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Servlet not opening the welcome page [duplicate]

I have a confusion regarding the structure of the web.xml for the servlet mapping, I don't have any problem by executing it but I am trying to figure it how why we have such a pattern in the deployment descriptor.
<web-app>
<servlet>
<servlet-name>Servlet1</servlet-name>
<servlet-path>foo.Servlet</servlet-path>
</servlet>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/enroll</url-pattern>
</servlet-mapping>
</web-app>
Now as far as my understanding whenever a request is comes for url-pattern "/enroll", servlet container is going to match the servlet-name with the url-pattern and will try to find the corresponding servlet-path and will forward the control to foo.Servlet. so basically there would be two passes one for finding servlet-name and another for servlet-path, my question is if container is designed to work in the following way
<web-app>
<servlet>
<servlet-name>foo.Servlet</servlet-path>
<url-pattern>/enroll</url-pattern>
</servlet>
</web-app>
what would be the drawback if we use the following approach. Wouldn't that be more efficient and the response time would be fast.

It allows servlets to have multiple servlet mappings:
<servlet>
<servlet-name>Servlet1</servlet-name>
<servlet-path>foo.Servlet</servlet-path>
</servlet>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/enroll</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/pay</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/bill</url-pattern>
</servlet-mapping>
It allows filters to be mapped on the particular servlet:
<filter-mapping>
<filter-name>Filter1</filter-name>
<servlet-name>Servlet1</servlet-name>
</filter-mapping>
Your proposal would support neither of them. Note that the web.xml is read and parsed only once during application's startup, not on every HTTP request as you seem to think.
Since Servlet 3.0, there's the #WebServlet annotation which minimizes this boilerplate:
#WebServlet("/enroll")
public class Servlet1 extends HttpServlet {
See also:
How do servlets work? Instantiation, sessions, shared variables and multithreading
Difference between each instance of servlet and each thread of servlet in servlets?
Our Servlets wiki page

Jersey JAX-RS: Specifying /* as base URL pattern

I have a Dynamic Web application, and because of the requirements, I am specifying two types of servlet mappings in the web.xml file; Faces Servlet & Jersey(JAX-RS implementation).
My problem is, that if I try to use '/' as the base url-pattern in the Jersey configuration, then the resources of Faces Servlets stop working, i.e., nothing happens if I make REST call to those resources, otherwise everything works fine if I place something like'/rest/' in the Jersey Configuration. My web.xml file looks like this:
<!-- Jersey -->
<servlet>
<servlet-name>Jersey REST Service</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.saf.web.v2.beans</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Jersey REST Service</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
<!-- Faces Servlet -->
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>100</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
Is there a way to specify the Jersey mapping so there is nothing in the url-pattern but '/*' and Faces Servlet resources also work fine at the same time.
Thanks!

If you define that Jersey should serve all requests (this is what /* means) the Faces Servlet doesn't have a chance any more. So in general: There is no such way.
Maybe you could work around this be mapping Jersey to /rest and writing an own Servlet mapped to /* which dispatches to one of the other servlets. I would not recommend that.

I had the same problem but I fixed it by using
/rest/*
for jersey's servlet
and other part of application can have any other url-pattern, as in your case it is *.xhtml for JSF's servlet.

What is the use of <init-param> in web.xml regarding servlet?

What is the use of init-param tag? in web.xml reagarding servlet and jsp?
<servlet>
<servlet-name>sonoojaiswal</servlet-name>
<jsp-file>/welcome.jsp</jsp-file>
<init-param>
<param-name>dname</param-name>
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>sonoojaiswal</servlet-name>
<url-pattern>/welcome</url-pattern>
</servlet-mapping>
</web-app>

We can pass parameters to our servlet from the web.xml file using init param's. Here's a small example.
web.xml:
<servlet>
<description></description>
<display-name>Test</display-name>
<servlet-name>Test</servlet-name>
<servlet-class>servlets.Test</servlet-class>
<init-param>
<param-name>dname</param-name>
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Test</servlet-name>
<url-pattern>/Test</url-pattern>
</servlet-mapping>
Servlet:
PrintWriter printWriter = response.getWriter();
printWriter.println(getServletConfig().getInitParameter("dname"));
Output:
You will find an excellent answer by informatik01 on this subject here.

You can see that init-param is defined inside a servlet element. This means it is only available to the servlet under declaration and not to other parts of the web application.
You can use that particular parameter in only this Servlet not in others.
you can access it by ServletConfig object also
servletConfig.getInitParameter("dname");

They are called Servlet init parameters (defined in element)
Servlet init parameters are defined within the element for each specific servlet.
They are specific to each servlet.They are available in the init method of the servlet as arguments. this will be used for initial loading of values in the servlet.

How to serve static resources from a Vaadin/Spring application?

I have Vaadin web application with spring security integration for authentication. The configuration of the Vaadin servlet is pretty simple:
<servlet>
<servlet-name>Vaadin Application Servlet</servlet-name>
<servlet-class>com.example.SpringApplicationServlet</servlet-class>
<init-param>
<param-name>applicationBean</param-name>
<param-value>mainApplication</param-value>
</init-param>
<init-param>
<param-name>widgetset</param-name>
<param-value>com.example.widgetset.CustomWidgetSet</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Vaadin Application Servlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
The servlet initializes the Spring Context and returns the Vaadin application. I have also configured the security for that and have a custom login form configured like this:
<servlet>
<servlet-name>login</servlet-name>
<jsp-file>/jsp/login.jsp</jsp-file>
</servlet>
<servlet-mapping>
<servlet-name>login</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>login_error</servlet-name>
<jsp-file>/jsp/loginError.jsp</jsp-file>
</servlet>
<servlet-mapping>
<servlet-name>login_error</servlet-name>
<url-pattern>/login_error</url-pattern>
</servlet-mapping>
The login form is styled with an external css and there are also some images. Basically the images are located in /jsp/img and the stylesheet in /jsp/login.css. So the WAR structure looks like:
/jsp
/META-INF
/VAADIN
/WEB-INF
Neither the images nor the css gets loaded, because obviously all those requests are mapped to the vaadin servlet. How can I define some static resources directory, which wouldn't be served by the Vaadin servlet? I have tried the spring mvc:resources but that didn't work. Thank you for your help.
Bye,
Filip
I have figured this out. Although it is rather a workaround. I have mapped the Vaadin Application Servlet to something like /app/* instead of to /* (Remember that in this case you also have to map the same servlet to /VAADIN/*). With this configuration I am able to access the jsp directory from my webapp and everything works fine. I have deleted the whole Spring Resources configuration, as this just didn't work.
So once more, I am still pretty not pretty comfortable with this solution and would rather have my RESOURCES dir configured other way, but the client is happy :). If anyone has got the right solution I would appreciate to read it.

Use a url rewrite filter to get more contro on url mapping.
<filter>
<filter-name>UrlRewriteFilter</filter-name>
<filter-class>org.tuckey.web.filters.urlrewrite.UrlRewriteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>UrlRewriteFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
then map Vaadin application to /vaadin for example and configure url maping in urlrewrite.xml
<rule>
<from>/styles/**</from>
<to last="true">/styles/$1</to>
</rule>
<rule>
<from>/images/**</from>
<to last="true">/images/$1</to>
</rule>
<rule>
<from>/**</from>
<to>/vaadin/$1</to>
</rule>
<outbound-rule>
<from>/vaadin/**</from>
<to>/$1</to>
</outbound-rule>
EDIT
Other option is put static files in /VAADIN/ directory.

I have figured this out. Although it is rather a workaround. I have mapped the Vaadin Application Servlet to something like /app/* instead of to /* (Remember that in this case you also have to map the same servlet to /VAADIN/*). With this configuration I am able to access the jsp directory from my webapp and everything works fine. I have deleted the whole Spring Resources configuration, as this just didn't work.
So once more, I am still pretty not pretty comfortable with this solution and would rather have my RESOURCES dir configured other way, but the c

Might be late but for who is still having problems with serving static content while using vaadin /* mapping, the solution I found was using apache's default servlet org.apache.catalina.servlets.DefaultServlet, so a web.xml will have something like:
<?xml version="1.0" encoding="UTF-8"?>
<web-app
id="WebApp_ID" version="3.0" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<servlet>
<servlet-name>myservlet</servlet-name>
<servlet-class>com.vaadin.server.VaadinServlet</servlet-class>
<init-param>
<param-name>UI</param-name>
<param-value>com.ex.myprj.MyUI</param-value>
</init-param>
<!-- If not using the default widget set-->
<init-param>
<param-name>widgetset</param-name>
<param-value>com.ex.myprj.AppWidgetSet</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>myservlet</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>Static content Servlet</servlet-name>
<servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>listings</param-name>
<param-value>false</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Static content Servlet</servlet-name>
<url-pattern>/customer/*</url-pattern>
</servlet-mapping>
</web-app>
So in the example above, despite having vaadin at /*, the /customer/* part will be served as static content by the DefaultServlet

Servlet Mapping using web.xml

I have a confusion regarding the structure of the web.xml for the servlet mapping, I don't have any problem by executing it but I am trying to figure it how why we have such a pattern in the deployment descriptor.
<web-app>
<servlet>
<servlet-name>Servlet1</servlet-name>
<servlet-path>foo.Servlet</servlet-path>
</servlet>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/enroll</url-pattern>
</servlet-mapping>
</web-app>
Now as far as my understanding whenever a request is comes for url-pattern "/enroll", servlet container is going to match the servlet-name with the url-pattern and will try to find the corresponding servlet-path and will forward the control to foo.Servlet. so basically there would be two passes one for finding servlet-name and another for servlet-path, my question is if container is designed to work in the following way
<web-app>
<servlet>
<servlet-name>foo.Servlet</servlet-path>
<url-pattern>/enroll</url-pattern>
</servlet>
</web-app>
what would be the drawback if we use the following approach. Wouldn't that be more efficient and the response time would be fast.

It allows servlets to have multiple servlet mappings:
<servlet>
<servlet-name>Servlet1</servlet-name>
<servlet-path>foo.Servlet</servlet-path>
</servlet>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/enroll</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/pay</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Servlet1</servlet-name>
<url-pattern>/bill</url-pattern>
</servlet-mapping>
It allows filters to be mapped on the particular servlet:
<filter-mapping>
<filter-name>Filter1</filter-name>
<servlet-name>Servlet1</servlet-name>
</filter-mapping>
Your proposal would support neither of them. Note that the web.xml is read and parsed only once during application's startup, not on every HTTP request as you seem to think.
Since Servlet 3.0, there's the #WebServlet annotation which minimizes this boilerplate:
#WebServlet("/enroll")
public class Servlet1 extends HttpServlet {
See also:
How do servlets work? Instantiation, sessions, shared variables and multithreading
Difference between each instance of servlet and each thread of servlet in servlets?
Our Servlets wiki page