Adding missed servlet mapping file for java demo website landing page. (#2841)

java/demo/src/main/webapp/WEB-INF/web.xml

@@ -19,7 +19,8 @@
     <servlet-name>Input</servlet-name>
     <url-pattern>/inputform</url-pattern>
   </servlet-mapping>
-  <welcome-file-list>
-    <welcome-file>Input</welcome-file>
-  </welcome-file-list>
+  <servlet-mapping>
+    <servlet-name>Input</servlet-name>
+    <url-pattern>/</url-pattern>
+  </servlet-mapping>
 </web-app>