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POSimple Servlet and Nullpointerexception (error 500)
 

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  1. POSimple Servlet and Nullpointerexception (error 500)
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    <p>I get following error after trying to launch my first servlet... what may be wrong? I am using proper method (get) and the same code works for my friend... is it possible to be tomcat's fault?</p> <pre><code>org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet Ciastko threw exception java.lang.NullPointerException </code></pre> <p>DOGET method:</p> <pre><code>protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub response.setContentType("text/html;charset=UTF-8"); HttpSession sesja = request.getSession(true); PrintWriter out = response.getWriter(); String login = request.getParameter("login"); String pass = request.getParameter("pass"); if(login.isEmpty() || pass.isEmpty()){ out.println("Brak sesji lub atrybutu."); } if(login.equals("admin") || pass.equals("admin")){ out.println("ADMIN"); } else{ sesja.setAttribute("login", login); sesja.setAttribute("pass", pass); } } </code></pre> <p>and here is index.html file:</p> <pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" http://www.w3.org/TR/html4/loose.dtd"&gt; &lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8"&gt; &lt;title&gt;Tytuł&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;form action="Ciastko" method="GET"&gt; &lt;p&gt;Login: &lt;/p&gt;&lt;input name="login" id="login" /&gt; &lt;p&gt;Hasło: &lt;/p&gt;&lt;input name="pass" id="pass" /&gt; &lt;input type="submit" value="Wyślij!" /&gt; &lt;/form&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>
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    1. COhow did you define the servlet? edit and add your web.xml or @servlet definition please
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    2. COcan you show the full stack trace ?
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    3. COwell the problem I see is that after starting it it automatically "runs" form button. So it always started it with null form values, and that is why there was an exception. When I changed method to: ` if(login==null || pass==null){ out.println("NO ATRIBUTE"); } ` It does not even print the form from index.html, but automatically the NO ATTRIBUTE text... what may be wrong?
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