小编典典

具有JSP / Servlet和Ajax的简单计算器

javascript

我想在jsp中创建一个简单的计算器。将有两个用于数字的文本框和一个添加按钮。理想情况下,我希望答案不重新加载就显示在页面中,但是从我得到的答案来看,它似乎对我的规模来说太大了。我可以想到:1)将答案打印到第三个文本框(有可能吗?),或者以某种方式将答案与相同的页面(带有添加按钮和全部)一起加载(并能够输入不同的数字,依此类推)

您能建议一个好的方法吗?


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2020-05-01

共1个答案

小编典典

对于我的规模来说似乎太大了

这实际上取决于上下文和功能要求。这是非常简单和琐碎的。它更多的声音一样,它的“太多信息”为你和你实际需要学习不同的概念(HTTP,HTML,CSS,JS,Java和JSP,Servlet的,AJAX,JSON等)
单独
使大局观(所有这些语言/技术的总和)变得更加明显。您可能会发现此答案很有用。

无论如何,这是仅使用JSP / Servlet而不使用Ajax的方法:

calculator.jsp

<form id="calculator" action="calculator" method="post">
    <p>
        <input name="left">
        <input name="right">
        <input type="submit" value="add">
    </p>
    <p>Result: <span id="result">${sum}</span></p>
</form>

CalculatorServlet其被映射上url-pattern/calculator

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    Integer left = Integer.valueOf(request.getParameter("left"));
    Integer right = Integer.valueOf(request.getParameter("right"));
    Integer sum = left + right;

    request.setAttribute("sum", sum); // It'll be available as ${sum}.
    request.getRequestDispatcher("calculator.jsp").forward(request, response); // Redisplay JSP.
}

使Ajaxical的东西起作用也不难。只需在JSP的HTML中包含以下JS <head>(请向右滚动以查看代码注释,其中解释了每一行的作用):

<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>
    $(document).ready(function() {                                                   // When the HTML DOM is ready loading, then execute the following function...
        $('#calculator').submit(function() {                                         // Locate HTML element with ID "calculator" and execute the following function on its "submit" event...
            $form = $(this);                                                         // Wrap the form in a jQuery object first (so that special functions are available).
            $.post($form.attr('action'), $form.serialize(), function(responseText) { // Execute Ajax POST request on URL as set in <form action> with all input values of the form as parameters and execute the following function with Ajax response text...
                $('#result').text(responseText);                                     // Locate HTML element with ID "result" and set its text content with responseText.
            });
            return false;                                                            // Prevent execution of the synchronous (default) submit action of the form.
        });
    });
</script>

doPost如下更改最后两行:

    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");
    response.getWriter().write(String.valueOf(sum));

您甚至可以对其进行条件检查,以便您的表单在用户禁用JS的情况下仍然可以使用:

    if ("XMLHttpRequest".equals(request.getHeader("X-Requested-With"))) {
        // Ajax request.
        response.setContentType("text/plain");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(String.valueOf(sum));
    } else {
        // Normal request.
        request.setAttribute("sum", sum);
        request.getRequestDispatcher("calculator.jsp").forward(request, response);
    }
2020-05-01