As mentioned above, it's a handler's responsibility to provide a ModelAndView
instance. A typical ModelAndView holds one or more named model beans. It also
contains a view name (such as "rss") or, alternatively, a view
implementation (of type org.springframework.web.servlet.View).
While building the model to be rendered by the CAE view dispatcher (see below) it is necessary
to consider the following: At least a model bean with the name "self" needs to be
added to the ModelAndView. This bean represents the "main" or "root" object of
the model and will be the used for looking up an adequate view. In addition, no View instance
must be added to the ModelAndView because such an instance will be resolved
automatically by the view resolving mechanism based on the type of the "self" bean in
conjunction with the view name.
CoreMedia provides some convenience functions in
com.coremedia.objectserver.web.HandlerHelper for building an adequate
ModelAndView.
HandlerHelper.createModel(Object bean): Creates an instance with the given bean as the "self" object.HandlerHelper.createModelWithView(Object bean, String viewName): Creates an instance with the given bean as the "self" object and a specific view name.
There are situations where a request must not result in a rendered page but should be answered
with a special HTTP response code. E.g. a "bad request" (Status: 400) response should be
returned in case that the request is malformed or a "not found" in case that the requested
resource does not exist. Instead of sending such responses directly by using
HttpServletResponse, it is also possible to return a ModelAndView
containing a com.coremedia.objectserver.web.HttpError bean. The advantage of this
approach is to let the view rendering decide how to handle a response like this. One way would
be to use the programmed view (see below)
com.coremedia.objectserver.view.HttpErrorView for writing the HTTP error to the
response. Another approach is to render a comprehensive error page instead by using a template
com.coremedia.objectserver.view/HttpError.jsp. The HandlerHelper utility provides
helper methods for dealing with such situations:
HandlerHelper.notFound(): Provides aModelAndViewthat contains anHttpErrorwith code404.HandlerHelper.badRequest(): Provides aModelAndViewthat contains anHttpErrorwith code400.
Finally, a handler might decide not to render a bean directly but send a "temporarily moved" response (Status: 302) instead. This is a typical use case when dealing with POST requests: After updating the application state, the user's web browser is redirected to a result page. This case is also supported by the HandlerHelper:
HandlerHelper.redirectTo(Object bean): Redirect to a page that is represented by the given bean. See Section 4.3.2, “Building Links” for further information.
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