What type of information should be present in the dispatcher-servlet.xml and applicationContext.xml?
The applicationContext.xml is loaded by the ContextLoadeListener and should contain your shared/global beans. Things like the datasource, jms connecetionfactories, services, repositories etc.
Your dispatcher-servlet.xml is loaded by the DispatcherServlet and should contain only web related things like controllers, viewresolvers, exceptionhandlers etc.
This is a general rule of thumb of course.
Related
What is the difference between DispatcherServlet and ContextLoaderListener in Spring framework? Do we need to configure both of them in web.xml when we are using spring framework?
AFAIK each DispatcherServlet will have a WebApplicationContext. By default the DispatcherServlet looks for a spring configuration file named [appname]-servlet.xml under WEB-INF folder.
Do we need to configure DispatcherServlet?
Yes, every spring application should configure DispatcherServlet as it is the one through which all the requests are routed. It decides the appropriate method of the controller class to handle the request. Once controller returns the model along with the logical view, DispatcherServlet takes the help of ViewResolver to resolve the view (generally JSPs) and will pass the model data to the view, which is finally rendered on the browser.
Do we need to configure ContextLoaderListener?
No, this is not mandatory. Spring applications can live with out ContextLoaderListener.
Why do we need ContextLoaderListener?
Usually when we build multi-tier applications we don't want to clutter all the beans in one config file [appname]-servlet.xml. For example if you configure spring security you wanted to include all those beans in security-context.xml, in the same way all the beans belonging to service layer are configured in applicationContext.xml and some would like to configure beans belonging to DAO layer in dao-context.xml. So when you configure all these beans in different context files, you need to let know spring that these files exist as spring only knows about [appname]-servlet.xml. ContextLoaderListener will help spring recognize all the other context files.
Hope this helps!
The root WebApplicationContext is a Spring Application Context shared across the application.
A DispatcherServlet instance actually has its own
WebApplicationContext.
One can have multiple DispatcherServlet instances in an application, and each will have its own WebApplicationContext.
The root WebApplicationContext is shared across
the application, so if you have a root WebApplicationContext and
multiple DispatcherServlets, the DispatcherServlets will share the
root WebApplicationContext.
However, for a simple Spring MVC application, one can even have a situation where there is no need to have a root WebApplicationContext. A DispatcherServlet would still have its own WebApplicationContext, but it doesn’t actually need to have a parent root WebApplicationContext.
So, which beans should go in the root Web Application Context and which beans should go in the DispatcherServlet’s Web Application Context?
Well, general beans such as services and DAOs make their way in root Web Application Context, and more web-specific beans such as controllers are included in DispatcherServlet’s Web Application Context.
When DispatcherServlet starts up, it creates a Spring application context and starts
loading it with beans declared in the configuration files or classes that it’s given.
But in Spring web applications, there’s often another application context. This
other application context is created by ContextLoaderListener
Whereas DispatcherServlet is expected to load beans containing web components
such as controllers, view resolvers, and handler mappings, ContextLoaderListener is
expected to load the other beans in your application. These beans are typically the
middle-tier and data-tier components that drive the back end of the application.
Good luck!
I start to learn spring recently.
My goal is to use spring MVC to do restful api
I know spring MVC is web framework in spring
I know that in spring,there is beans.xml
And in spring MVC , there is servletname-servlet.xml
I want to know where is difference??
Is it means if I use spring MVC,I don't need to use beans.xml??
Please give me some way or give me example project link with spring and spring MVC together
The servletname-servlet.xml defines the beans for one servlet's app context. There can be number of servlets in a webapp and for every servlet we have servletname-servlet.xml (e.g. spring1-servlet.xml for servlet1, spring2-servlet.xml for servlet2).
Beans defined in servletname-servlet.xml can reference beans in beans.xml, but not vice versa.
All Spring MVC controllers must go in the servletname-servlet.xml context.
Beans.xml contain beans that are shared between all servlets in a webapp.Usually the beans.xml context is not necessary if you have only one servlet in your webapp.
You could define all your beans in servletname-servlet.xml but it's not a good practice.
Usually if you create a web application in 'pure' spring (ie. without spring MVC) then you will add ContextLoaderListener as a filter to your web.xml. Then spring will look for applicationContext.xml when you will usually import beans.xml.
In servletname-servlet.xml you define servlets. Servlets can refer other beans. So it's good practice to separate front (servlets) from backend (beans.xml).
Also remember that beans declared in servletname-servlet.xml are overriding the definitions of any beans defined with the same name in the global scope.
See also better answer at: ContextLoaderListener or not?
I created a simple spring-web-mvc project based on maven. The sample includes two configuration files. One in src / main / resources / spring / application-config.xml
and a second in src / main / webapp / WEB-INF / mvc-config.xml
Is that config normal? I think it is just configuration splitting basics mvc stuff in mvc-config.xml and application-config.xml for spring commons or?
For a web application then that is fairly normal - although the naming convention for the two files is often dispatcher-servlet.xml and applicationContext.xml.
The dispatcher-servlet.xml (or mvc-config.xml as in your question) is the configuration file for the web application context and contains the web specific beans and configuration for Spring MVC. It is loaded by the DispatcherServlet when the application starts up.
The applicationContext.xml (or application-config.xml as in your question) is the configuration file for the main Spring application context and contains the non-web business beans (typically services, DAOs etc). This file is often spilt into fragments - with a fragment containing the beans for each logical layer within the app. This file is typically loaded by the ContextLoaderListener defined in the web.xml.
Spring automatically sets the main application context as the parent of the web application context. This ensures that web components (such as controllers) have access to business beans in the application context. However, business beans are not able to see beans in the web application context.
In my project, we have a spring mvc application.
It has got both applicationcontext.xml as well as -servlet.xml config files.
Bean definitons are spread in both the files.
I want to know when we have -servlet.xml wats the need for applicationcontext.xml?
Please provide any explanation in this area.
applicationContext.xml will have the bean definitions of the core spring components.
project-servlet.xml will have bean definitions of indivisual servlets.
-servlet.xml can have references to applicationContext.xml not the other way round.
What you refer as applicationContext.xml is the root application context (you put beans there when you need application-wide access to them) and what you refer as the [servlet]-context.xml is a specific Spring Bean configuration xml for Spring MVC's DispatcherServlet.
servlet-context is specific to a servlet and application context is shared for whole application. So when you define a Bean in servlet-context.xml the Bean is available to the context of that specific servlet, but when you define a Bean in application-context.xml it is available in the whole application. So if you have multiple dispatcherServlet you can have separate servlet-context for each servlet. But there is only one application-context for the application
Where to put application level beans in Spring MVC? Into root-context.xml or into servlet-context.xml?
Beans declared in root-context.xml (services) are visible for beans in servlet-context.xml (controllers), but not the other way around. Therefore there can be a dependency from controllers to services, but the reverse dependency is forbidden by Spring.
That being said put MVC-independent code (services, DAOs, etc.) in main context and put web-only stuff in servlet context.