每当我添加新的servlet时Tomcat就会停止工作

Question

I'm working on a web app project on eclipse.
I have a weird problem: Every time i try to add a new servlet to my project, when i try to run tomcat I get this error:

Server Tomcat v7.0 Server at localhost failed to start.

and I'm no more able to run my project.

this is my web.xml file

<?xml version="1.0" encoding="UTF-8"?>
<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_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Jeans4</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>

  <servlet>
    <description></description>
    <display-name>prova</display-name>
    <servlet-name>prova</servlet-name>
    <servlet-class>Jeans.prova</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>prova</servlet-name>
    <url-pattern>/prova</url-pattern>
  </servlet-mapping>

  <servlet>
    <description></description>
    <display-name>FileUploadDBServlet</display-name>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>Jeans.FileUploadDBServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <url-pattern>/FileUploadDBServlet</url-pattern>
  </servlet-mapping>

  <servlet>
    <description></description>
    <display-name>BlobDisplay</display-name>
    <servlet-name>BlobDisplay</servlet-name>
    <servlet-class>Jeans.BlobDisplay</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobDisplay</servlet-name>
    <url-pattern>/BlobDisplay</url-pattern>
  </servlet-mapping>



</web-app>

if i delete all my servlet tags this way:

<?xml version="1.0" encoding="UTF-8"?>
<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.coma/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Jeans4</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list> 
</web-app>

tomcat works and doens't give me that error.

Answer 1

Either an instance of tomcat is already running (and the 2nd instance can not run due to ports already in use), or there is some error in your configuration preventing tomcat from starting. You need to look at the tomcat logs to determine the reason. See "<tomcat_dir>/logs/ "

Answer 2

Once I had the same issue and it turned out that I forgot to include / in the url pattern for my servlet. So if you are using annotations for some of your servlets and, for example, you have one of your servlets annotated like this @WebServlet("MyServletSessionContext") instead of @WebServlet("/MyServletSessionContext") and try to deploy it and restart tomcat you will get this error. Make sure that you have / for all your urlPatterns