Multiple application context, multiple dispatcher servlets?

Question

Until now I used to think that a web-application can have only one dispatcher-servlet which we define in web.xml

• Am I right in th

Answer 1

What is a situation we might need this in ?

^_OR
Advantages of multiple dispatcher servlets ^_OR
Why we need multiple dispatcher servlets?

Simple answer is to have DispatcherServlet's functionality in several forms

Dispatcher servlet functionality

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• Dispatcher Servlet uses HandlerMapping implementation to control the routing of requests to handler objects. Default is BeanNameUrlHandlerMapping and RequestMappingHandlerMapping.
• It's view resolution strategy can be specified via a ViewResolver implementation, resolving symbolic view names into View objects. Default is InternalResourceViewResolver.
• It's exception resolution strategy can be specified via a HandlerExceptionResolver, for example mapping certain exceptions to error pages.
• It's strategy for resolving multipart requests is determined by a MultipartResolver implementation.
• It's locale resolution strategy is determined by a LocaleResolver.
• It's theme resolution strategy is determined by a ThemeResolver.

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I will try to explain some of the functionalities provided by DispatcherServlet

Declaring Multiple dispatcher servlets
Consider we have two dispatcher servlets(DS) where DS1, DS2 are configured with different url patterns(**.simple, **.beanName) and they uses different dispatcher servlet configuration provided as given below.

DispatcherServlet     - simpleUrlHandlerDispatcherServlet
contextConfigLocation - /WEB-INF/simpleUrlHandlerMapping.xml
*.simple

DispatcherServlet     - beanNameUrlHandlerDispatcherServlet
contextConfigLocation - /WEB-INF/beanNameUrlHandlerMapping.xml
*.beanName

^{_{Advantage 1:}} We can have different HandlerMapping for different set of URL

DS1 bean name url handler mapping configuration

DS2 simple url handler mapping configuration

    
        
            simpleHello
            simpleHi
        
    

^{_{Advantage 2:}} We can have different view resolver for different set of URL's.

InternalResourceViewResolver for DS1
where it deals with only prefix + returned String + suffix.
TilesViewResolver for DS2
its implementation provided by apache tiles which is a layout/skeleton based plugin high level functionality as given below.
Or if we use TilesViewResolver with different layout for different set of URL's
anonymous user - different layout
logged in user - different layout

^{_{Advantage 3:}} We can have different theme resolver for different set of URL's.
These resolver continuously monitors cookie/session to resolve theme and serves stylesheet/theme qualified (as given in below image). Below given just an example for outcome of CookieThemeResolver.
Note: This is not about theme configuration but about theme resolver configuration.

^{_{Advantage 4:}} We can have different locale resolver for different set of URL's.
These resolver continuously monitors cookie/session/accept-header to resolve locale and loads application message qualified(as given in below image). Below given just an example for outcome of CookieLocaleResolver.
Note: This is not about locale configuration but about locale resolver configuration.