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POHow to debug servlet 404
 

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    <p>I have a servlet with url mapping <code>""</code>(empty string). It's supposed to be mapped to the context root (I'm using tomcat7 with eclipse).</p> <p>But sometimes when I refresh the browser, the page displays 404 page. And a quick fix is to re-run(inside eclipse). And after a while the same 404 error comes back. I'm very frustrated about this. Is there a way to trace how on earth a mapped url pattern can sometimes (most of the time is OK) lead to 404?</p> <p>EDIT 1: OK, here is the details of configuration and code: I have a apache httpd in front of the tomcat server. The request is forwarded using mod_proxy</p> <pre><code>&lt;IfModule mod_proxy_http.c&gt; ProxyPass /myapp http://127.0.0.1:8080/myapp ProxyPassReverse /myapp http://127.0.0.1:8080/myapp &lt;/IfModule&gt; </code></pre> <p>And here is the servlet: (processRequest is called by both doPost and doGet)</p> <pre><code> @WebServlet("") public class RootServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Root Servlet"); try { this.handleHomePage(request, response); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NamingException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private void handleHomePage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException, SQLException, NamingException { HttpSession session = request.getSession(false); if (session != null &amp;&amp; session.getAttribute(Config.SESSION_AUTH_EMAIL) != null) { String email = (String) session.getAttribute(Config.SESSION_AUTH_EMAIL); request.getRequestDispatcher("/WEB-INF/jsp/main/home.jsp").forward(request, response); } else { request.getRequestDispatcher("/WEB-INF/jsp/main/index.jsp").forward(request, response); } } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.processRequest(request, response); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.processRequest(request, response); } } </code></pre> <p>web.xml</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"&gt; &lt;error-page&gt; &lt;error-code&gt;404&lt;/error-code&gt; &lt;location&gt;/WEB-INF/jsp/error/404.jsp&lt;/location&gt; &lt;/error-page&gt; &lt;error-page&gt; &lt;error-code&gt;500&lt;/error-code&gt; &lt;location&gt;/WEB-INF/jsp/error/500.jsp&lt;/location&gt; &lt;/error-page&gt; &lt;servlet&gt; &lt;servlet-name&gt;info-about&lt;/servlet-name&gt; &lt;jsp-file&gt;/WEB-INF/jsp/info/about.jsp&lt;/jsp-file&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;info-about&lt;/servlet-name&gt; &lt;url-pattern&gt;/about&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;servlet&gt; &lt;servlet-name&gt;info-help&lt;/servlet-name&gt; &lt;jsp-file&gt;/WEB-INF/jsp/info/help.jsp&lt;/jsp-file&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;info-help&lt;/servlet-name&gt; &lt;url-pattern&gt;/help&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;servlet&gt; &lt;servlet-name&gt;info-contact&lt;/servlet-name&gt; &lt;jsp-file&gt;/WEB-INF/jsp/info/contact.jsp&lt;/jsp-file&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;info-contact&lt;/servlet-name&gt; &lt;url-pattern&gt;/contact&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;servlet&gt; &lt;servlet-name&gt;info-terms&lt;/servlet-name&gt; &lt;jsp-file&gt;/WEB-INF/jsp/info/terms.jsp&lt;/jsp-file&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;info-terms&lt;/servlet-name&gt; &lt;url-pattern&gt;/terms&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;servlet&gt; &lt;servlet-name&gt;info-privacy&lt;/servlet-name&gt; &lt;jsp-file&gt;/WEB-INF/jsp/info/privacy.jsp&lt;/jsp-file&gt; &lt;/servlet&gt; &lt;servlet-mapping&gt; &lt;servlet-name&gt;info-privacy&lt;/servlet-name&gt; &lt;url-pattern&gt;/privacy&lt;/url-pattern&gt; &lt;/servlet-mapping&gt; &lt;/web-app&gt; </code></pre> <p>The log printed by eclipse shows nothing. Just the 404. <strong>I found the problem will occur when I edit something and save the changes. Eclipse will auto reload the context and home page returns 404.</strong></p>
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    1. COWhat do you mean re-run? When does the 404 occur? Is this the only URL impacted?
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    2. COre-deploy, there is no obvious reason when it will occur, and yes only root url is impacted. I try to print something inside the root servlet and it's not executed. So it's never called.
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    3. COTo map to context root use `/` url-mapping.
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      1. USSotirios Delimanolis
 

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