WHAT IS WEB.XML FILE

WHAT IS WEB.XML FILE 

PART 1

Most of the dynamic web projects contains dynamic web x ml files to define your projects (big picture). Some of them has this file contents as annotations.

For example the default one is

<?xml version="1.0" encoding="UTF-8"?>

<web-app id="WebApp_ID" version="2.4" 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/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

       <display-name>DynamicWebExample</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>

    In the first row the x ml version is defined. This x ml version and encoding type is related with the web x ml own not for the project.

    Root of the web x ml file is the <web-app that has id, version and namespaces.

    <displayName> is the name of your project.

    <welcome-file-list> tag includes one or more <welcome-file> tags which contain some files related with welcome. If you want to reach to the project with the project name url such as http:/localhost:8080/DynamicWebExample you can see the welcome file. If there is not a welcome file in project that was defined in web.xml file, web.xml file gives the another one from the order to project so the files in welcome-file-list is processed in the order of the list. If you type as http:/localhost:8080/DynamicWebExample then you can see the picture 2.

Picture 1

Picture 2

The other property that i will explain is the <jsp-property>

<jsp-config>

              <jsp-property-group>

                     <description>To Encode With Utf8</description>

                     <url-pattern>index*.jsp</url-pattern>

                     <page-encoding>UTF-8</page-encoding>

              </jsp-property-group>

</jsp-config>

    If you want to make some pages encoding specialized you can use this method. For example the code above forces the user to encode index,index1,indexa,indexq… etc files in UTF-8 so if you encode this files different from this encoding type you will get error while testing such as :

org.apache.jasper.JasperException: /index.jsp(1,1) Page-encoding specified in jsp-property-group (UTF-8) is different from t…

This error causes from the jsp that was defined as : 

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding= "ISO-8859-1"%>

    so if you change the pageEncoding to UTF-8 then you can test it correctly. But now the utf characters will come as iso type and such as ? so if you change also the charset to UTF-8 you can see the page correctly typed. Such as for the Swedish characters WELCOME ö now you can test.

       If you can not see your own characters even after changing the encoding you can change your tomcat language that I will explain how to do this later.

    You can also avoid your errors from user with this code

<error-page>

       <exception-type>java.lang.ClassNotFoundException</exception-type>

       <location>/hello.jsp</location>

</error-page>

    If you encounter with the exception type that is class is not in the project or not on the path is given, you can route your web to specialized files.

<error-page>

       <error-code>404</error-code>

       <location>/hello.jsp</location>

</error-page>

You can also code such as above. This is not the same with the first one(!).

<icon>

              <large-icon></large-icon>

</icon>

You can also define your application icon with the code above.

Configuration tags will continue…