I would like add an annotation similar to #RequestParam, though have it pull the values from the request attribute rather than the request param...
Is there an example or explanation how to create my own annotation for this and the handler / binder needed as well?
Thanks
The blog entry with the title "Extending Spring MVC's annotation controller" answers your question. Google it to find it since Stackoverflow won't let me create the direct link.
Basically you create an #RequestAttribute annotation and then a custom WebArgumentResolver.
The blog entry has examples for #RequestAttribute and #SessionAttribute.
The svn directory with the examples is here.
http://impala-extensions.googlecode.com/svn/trunk/impala-extension-mvc/src/org/impalaframework/extension/mvc/
Since Spring 4.3 #RequestAttribute annotation is a part of Spring MVC, so there is no need to create your own #RequestAttribute annotation
Related
As of spring 4.1, spring controllers accept return value that can be of type ListenableFuture. is returning a ListenableFuture return value sufficient in making the controller async? Or does it also need #enableAsync annotation somewhere in spring configuration file or/and anything else? I am following this tutorial
I found out that what i was looking for is not #enableAsync but a servlet 3.0 property called async-supported. According to this link, spring-boot defaults async-supported to true.
Hence, there is no need of any further configuration to do if you're using spring-boot.
I have been looking at various examples of how to use Spring with REST. Our end target is a Spring HATEOAS/HAL setup
I have seen two distinct methods for rendering REST within Spring
Via #RestController within a Controller
Via #RepositoryRestResource within a Repository
The thing I am struggling to find is why would you use one over the other. When trying to implement HAL which is best?
Our database backend is Neo4j.
Ok, so the short story is that you want to use the #RepositoryRestResource since this creates a HATEOAS service with Spring JPA.
As you can see here adding this annotation and linking it to your Pojo you have a fully functional HATEOAS service without having to implement the repository method or the REST service methods
If you add the #RestController then you have to implement each method that you want to expose on your own and also it does not export this to a HATEOAS format.
There is a third (and fourth) option that you have not outlined, which is to use either #BasePathAwareController or #RepositoryRestController, depending on whether you are performing entity-specific actions or not.
#RepositoryRestResource is used to set options on the public Repository interface - it will automatically create endpoints as appropriate based on the type of Repository that is being extended (i.e. CrudRepository/PagingAndSortingRepository/etc).
#BasePathAwareController and #RepositoryRestController are used when you want to manually create endpoints, but want to use the Spring Data REST configurations that you have set up.
If you use #RestController, you will create a parallel set of endpoints with different configuration options - i.e. a different message converter, different error handlers, etc - but they will happily coexist (and probably cause confusion).
Specific documentation can be found here.
Well, above answers are correct in their context still I am giving you practical example.
In many scenarios as a part of API we need to provide endpoints for searching an entity based on certain criteria. Now using JPA you don't have to even write queries, just make an interface and methods with specific nomenclature of Spring-JPA. To expose such APIs you will make Service layer which would simply call these repository methods and finally Controllers which will expose endpoints by calling Service layer.
What Spring did here, allow you to expose these endpoints from such interfaces (repositories) which are generally GET calls to search entity and in background generates necessary files to create final endpoints. So if you are using #RepositoryRestResource then there is no need to make Service/Controller layer.
On the other hand #RestController is a controller that specifically deals with json data and rest work as a controller. In short #Controller + #ResponseBody = #RestController.
Hope this helps.
See my working example and blog for the same:
http://sv-technical.blogspot.com/2015/11/spring-boot-and-repositoryrestresource.html
https://github.com/svermaji/Spring-boot-with-hibernate-no-controller
#RepositoryRestController override default generated Spring Data REST controllers from exposed repository.
To take advantage of Spring Data REST’s settings, message converters, exception handling, and more, use the #RepositoryRestController annotation instead of a standard Spring MVC #Controller or #RestController
E.g this controllers use spring.data.rest.basePath Spring Boot setting as base path for routing.
See Overriding Spring Data REST Response Handlers.
Be aware of adding #ResponseBody as it is missed in #RepositoryRestController
If you not exposed repository (marked as #RepositoryRestResource(exported = false)), use #BasePathAwareController annotation instead
Also be aware of bags
ControllerLinkBuilder does not take Spring Data REST's base path into account and #RequestMapping shouldn't be used on class/type level
and
Base path doesn't show up in HAL
Workaround to fix link: https://stackoverflow.com/a/51736503/548473
UPDATE: at last I prefer not to use #RepositoryRestController due to lot of workarounds.
I'd like to use #Valid annotation to validate my beans in controller method. Unfortunatelly it does not work. I know that in order to make it work I'd have to include spring-mvc into my project and put there mvc:annotation-driven or #EnableMvc... .
But I do not use spring-mvc! I use Wicket framework. How to make #Valid working without incorporating spring-mvc?
Thanks!
#Valid is not specific to spring it is an implementation of JSR 303 bean validation. You can use any other reference implementation or write your own. e.g Apache and Hibernate Validator has reference implementation available. Take a look at this answer Is there an implementation of JSR-303 (bean validation) available?
Can anyone explain what I need to do to implement my own annotation that would add functionality to my web requests?
For example:
#Controller
public class MyController {
#RequestMapping("/abc")
#RequiresSomeSpecialHandling
public void handleSecureRequest() {
}
}
Here #RequiresSomeSpecialHandling would be my own annotation that causes some special work to be done before or after the given web request /abc.
I know that on a very high level I would need to write a bean post processor, scan classes for my annotations, and inject custom mvc interceptors when needed. But are there any shortcuts to simplify this task? Especially for the two examples above.
Thanks in advance,
This kind of Annotations, (that add additional functionality when invoking a method) looks like annotations that trigger an AOP Advice.
#see Spring Reference Chapter 7. Aspect Oriented Programming with Spring
The idea is to use the Annotation to trigger the AOP Advice.
like:
#Pointcut("#target(com.example.RequiresAuth)")
Depends on what you want to do as a result of #RequiresSomeSpecialHandling. E.g. do you want it to influence request mappings or the invocation of the method (i.e. resolving method arguments, processing the return value)?
The support for annotated classes in Spring 3.1 became much more customizable. You can browse some examples in this repo.
Also keep in mind that a HandlerInterceptor in Spring 3.1 can cast the handler Object to HandlerMethod, which gives you access to the exact method including its annotations. That may be enough for what you need to do.
If caching is one of your goals, take a look at the #Cacheable annotation (and its siblings #CachePut, #CacheEvict and #Caching), available as of Spring 3.1.
I'm using Spring 3 and using SimpleFormController is deprecated. It sounds like we should use annotions like #Controller instead.
Okay, but how can I manage the validator for my form within my controller?
Thanks
Still some issues with 3.0RC1, see the following issue if you want to look at annotation based validation and JSR 303: http://jira.springframework.org/browse/SPR-6189
Spring 3 has shiny new support for JSR 303 validation. See the docs here.