JSP getParameterValues返回Null

Question

我正在使用JSTL标签和EL从我的数据库中获取值。 我在UI上的数据表中添加了一个复选框，用于删除记录。 问题是servlet中的String []总是以null出现，我不知道为什么。 我什至在复选框元素的'值'属性中尝试了伪数据，并且该数组仍然为空。

的HTML

             <div id="authorTable" >
            <table style="text-align: center;">

                <thead>
                <th>Book ID</th>
                <th>Title</th>
                <th>Date Published</th>
                <th>Author ID</th>
                <th>Author First Name</th>
                <th>Author Last Name</th>
                <th>Delete</th>
                </thead>

                <tbody>
                    <c:forEach var="record" items="${bookRecordsResult}">
                        <tr>
                            <td>${record.bookID}</td>
                            <td>${record.title}</td>
                            <td>${record.datePublished}</td>
                            <td>${record.author.firstName}</td>
                            <td>${record.author.lastName}</td>
                            <td>${record.author.id}</td>
          This Line ------> <td> <input type="checkbox" name="boxes" id="boxes" class="boxes" value="${record.bookID}" /> </td>
                        </tr>
                    </c:forEach>
                </tbody>
            </table>
        </div>

        <div id="deleteContainer">
            <form id="deleteForm" method="POST" action="bookAuthorControls">
                <button type="submit" id="deleteButton" name="deleteButton" >Delete</button>
            </form>
        </div>

Java Servlet

  String delete = request.getParameter("deleteButton");

    if (delete != null) {
       And This Line ---->  String[] checkValues = request.getParameterValues("boxes");

        try {
       service.deleteRecords(Arrays.asList(checkValues));
            bookRecords = service.getAllBookRecords();
            request.setAttribute("bookRecordsResult", bookRecords);
        } catch (SQLException | ClassNotFoundException | ParseException ex) {
            request.setAttribute("error", ex.getLocalizedMessage());
        }
    }

无论我尝试什么，String []再次返回null，有什么想法吗？

Answer 1

复选框输入元素不包含在提交的表单元素中。

您需要将表单包装在所有输入元素周围：

<form id="deleteForm" method="POST" action="bookAuthorControls">
    <div id="authorTable">
         ...
         <td><input type="checkbox" name="boxes" id="boxes" class="boxes" value="${record.bookID}" /> </td>
         ...
    </div>

    <div id="deleteContainer">
        <button type="submit" id="deleteButton" name="deleteButton"       >Delete</button>
    </div>
</form>