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POfor loop on ArrayList change the object
 

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  1. POfor loop on ArrayList change the object
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    <p>I have a jsp page (says , <code>MyJspPage.jsp</code>) - </p> <pre><code>&lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt; &lt;% ArrayList&lt;Person&gt; ownerList = (ArrayList&lt;Person&gt;) request .getAttribute("ownerList"); //set again .. request.setAttribute("ownerList",ownerList) ; %&gt; &lt;/head&gt; &lt;body&gt; &lt;% //itr on all the persons ..; for (Person person : ownerList) { %&gt; // some HTML code.. &lt;% } %&gt; &lt;form action="servlet123" method="POST"&gt; // some fields .. &lt;input type="submit" value="join" /&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>And a servlet - </p> <pre><code>@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&lt;Person&gt; ownerList = (ArrayList&lt;Person)request.getAttribute("ownerList"); request.setAttribute("ownerList", ownerList); // forward to `MyJspPage.jsp` dispather.forward(request, response); } } </code></pre> <p>Firstly another servlet forward to <code>MyJspPage.jsp</code> and it work fine , then there is like ping pong between <code>MyJspPage.jsp</code> and <code>servlet123</code> . The problem is that when at the 2nd time reachs to <code>MyJspPage.jsp</code> it throws an exception - </p> <pre><code>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) </code></pre> <p>It should be noted that when I omit the for loop from MyJspPage.jsp and change it to be - </p> <pre><code> &lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt; &lt;% ArrayList&lt;Person&gt; ownerList = (ArrayList&lt;Person&gt;) request .getAttribute("ownerList"); //set again .. request.setAttribute("ownerList",ownerList) ; %&gt; &lt;/head&gt; &lt;body&gt; &lt;form action="servlet123" method="POST"&gt; // some fields .. &lt;input type="submit" value="join" /&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>all the relation between <code>MyJspPage.jsp</code> and <code>servlet123</code> returns work fine . </p>
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    1. PO
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    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USURL87
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    1. This table or related slice is empty.
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    1. PO
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    1. This table or related slice is empty.
    1. COI'd first check to see if the ownerList is not null, making sure that it's been passed to your page
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      1. POfor loop on ArrayList change the object
      1. USMadProgrammer
    2. CORequest object is new for each request. You should save and retrieve the list from the session.
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      1. POfor loop on ArrayList change the object
      1. USBhesh Gurung
    3. CO@BheshGurung is there any way to do it on request yet ?
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      1. USURL87
 

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