java 将隐藏的输入值从 jsp 传递到 servlet
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Passing hidden input value from jsp to servlet
提问by Amber
I'm trying to generate an excel file when a link is clicked without being redirected anywhere. I make it into the servlet but when I try to get the value of a hidden input, I get a null pointer exception. The code I'm using is
我试图在单击链接时生成一个 excel 文件而没有被重定向到任何地方。我将它放入 servlet，但是当我尝试获取隐藏输入的值时，我得到一个空指针异常。我使用的代码是
JSP
JSP
<html:form action="/UploadExcel.do" enctype="multipart/form-data" method="post">
<a href="#" onclick="ExcelFiller.fill">Download Excel</a>
<input type="hidden" name="refBgcId" id="refBgcId" value="84"></input>
</html:form>
Servlet
小服务程序
public class ExcelFiller extends HttpServlet {
private static final long serialVersionUID = 1L;
public void init(ServletConfig config) throws ServletException {
super.init(config);
}
public void destroy() {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("Made it to the servlet");
doPost(request,response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("In doPost");
HttpSession session=(HttpSession) request.getSession(false);
String loggedInUserId = (String)session.getAttribute("strUserId");
try{
String referenceid = request.getParameter("refBgcId").toString();/*NULL POINTER EXCEPTION*/
ArrayList<String> details = new ArrayList<String>();
details = UploadBGCDAO.getDetails(referenceid);
createExcel(request,response,details, loggedInUserId);
} catch (Exception e) {
e.printStackTrace();
}
}
}
I have tried finding the solution in the answers to similar questions on this site but I still can't make this work. Can someone please tell me what I'm doing wrong?
我已经尝试在本网站上类似问题的答案中找到解决方案，但我仍然无法完成这项工作。有人可以告诉我我做错了什么吗？
回答by Brijesh Bhatt
Input parameter will be passed to the servlet only when you submit a form, not when your anchor tag is clicked.
输入参数只会在您提交表单时传递给 servlet，而不是在单击锚标记时传递给 servlet。
If you want to pass a parameter append the parameter in a query String.
如果要传递参数，请将参数附加到查询字符串中。
回答by saikumarm
<form action="ExcelFiller.fill">
<input type="hidden" name="refBgcId" id="refBgcId" value="84"></input>
<input type="submit" value="Download Excel"></input>
</form>
and in the servlet make the following changes.
the name of the attribute is refBgcId.
change the statement
并在 servlet 中进行以下更改。属性的名称是refBgcId. 更改声明
String referenceid = request.getParameter("ref_id").toString();
String referenceid = request.getParameter("ref_id").toString();
to
到
String referenceid = request.getParameter("refBgcId").toString();
String referenceid = request.getParameter("refBgcId").toString();
回答by Prashant
you can pass parameters in URL in Java Script as :
您可以在 Java Script 中将 URL 中的参数传递为：
var refBgcId=84;
var url = "/UploadExcel.do?refBgcId="+refBgcId;
window.location.href =url;
and in servlet you can access as
在 servlet 中，您可以访问为
String refBgcId= request.getParameter("refBgcId").toString();
回答by Jayant
String referenceid = request.getParameter("refBgcId").toString(); // here refBgcId is a name...dont confuse with name and Id pass name from jsp
String referenceid = request.getParameter("refBgcId").toString(); // 这里 refBgcId 是一个名称...不要与来自 jsp 的名称和 Id 传递名称混淆
and then in servlet try this
然后在servlet中试试这个
String referenceid = request.getParameter("refBgcId").toString();
String referenceid = request.getParameter("refBgcId").toString();
