java - Need help to understand spring config files -

i studying existing spring mvc 3 project, while looking spring , context config files confused, please clear or suggest me if wrong.

upadte root-context.xml file

<beans xmlns="http://www.springframework.org/schema/beans"     xmlns:xsi="http://www.w3.org/2001/xmlschema-instance"     xsi:schemalocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">      <!-- root context: defines shared resources visible other web components -->      <bean id="messagesource" class="org.springframework.context.support.reloadableresourcebundlemessagesource">         <property name="basenames">             <list>                 <value>classpath:messages</value>                </list>         </property>          <property name="defaultencoding" value="utf-8" />     </bean>      <bean id="localechangeinterceptor"         class="org.springframework.web.servlet.i18n.localechangeinterceptor">         <property name="paramname" value="lang" />     </bean>      <bean id="localeresolver"         class="org.springframework.web.servlet.i18n.cookielocaleresolver">         <property name="defaultlocale" value="en" />             </bean>      <bean id="themesource" class="org.springframework.ui.context.support.resourcebundlethemesource">         <property name="basenameprefix" value="detailtheme-" />     </bean>     <bean id="themeresolver" class="org.springframework.web.servlet.theme.cookiethemeresolver">         <property name="defaultthemename" value="en" />     </bean>   <!-- helper bean load properties files -->     <bean id="loadpropertiesfiles" class="org.commons.utilities.loadpropertiesfilehelper"         init-method="loadpropertiesfilemethod" lazy-init="false" /> </beans> 

here don't understand lang? understand it's veriable name value assigned paramname (default_param_name), don't understand how value assigned lang because don't find single location value (like en,hi..etc) set.

the confusing thing 1 more bean same class defined in servlet-context.xml :

<mvc:interceptors>         <beans:bean class="org.springframework.web.servlet.i18n.localechangeinterceptor">             <beans:property name="paramname" value="lang" />         </beans:bean> ... </mvc:interceptors> 

why two beans of same class defined, wrong? if not, work of bean defined in root-context.xml , servlet-context.xml?

below web.xml reference:

<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" version="2.5">   <context-param>     <param-name>contextconfiglocation</param-name>     <param-value>/web-inf/spring/root-context.xml</param-value>   </context-param>   <!-- listener prevent class loader leaks -->   <listener>      <listener-class>se.jiderhamn.classloader.leak.prevention.classloaderleakpreventor</listener-class>   </listener>     <listener>     <listener-class>org.springframework.web.context.contextloaderlistener</listener-class>   </listener>   <servlet>     <servlet-name>appservlet</servlet-name>     <servlet-class>org.springframework.web.servlet.dispatcherservlet</servlet-class>     <init-param>       <param-name>contextconfiglocation</param-name>       <param-value>/web-inf/spring/appservlet/servlet-context.xml</param-value>     </init-param>     <load-on-startup>1</load-on-startup>   </servlet>   <servlet-mapping>     <servlet-name>appservlet</servlet-name>     <url-pattern>/</url-pattern>   </servlet-mapping>       <filter>         <filter-name>characterencodingfilter</filter-name>         <filter-class>org.springframework.web.filter.characterencodingfilter</filter-class>         <init-param>             <param-name>encoding</param-name>             <param-value>utf-8</param-value>         </init-param>         <init-param>             <param-name>forceencoding</param-name>             <param-value>true</param-value>         </init-param>     </filter>       <filter-mapping>     <filter-name>characterencodingfilter</filter-name>     <url-pattern>/*</url-pattern>   </filter-mapping>   <filter>     <filter-name>sitemesh</filter-name>     <filter-class>org.sitemesh.config.configurablesitemeshfilter</filter-class>   </filter>   <filter-mapping>     <filter-name>sitemesh</filter-name>     <url-pattern>/*</url-pattern>   </filter-mapping>     <jsp-config>         <taglib>             <taglib-uri>/tagtld</taglib-uri>             <taglib-location>/resources/tld/enumtag.tld</taglib-location>         </taglib>     </jsp-config> </web-app> 

localechangeinterceptor intercept web requests web app, , query param name lang (e.g. http://mywebapp.com/login?lang=en), , try set app's locale accordingly can localization of web app.

as far 2 files root-context.xml , servlet-context.xml concerned - first file being used <listener-class>org.springframework.web.context.contextloaderlistener</listener-class> , second file being used org.springframework.web.servlet.dispatcherservlet.

contextloaderlistener can used initialize spring when not using spring mvc. dispatcherservlet specific spring mvc , needed if making use of it.

it may possible rid of root-context.xml, require review design of app there may non-springmvc components depend on beans defined root-context.xml.