadow: inset 0px 1px 0px 0px #3dc21b;
-webkit-box-shadow: inset 0px 1px 0px 0px #3dc21b;
background-color: #44c767;
border: 1px solid #18ab29;
display: inline-block;
cursor: pointer;
color: #ffffff;
font-family: Arial;
font-size: 16px;
font-weight: bold;
padding: 15px 21px;
text-decoration: none;
}
.AreaFree:hover {
background-color: #5cbf2a;
}
.AreaFree:active {
position: relative;
}
.AreaOccupated {
-moz-box-shadow: inset 0px 1px 0px 0px #3dc21b;
-webkit-box-shadow: inset 0px 1px 0px 0px #3dc21b;
background-color: #E00000;
border: 1px solid #B00000;
display: inline-block;
cursor: pointer;
color: #ffffff;
font-family: Arial;
font-size: 16px;
font-weight: bold;
padding: 15px 21px;
text-decoration: none;
}
.AreaOccupated:hover {
background-color: #D00000;
}
.AreaOccupated:active {
position: relative;
}
.AreaBlocked {
-moz-box-shadow: inset 0px 1px 0px 0px #3dc21b;
-webkit-box-shadow: inset 0px 1px 0px 0px #3dc21b;
background-color: #A8A8A8;
border: 1px solid #808080;
display: inline-block;
cursor: pointer;
color: #ffffff;
font-family: Arial;
font-size: 16px;
font-weight: bold;
padding: 15px 21px;
text-decoration: none;
}
.AreaBlocked:hover {
background-color: #989898;
}
.AreaBlocked:active {
position: relative;
}
input.clicked {
background-color: red;
}
</style>
<script src="https://code.jquery.com/jquery-1.11.3.js"></script>
</head>
<body>
<form action="myServlet" method="post">
<table cellspacing="0" cellpadding="0">
<tr>
<td>
<input type="button" class="AreaFree" id="11" />
</td>
<td>
<input type="button" class="AreaFree" id="12" />
</td>
<td>
<input type="button" class="AreaFree" id="13" />
</td>
<td>
<input type="button" class="AreaFree" id="14" />
</td>
<td>
<input type="button" class="AreaFree" id="15" />
</td>
</tr>
<tr>
<td>
<input type="button" class="AreaFree" id="21" />
</td>
<td>
<input type="button" class="AreaFree" id="22" />
</td>
<td>
<input type="button" class="AreaFree" id="23" />
</td>
<td>
<input type="button" class="AreaFree" id="24" />
</td>
<td>
<input type="button" class="AreaFree" id="25" />
</td>
</tr>
<input type="hidden" id="matrix" value="" />
<input type="hidden" value="callServlet" name="whatsend">
<input type="submit" value="submit">
</form>
<script>
var matrix = [];
for (var i = 0; i < 100; i++) {
matrix.push(0);
}
// set the hidden field on init
$('#matrix').val(matrix);
$('input[type="button"]').on('click', function(evt) {
var me = $(this);
var idx = +me.attr('id'); // the + sign turns this value to a number
if (matrix[idx] === 0) {
matrix[idx] = 1;
me.addClass('AreaBlocked');
} else {
matrix[idx] = 0;
me.removeClass('AreaBlocked');
}
// update the hidden field every time a user clicks something
$('#matrix').val(matrix);
});
</script>
</body>
</html>
Principally, in the following JSP page there is a table of buttons. Each button represents an area; the user decides to click on various buttons and these change color and status (on-off). Once the user select the buttons that he wants, press the submit button and send an array called "matrix" to a servlet, that containing information on each button pressed or not (boolean 0 or 1).
原则上，在以下JSP页面中有一个按钮表。每个按钮代表一个区域;用户决定点击各种按钮，这些按钮会改变颜色和状态（开 - 关）。一旦用户选择了他想要的按钮，按下提交按钮并将一个名为“矩阵”的数组发送到一个servlet，该数组包含按下或不按下每个按钮的信息（布尔值0或1）。
That's what I do in the servlet "myServlet"
这就是我在servlet“myServlet”中所做的
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
String whatsend = request.getParameter("whatsend");
if(whatsend.equals("callServlet")){
String matrix = request.getParameter("matrix");
}
}
catch (SQLException ex) {
}
}
Well, once you press the submit button the servlet is called, enters in the if block and executes the command request.getParameter, but unfortunately matrix is null. Where am I wrong? How do I move that array to this servlet? Could you kindly share the correct code? Thanks in advance, I'm sorry if I wasn't not much detailed.
好吧，一旦按下提交按钮，就会调用servlet，进入if块并执行命令request.getParameter，但遗憾的是矩阵为空。我哪里错了？如何将该数组移动到此servlet？你能分享正确的代码吗？在此先感谢，如果我不是很详细，我很抱歉。
1 个解决方案
#1
1
In your code, the form does not send any parameter named "matrix", because there's no input with name="matrix". So the first thing you have to do is to change that:
在您的代码中，表单不会发送任何名为“matrix”的参数，因为没有name =“matrix”的输入。所以你要做的第一件事就是改变它：
<input type="hidden" id="matrix" value="" />
into that:
进入：
<input type="hidden" id="matrix" name="matrix" value="" />
Then, you will have to consider how are you serializing the matrix. An input can only hold a value of type string (and only strings can be sent to the server) so you have to serialize the array into a string. That is usually (but not necessarily) accomplished through JSON. You would first convert the matrix to a JSON string before setting it as a value for the input:
然后，您将不得不考虑如何序列化矩阵。输入只能保存string类型的值（并且只能将字符串发送到服务器），因此您必须将数组序列化为字符串。这通常是（但不一定）通过JSON完成的。在将矩阵设置为输入值之前，首先将矩阵转换为JSON字符串：
$('#matrix').val(JSON.stringify(matrix));
And then in the server you would have to convert it back to an array. You can use several libraries for that. Two common options are JSON in Java and Google's Gson. The following example uses Gson and assumes that the seralized value is always an array of integers:
然后在服务器中，您必须将其转换回数组。您可以使用多个库。两个常见的选项是Java中的JSON和Google的Gson。以下示例使用Gson并假定seralized值始终是整数数组：
String matrixStr = request.getParameter("matrix");
Gson gson = new Gson();
Integer[] matrix = gson.fromJson(matrixStr, Integer[].class);
#1
1
In your code, the form does not send any parameter named "matrix", because there's no input with name="matrix". So the first thing you have to do is to change that:
在您的代码中，表单不会发送任何名为“matrix”的参数，因为没有name =“matrix”的输入。所以你要做的第一件事就是改变它：
<input type="hidden" id="matrix" value="" />
into that:
进入：
<input type="hidden" id="matrix" name="matrix" value="" />
Then, you will have to consider how are you serializing the matrix. An input can only hold a value of type string (and only strings can be sent to the server) so you have to serialize the array into a string. That is usually (but not necessarily) accomplished through JSON. You would first convert the matrix to a JSON string before setting it as a value for the input:
然后，您将不得不考虑如何序列化矩阵。输入只能保存string类型的值（并且只能将字符串发送到服务器），因此您必须将数组序列化为字符串。这通常是（但不一定）通过JSON完成的。在将矩阵设置为输入值之前，首先将矩阵转换为JSON字符串：
$('#matrix').val(JSON.stringify(matrix));
And then in the server you would have to convert it back to an array. You can use several libraries for that. Two common options are JSON in Java and Google's Gson. The following example uses Gson and assumes that the seralized value is always an array of integers:
然后在服务器中，您必须将其转换回数组。您可以使用多个库。两个常见的选项是Java中的JSON和Google的Gson。以下示例使用Gson并假定seralized值始终是整数数组：
String matrixStr = request.getParameter("matrix");
Gson gson = new Gson();
Integer[] matrix = gson.fromJson(matrixStr, Integer[].class);