The welcome files mechanism allows you to specify a list of files that the web container will use for appending to a request for a URL (called a valid partial request) that is not mapped to a web component.
For example, suppose you define a welcome file welcome.html. When a client requests a URL such as host:port/webapp/directory, where directory is not mapped to a servlet or JSP page, the file host:port/webapp/directory/welcome.html is returned to the client.
If a web container receives a valid partial request, the web container examines the welcome file list and appends to the partial request each welcome file in the order specified and checks whether a static resource or servlet in the WAR is mapped to that request URL. The web container then sends the request to the first resource in the WAR that matches.
If no welcome file is specified, the Application Server will use a file named index.XXX, where XXX can be html or jsp, as the default welcome file. If there is no welcome file and no file named index.XXX, the Application Server returns a directory listing.
To specify a welcome file in the web application deployment descriptor using NetBeans IDE, do the following:
Open the project if you haven’t already.
Expand the project’s node in the Projects pane.
Expand the Web Pages node and then the WEB-INF node.
Do one of the following, making sure that the JSP pages you specify are actually included in the WAR file:
Click Pages at the top of the editor pane and enter the names of the JSP pages that act as welcome files in the Welcome Files field.
Click XML at the top of the editor pane, specify the JSP pages using welcome-file elements and include these elements inside a welcome-file-list element. The welcome-file element defines the JSP page to be used as the welcome page.
The example discussed in Encapsulating Reusable Content Using Tag Files has a welcome file.