I am trying to follow this example
but I can't understand this part:
Imagine also that the servlet's context path is myServer/myApp/servlets. The servlet container would direct a request with URL myServer/myApp/createUser.do myServlet to myServlet, because the request URL matches the pattern *.do. Servlet myServlet can extract the requested operation's name from the request URL.
I can't understand the request, shouldn't it be myServer/myApp/myServlet/createUser.do? And how can one create such a request? Can I just put myServlet/createUser.do in the action of a form?
Thank you for your time.
Iulia
No, you create a mapping to your servlet for myapp. The servlet name itself usually never shows in the request URL. So every request that goes to myapp will be redirected to your servlet if it matches. That means that your mapping
http://myserver/myapp/*.do
redirects every request with a .do to your servlet. Now the servlet has to deal with the request URL (e.g. render the view for createUser)
Related
How can I log all requests in Spring MVC, even the resource not founds ones?
I guess interceptors can not log resource not found requests. What do you suggest?
Have you tried using implementation of javax.servlet.Filter?
Filter in contrary to Spring's interceptor is part of a Java's standard and is executed by the servlet container for each incoming HTTP request..
Spring MVC use exactly one servlet and that is DispatcherServlet which, as the name suggest, disptach received request to correct controller which process the request futher.
Spring even provide few concrete implementations of Filter that can log incoming request for you such as: CommonsRequestLoggingFilter or ServletContextRequestLoggingFilter.
You can choose one of the above implementations or implement Filter interface by yourself - whatever you decide, by using Filter you should be able to log every single request received by your servlet container.
How do we handle incoming request to a wrong contextpath in spring mvc?
I have deployed a spring mvc application having contextpath as
http://exampledomain.com/mycontext
But when I try accessing url http://exampledomain.com/wrongcontext I get error as HTTP Status 404 - /wrongcontext/
I have implemented error handling which works fine for all wrong url when correct context path is used but it does not work for wrong context path.
I am trying to understand how do we redirect all incoming request to specific page in production environment..
thanks in advance
Your application can only see requests to its context /mycontext There is nothing your application can do about requests to other contexts.
You can however deploy an application at the root context / and implement an error handler there.
Check out this answer: How to customize JBoss AS7 404 page
That answer relates to JBoss, but the same idea will apply on other servers.
It is not possible to handle wrong context path requests in Spring since it only will handle the requests which goes to your context root. You have to take a look at server configuration parameters to redirect those kind of requests. If you are working on Tomcat, check path parameter of context.xml:
https://tomcat.apache.org/tomcat-7.0-doc/config/context.html#Defining_a_context
We can use #ExceptionHandler inside a #Controller or #ControllerAdvice to handle such kind of exceptions and decide on the view page to be rendered.
#ExceptionHandler({ HttpRequestMethodNotSupportedException.class,
HttpMediaTypeNotSupportedException.class, HttpMediaTypeNotAcceptableException.class,
MissingPathVariableException.class, MissingServletRequestParameterException.class,
ServletRequestBindingException.class,MethodArgumentNotValidException.class, MissingServletRequestPartException.class,
NoHandlerFoundException.class})
public ModelAndView handleException(){
return new ModelAndView("errorpage");
}
Would like to know how many instances of dispatcher servlet is created in a real time environment.
When there are multiple requests coming to the application, and if spring creates singleton objects how does one object handles multiple requests?
What happens when there are so many people accessing the website and since dispatcherServlet object is only one and all requests are handled by same object, won't it create any performance issue?
As M. Deinum says, one servlet to rule them all. I'll try to provide a very general description of the ServletDispatcher life cycle.
When the request leaves the browser it carries with it information from the user. This goes to the DispatcherServlet the front controller which is the single servlet that delegates requests to other components.
DispatcherServlet's job is to send the request to the right controller. Since a application can have many controllers DispatcherServlets get the help to decide which one to send it to by consulting the handler mapping
The DispatcherServlet sends the request to the destination controller,
The controller packs up the model-data and identifies the name of the view that is showing the output and sends this back to the dispatcherservlet.
DispatcherServlet consults with the viewResolver and looks up the view that is set to display the data.
The view is implemented (by a JSP for example) by using the model data to generate output. Which is sent back to the client.
This all happens very fast (ms) which means that thousands of requests can be handled in a very short time.
I have a servlet that responds to a URL and then forwards to a JSP in a typical MVC pattern.
Many pages share the same page head so in the JSP there is an include to head.jsp
head.jsp is placed inside WEB-INF so that it cannot be accessed directly.
Now I find that I need to add some control to the head. Rather than forwarding to WEB-INF/head.jsp and putting scriptlets in I would like to forward to a servlet instead.
How can I forward from the JSP to a servlet without mapping that servlet to a URL as I do not want to give direct access to this servlet.
Or to put it another way is there a servlet equivalent of WEB-INF to hide it from direct access? So the servlet can only be called via an include?
Rather than forwarding to WEB-INF/head.jsp and putting scriptlets in I would like to forward to a servlet instead.
It's indeed possible to do this (using <jsp:include> or a small scriptlet that dispatches), but I'm not sure whether this is really the best approach. The Servlet would either write directly to the response or would put some data in the request scope that the JSP can pick up later.
Writing directly to the response is a bit debatable today and for the other approach you don't need a Servlet at all.
The idiomatic way is to use some helper bean that contains the logic. The original Servlet you mentioned can put this bean into request scope, or you can use the <jsp:usebean> tag. Reference the data the helper bean prepared via expression language or very simple scriptlets.
So the servlet can only be called via an include?
If you still want to go this route, there might be an option of securing the Servlet behind a role and then giving the head.jsp a run-as role in web.xml:
<servlet>
<servlet-name>headInclude</servlet-name>
<jsp-file>/WEB-INF/head.jsp</jsp-file>
<run-as>
<role-name>SYSTEM</role-name>
</run-as>
</servlet>
disclaimer: I have never tried this myself, just pointing in a possible direction.
I'm creating a Spring MVC application that will have a controller with 'RequestMapping'-annotated methods, including a JSON method. It currently has static content that resides in webapps/static, and the app itself resides in webapps/myapp. I assume that Catalina's default servlet is handling the static content, and my *.htm url-pattern in web.xml is returning the request for my JSP page, but I haven't been able to get the JSON method to be called. How do I write the url-pattern in the servlet mapping to do so? Using /* has not worked; it prevents the app from being accessed at all. Is there anything else to be aware of?
I've learned of the default url-pattern, '/', which appears to be a match for my JSON request.