0
我有一个jsp页面(说,MyJspPage.jsp
) -对ArrayList的循环改变对象
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<%
ArrayList<Person> ownerList = (ArrayList<Person>) request
.getAttribute("ownerList");
//set again ..
request.setAttribute("ownerList",ownerList) ;
%>
</head>
<body>
<%
//itr on all the persons ..;
for (Person person : ownerList) {
%>
// some HTML code..
<%
}
%>
<form action="servlet123" method="POST">
// some fields ..
<input type="submit" value="join" />
</form>
</body>
</html>
和一个servlet -
@WebServlet("/servlet123")
public class servlet123 extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// get the then set ..
ArrayList<Person> ownerList = (ArrayList<Person)request.getAttribute("ownerList");
request.setAttribute("ownerList", ownerList);
// forward to `MyJspPage.jsp`
dispather.forward(request, response);
}
}
首先另一个servlet着MyJspPage.jsp
,它做工精细,那么就有像MyJspPage.jsp
和servlet123
之间的乒乓球。问题是,当在第二次reachs到MyJspPage.jsp
它抛出一个异常 -
type Exception report
message java.lang.NullPointerException
description The server encountered an internal error (java.lang.NullPointerException) that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
应当注意的是,当我省略了从MyJspPage.jsp循环并改变它是 -
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<%
ArrayList<Person> ownerList = (ArrayList<Person>) request
.getAttribute("ownerList");
//set again ..
request.setAttribute("ownerList",ownerList) ;
%>
</head>
<body>
<form action="servlet123" method="POST">
// some fields ..
<input type="submit" value="join" />
</form>
</body>
</html>
MyJspPage.jsp
和servlet123
之间的所有关系都可以正常工作。
我首先检查ownerList是否不为空,确保它已传递到您的页面 – MadProgrammer 2012-08-11 21:53:11
请求对象是每个请求的新对象。您应该保存并从会话中检索列表。 – 2012-08-11 21:56:44
@BheshGurung有没有办法根据要求做到这一点? – URL87 2012-08-11 22:00:38