I am wondering what are the requirements for a method (or a class) to be labeled with #Controller? As for input arguments, the Spring tutorial seems to indicate that methods can sometimes take in nothing and sometimes take in a Model object:
http://blog.springsource.com/2011/01/04/green-beans-getting-started-with-spring-mvc/
And this:
Spring MVC Controllers Return Type
seems to indicate that the return type can be a String or a ModelAndView. I tried to look that up in the official documentation but couldn't find much info. I presume there must be some requirements. Any pointers?
In Spring Class is marked as #Controller, methods are marked as #RequestMapping handling specific request based on parameter,url path, accept header etc.
Spring MVC is highly flexible and allows you to have many return types see spring reference see "Supported method return types" section on the same page.
Also spring-mvc-3-showcase blog
Related
I have a Controller with the following method:
#RequestMapping(method = POST)
public ModelAndView emailRegister(EmailParameter parameters, ModelMap model) {}
Where EmailParameter is an interface. I understand Spring (magically?) maps the incoming HTTP parameters to my object fields by name, and it can't do this as I have declared an Interface.
Is it possible to declare an interface here, if so is there additional config I need somewhere?
I don't have extensive programming experience so I may be wrong in trying to use an Interface type here, but I believe this is what I should be doing?
Additionally if someone could explain how Spring maps the request parameters to my object fields, that would be much appreciated. Or a link to where this is explained, as I haven't been able to find one!
Thanks
You shouldn't use Interface because Spring needs to instantiate that object, otherwise you will be requiring the property editors OR converters.
Read the following post to know about How Spring MVC Binds Parameter?
Read section "Binding Domain Object" in following link.
https://web.archive.org/web/20160516151809/http://www.jpalace.org/document/92/binding-and-validation-of-handler-parameters-in-spring-mvc-controllers
I am new to spring framework. Even I dont have any deep concept about annotation.
I am developing a very small application using spring mvc 3 framework and also I used annotation.
I have a confusion. I have one spring-servlet.xml. Here I have not defined any handler mapping. But still it is working. So must be there some default handler mapping. Can you please let me what is this default handler mapping and how I can override it so that I do some customization.
It is all explained in: http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/mvc.html#mvc-config
Also see this question: How to use default-servlet-handler and Where to put default-servlet-handler in Spring MVC configuration
Spring 3.1 and later doesnt need DefaultAnnotationHandlerMapping and AnnotationMethodHandlerAdapter declaration in the [servelt-name]-servlet.xml
These links might help:
Spring Controller to handle all requests not matched by other Controllers
https://dzone.com/articles/using-the-spring-requestmapping-annotation
I had the same problem that I just resolved so I have confirmed the approach below works, although this is with annotations rather than an XML configuration.
You specify URL prefixes at the controller class level and include a request mapping annotation for ** to ensure you match on anything that falls through your other handlers for this class. There's really nothing special or default about this handler other than the fact that you're defining a handler that is guaranteed to match everything under the class level mappings.
Note: This is not magic. Your handlers are still subject to Spring's ordering algorithm regarding the "best match". It would be nice to have an annotation providing for a true default when nothing else matches handler, especially in cases with complex mappings where "**" is useful outside of this catch-all handler. The basic implementation is:
#RestController
#RequestMapping(value={"/path1/","/path2/"})
public class MyRestController {
#RequestMapping("/subpath")
String matchedRequestHandler () {
return "This matches /path1/subpath and /path2/subpath.";
}
#RequestMapping("**")
String unmatchedRequestsHandler () {
return "This matches everything else.";
}
}
In my actual use case, I needed to handle arbitrary paths to resources inside of the URL pattern and therefore needed to support a variable number of directories. Ideally, that would be handled using a pattern such as:
"/base/{optionaldir}/**/{entityName}/{describeVar:describe.json}"
which works fine by itself, but it isn't compatible with a default handler bound to "**" since the "**" mapping is calculated by Spring as a better match for these types of requests.
Instead, I had to add a bunch of separate entries to my request mapping to support the arbitrary paths within the URL pattern, e.g.
value={"/base/{optionaldir}/{entityName}/{describeVar:describe.json}",
"/base/{optionaldir}/*/{entityName}/{describeVar:describe.json}",
"/base/{optionaldir}/*/*/{entityName}/{describeVar:describe.json}",
"/base/{optionaldir}/*/*/*/{entityName}/{describeVar:describe.json}"
}
Alternatively, I could have handled everything with a "**" mapping and parsed the URL myself, but that kind of defeats the purpose of using request mappings with path variables. Hopefully Spring's capabilities will evolve in this area in the future.
Scenario: I have a web application that uses Spring 3 MVC. Using the powerful new annotations in Spring 3 (#Controller, #ResponseBody etc), I have written some domain objects with #XML annotations for marhalling ajax calls to web clients. Everything works great. I declared my Controller class to have a return type #ResponseBody with root XML object - the payload gets marshalled correctly and sent to Client.
The problem is that some data in the content is breaking the XML compliance. I need to wrap this with CDATA when necessary. I saw a POST here How to generate CDATA block using JAXB? that recommends using a custom Content Handler. Ok, fantastic!
public class CDataContentHandler extends (SAXHandler|XMLSerializer|Other...) {
// see http://www.w3.org/TR/xml/#syntax
private static final Pattern XML_CHARS = Pattern.compile("[<>&]");
public void characters(char[] ch, int start, int length) throws SAXException {
boolean useCData = XML_CHARS.matcher(new String(c,start,length)).find();
if (useCData) super.startCDATA();
super.characters(ch, start, length);
if (useCData) super.endCDATA();
}
}
Using Spring MVC 3, how do I achieve this? Everything was "auto-magically" done for me with regards to the JAXB aspects of setup, Spring read the return type of the method, saw the annotations of the return type and picked up JAXB2 off the classpath to do the marshalling (Object to XML conversion). So where on earth is the "hook" that permits a user to register a custom Content Handler to the config?
Using EclipseLink JAXB implementation it is as easy as adding #XmlCDATA to the Object attribute concerned. Is there some smart way Spring can help out here / abstract this problem away into a minor configuration detail?
I know Spring isn't tied to any particular implementation but for the sake of this question, please can we assume I am using whatever the default implementation is. I tried the Docs here http://static.springsource.org/spring-ws/site/reference/html/oxm.html but it barely helped at all with this question from what I could understand.
Thanks all for any replies, be really appreciated.
Update:
Thanks for the suggested answer below Akshay. It was sufficient to put me on right tracks. Investigating further, I see there is a bit of history with this one between Spring version 3.05 and 3.2. In Spring 3.05 it used to be quite difficult to register a custom MessageConverter (this is really the goal here).
This conversation pretty much explains the thinking behind the development changes requested:
https://jira.springsource.org/browse/SPR-7504
Here is a link to the typically required class override to build a cusom solution:
http://static.springsource.org/spring/docs/3.1.0.M1/javadoc-api/org/springframework/http/converter/AbstractHttpMessageConverter.html
And the following Question on stack overflow is very similar to what I was asking for (except the #ResponseBody discussion relates to JSON and jackson) - the goal is basically the same.
Spring 3.2 and Jackson 2: add custom object mapper
So it looks like usage of , and overriding MarshallingHttpMessageConverter is needed, registering to AnnotationMethodHandlerAdapter. There is a recommended solution in link above to also get clever with this stuff and wrap the whole thing behind a custom defined Annotation.
I haven't yet developed a working solution but since I asked the questions, wanted to at least post something that may help others with the same sort of question, to get started. With all due respect, although this has all improved in Spring 3.2, it's still bit of a dogs dinner to get a little customization working... I really was expecting a one liner config change etc.
Rather than twist and bend Spring, perhaps the easiest answer for my particular issue is just to change JAXB2 implementation and use something like Eclipse Link JAXB that can do this out of the box.
Basically you need to create a custom HttpMessageConverter. Instead of relying on the Jaxb2RootElementHttpMessageConverter that spring uses by default.
Unfortunately, customizing one converter means you are telling spring that you will take care of loading all the converters you need! Which is fairly involved and can get complicated, based on whether you use annotations, component scanning, Spring 3.1 or earlier, etc.. The issue of how to add a custom converter is addressed here: Custom HttpMessageConverter with #ResponseBody to do Json things
In your custom message converter you are free to use any custom JAXB2 content handlers.
Another, simpler approach to solve your original problem would be to use a custom XmlJavaTypeAdapter. Create a custom implementation of javax.xml.bind.annotation.adapters.XmlAdapter to handle CDATA, in the marshal method wrap the return value with the cdata braces. Then in your mapped pojo, use the XmlAdapter annotation, pass it the class of your custom adapter and you should be done.
I have not myself implemented the adapter approach, so couldn't provide sample code. But it should work, and won't be a lot of work.
Hope this helps.
With Spring, how can i retrieve the following Controller attributes in the view?
Controller name
Controller's #RequestMapping URI
Action method name
Action method's #RequestMapping URI
One approach which i have tried is by creating a subclass of HandlerInterceptorAdapter and overriding postHandle. I register my subclass as an mvc:interceptor for a list of given paths - which is clunky to maintain but was the only way to avoid my interceptor being called for ResourceHandler requests (which i don't want). In my postHandle i can easily add the 2 name attributes, but not the URIs...
Parsing from the HttpRequest object requires constraints on all Controller RequestMappings. I.e. i must always map /Controller/Action or equiv scheme. Quite limiting.
Creating an ApplicationContext and querying that with the requestURI is too long-winded.
I am thinking about dropping the HandlerInterceptorAdapter and instead defining a BaseController for all my controllers to extend.
I wanted to ask before i do this, is there a better approach?
You haven't stated why you need to do this (it sometimes helps to include your motivation, as others can suggest alternative approaches).
But I'm guessing that the Spring 3.1 features loosely termed "end point documentation" may do what you are asking... See RequestMappingHandlerMapping in the Spring documentation which doesn't provide a lot of detail, so this example project is the best place to see it in action:
Spring MVC 3.1 Demo App
example controller
example JSP page
I found that, by default when I using Spring MVC, "2010/01/02" binds correctly, but "2010-01-02" does not.
I know Spring has some useful binding mechanisms like initBinder. However, in this question I want to know where is the rule defined. Does anyone know that for example RFC documents of HTTP or Spring references.
It's just coincidence.
Spring MVC can implicitly convert input parameters to model objects via their single-argument constructor that takes String (if model objects have such constructors). Date has this constructor, though it's deprecated, so that this behaviour is determined by behaviour of that constructor.