从mysql数据库检索下拉列表并将其插入到jsp中的数据库 [英] retrieve dropdown list from mysql database and insert to database in jsp

问题描述

这件事真的让我感到困扰.如何从MySQL数据库获取下拉列表，然后将其提交到JSP中的另一个表.我只知道如何使用html创建静态下拉列表，但是如何使它动态化.我正在考虑一种链接到servlet的形式，该servlet连接到数据库并从数据库表中获取字符串数组，然后将其发送到JSP以填充选项，并且在提交选项时，它将发送到然后将servlet插入数据库.有人请给我一些可以做到这一点的示例代码.最具体地说，我需要标记中使用的JSP代码和从servlet发送的代码.我已经与Google核实过，但没有明确的答案.希望我在这里得到答案

This thing is really bothering me. How can I get my dropdown list from MySQL database and then submit it to another table in JSP. I only know how to create a static dropdown with html and but how can I make it dynamic. I am thinking of a form that links to a servlet and the servlet connects to the database and fetches an array of strings from a database table and then sends it to the JSP to populate the options and when an option is submitted, it send to a servlet which then inserts to the database. someone please give me some sample code that can do this. Most specifically I need the code of the JSP used in the tag and the code for sending from the servlet. I've really checked with google but there is no clear answer. Hope I get an answer here

推荐答案

您几乎完全正确.要从数据库中获取下拉列表值，您应该首先调用执行预处理工作的servlet，然后让servlet显示带有下拉列表的JSP.

You've it almost right. To get the dropdown values from a database you should first call the servlet which does the preprocessing job and then let the servlet display the JSP with the dropdown.

由于正常的HTTP请求(单击链接，书签或在地址栏中输入URL)会按定义触发GET请求，因此您想在doGet()方法中执行此操作.这是一个以List<Product>风格获得下拉值的示例.

Since a normal HTTP request (clicking a link, a bookmark or entering the URL in address bar) fires per definition a GET request, you'd like to do the job in the doGet() method. Here's an example which gets the dropdown values in flavor of a List<Product>.

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    List<Product> products = productService.list();
    request.setAttribute("products", products); // It'll be available as ${products}.
    request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response);
}

在/WEB-INF/products.jsp中，您可以将其显示如下:

In /WEB-INF/products.jsp you can display it as follows:

<form action="order" method="post">
    <select name="productId">
        <c:forEach items="${products}" var="product">
            <option value="${product.id}">${product.name}</option>
        </c:forEach>
    </select>
    <input type="submit" value="Order" />
</form>

将此servlet映射到/products的URL模式上，并通过 http://example.com/进行调用上下文/产品.它将从数据库加载产品，将其存储在请求范围内，再转发给JSP进行展示.

Map this servlet on an URL pattern of /products and invoke it by http://example.com/context/products. It'll load the products from the DB, store it in the request scope, forward to the JSP to let it present it.

提交表单时，将调用servlet的doPost()方法，该方法映射到/order的URL模式上.提交HTML表单时，每个输入元素的name=value对将可用作HTTP请求参数.因此，您可以获得以下产品ID:

When you submit the form, then the doPost() method of a servlet which is mapped on an URL pattern of /order will be invoked. When you submit a HTML form, then the name=value pair of every input element will be available as a HTTP request parameter. So you can get the product ID as follows:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String productId = request.getParameter("productId");
    // ... do your job here to insert the data.

    request.getRequestDispatcher("/WEB-INF/someresult.jsp").forward(request, response);
}

另请参见:

• 我们的JSP Wiki页面
• 我们的Servlets Wiki页面

See also:

• Our JSP wiki page
• Our Servlets wiki page

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