Question

我想知道测试条件jstl If -

boolean cbtest1=interests[0]!=null;//cbtest1 is true

这是我的jsp代码 -

<td >interest1
<c:choose> 
<c:when test="${cbtest1}">
<input type="checkbox"  name="interest1" checked/>
</c:when>
<c:otherwise>
<input type="checkbox"  name="interest1" />
</c:otherwise>
</c:choose>
</td>

但是当我渲染页面时，otherwise块被执行了！

我也测试了以下 -

<c:when test="${interests[0]!=null}">

在这种情况下otherwise也已执行。

当我使用negation -

进行测试时，这让我更加奇怪

<c:when test="${interests[0]==null}">

或 -

<c:when test="${!cbtest1}">

上面两个案例when已执行。我错了吗？

interests[0]的值为"y"，而cbtest的值为true。

附加了页面的屏幕截图，其中显示了cbtest和interest [o]的值，即interest1正在显示。 enter image description here

正如JBNIZT建议的那样 - 我做了以下更改，我在请求中设置了布尔数组而不是字符串数组.-

Servlet1.java

@WebServlet("/serv")
public class servlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        String username=request.getParameter("username").trim();
        String password=request.getParameter("password").trim();
        System.out.println("Hellow! "+username);
        try{

            Connection con=CommonUtil.getConnection();
            Statement st=con.createStatement();



            ResultSet rs=st.executeQuery("select * from login");
            int flag=0;
            while(rs.next()){
                if(rs.getString(1).trim().equals(username)&&rs.getString(2).trim().equals(password)){
                    flag=1;
                    HttpSession session=request.getSession();
                    session.setAttribute("loginId", rs.getString(3).trim());

                    ResultSet rs1=st.executeQuery("select * from details where loginid='"+ rs.getString(3).trim()+"'");
                    rs1.next();
                    String name=rs1.getString(1);
                    String address=rs1.getString(2);
                    String hobby=rs1.getString(4);

                    ResultSet rs2=st.executeQuery("select * from interest where loginid='"+session.getAttribute("loginId")+"'");
                    rs2.next();
                    String interest1=rs2.getString(2);
                    String interest2=rs2.getString(3);
                    String interest3=rs2.getString(4);

                    request.setAttribute("name", name);
                    request.setAttribute("address", address);
                    request.setAttribute("hobby", hobby);

                    boolean[] interest={(interest1!=null),(interest2!=null),(interest3!=null)};
                    request.setAttribute("interest", interest);



                    System.out.println(interest1+interest2+interest3);

                    System.out.println(name+address+hobby);
                    request.getRequestDispatcher("display.jsp").forward(request, response);
                    return;
                }
            }
            if(flag==0){
                request.setAttribute("message", "invalide login credentials!");
                request.getRequestDispatcher("index.jsp").forward(request, response);
                                return;
            }
        }catch(Exception e){
            System.out.println(e);
        }
    }

}

display.jsp

<%@ page language="java" contentType="text/html"%>
<%@page import="java.sql.Connection" import="java.util.Enumeration" import="java.sql.ResultSet"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
hellow!!


<%
out.println(session.getAttribute("loginId"));
String  name=(String)request.getAttribute("name");
String  address=(String)request.getAttribute("address");
String  hobby=(String)request.getAttribute("hobby");
boolean[]  interests=(boolean[])request.getAttribute("interest");




out.println(name+"</br>address- "+address+"</br>hobby- "+hobby+"</br>Interest1- "+interests[0]+"</br>Interest2- "+interests[1]+"</br>Interest3- "+interests[2]+"</br>interests- "+interests);
%>
<form action="updateServ" method="post">
  <table>
    <tr >
    <td >Name:</td>
    <td ><input type="text"  name="username" value="${name}"/></td>
    </tr>

    <tr>
    <td> Address:</td>
    <td ><input type="text"  name="address" value="${address}"/></td>
    </tr>
   </table>

   <table>
     <tr >
     <td >interest1
       <c:choose> 
        <c:when test="${interests[0]}">
            <input type="checkbox"  name="interest1" checked/>
        </c:when>
        <c:otherwise>
            <input type="checkbox"  name="interest1" />
        </c:otherwise>
       </c:choose>
     </td>

    <td >interest2<input type="checkbox"  name="interest2" /></td>
    <td >interest3<input type="checkbox"  name="interest3" /></td>
    </tr>

    <tr>
     <td >Hobby1<input type="radio" value="hobby1" name="hobby"/></td>
    <td >Hobby2<input type="radio" value="hobby2" name="hobby"/></td>
    <td >Hobby3<input type="radio" value="hobby3" name="hobby"/></td>
    </tr>
    <tr>
    <td></td>
    <td><input type="submit" value="Update"></td>
    <td></td>
    </tr>
   </table>
</form>

这仍然无效。

使用jstl时测试条件不良导致如果 -

0 个答案: