ive been tasked with a total refactor of legacy code. It's a simple webservice, just an http request, then business logic with possibly a few database calls and a few other microservice calls, then a json response. I am being pushed not to use spring boot because no one else around me has used it before, and I was told jersey does everything spring boot does. I've never used jersey so im trying to find out how to do things that spring boot makes simple (ie repository layer with spring-data, caching, spring-consul, spring-zuul, spring-actuator, spring-circuit-breaker) It looks like jersey does do an analog of spring-security, bean validation, and easy insertion of servlet filters, but not everything spring-boot does. Is there an easy way to wire in a JPA type repository in jersey? I cant find it in the docs at https://jersey.java.net/documentation/latest/index.html.
I think about it this way. There are different layers in your application. You have a service layer, and you have a "REST layer". You access the Spring repositories with the service layer. Then you have the REST layer. With Spring, you have Spring MVC which is its web layer implementation, that you can also use as REST services. There is also Jersey, which is completely independent of Spring, which is a another REST layer options.
That be said, when using Spring MVC as the REST layer, adding the service layer with Spring data is seamless. But Jersey also has integration with Spring, that allows us to use Spring at the service layer inside our Jersey REST services. You check out this post which has some links to example of how this can be done (no hacking, this is supported out of the box). Using this approach, you can just injector your Spring data repositories into your Jersey resource class
interface PetsRepository extends JpaRepository<Pets, Long> {}
#Path("/pets")
class PetsResource {
#Autowired
private PetsRepository repo;
}
Now lets talk about Spring Boot. Spring Boot is just a bootstrapping framework. What it does is allow you to easily bootstrap an application without all the boilerplate configuration you would need without it. When your using Spring Boot for your REST services, you're not actually using Spring Boot itself as the REST service engine. You are only using it to bootstrap Spring MVC and maybe your Spring Data. But Spring MVC is the actual REST service engine.
Now like I said before, Jersey has support for integrating Spring into into it (for the service layer). Because of this support, Spring Boot has also provided a bootstrap configuration to integrate this support seamlessly. So instead of using the manual configuration that you would see in one of the examples linked to above, Spring Boot handles this configuration for us. So we can use Jersey as the REST layer, and Spring beans as the service layer. Check out the links below
See also:
Spring Boot docs for Jersey support
Related
My problem is when we use Spring boot like framework, we can easily handle AOP. but how we handle AOP with jersy jaxrs project
Spring Boot is just a bootstrapping framework. For REST we can use Spring Boot to bootstrap Spring MVC or Jersey fully integrated with Spring. If you choose the latter route, then you can use the Spring AOP with Jersey. All you need to do is make your Jersey resources Spring #Components to able to intercept them. See an official example of Spring Boot and Jersey.
If you don't want to use Spring Boot to bootstrap your Jersey app, then you can still integrate Spring with Jersey. Remember the AOP is not tied to Spring Boot, it is tied to the Spring Framework, which are different things. You can see an example of Jersey with Spring (without Spring Boot) here.
If you don't want to involve Spring at all, then Jersey has a DI framework, HK2, which has it's own AOP. You can see a full example here
I have a multi module Maven project. One of the modules is Spring backend that has DAOs, transactional services and REST controllers for some angular clients (Ionic framework)
Now I find the need to add a new Wicket module for a web client. This module uses the first module as a dependency. When I start the Wicket application the Spring context gets started from the dependency and the REST interface is available for the ionic clients. My issue is that I cannot tie the Wicket application to that existing Spring context. Wicket just wants to start a new Spring context with the same beans.
Now I can access the beans through some static methods from the spring context, but I want to use the #SpringBean annotation as in a regular Wicket+Spring application.
Is there a solution for this?
Thank you!
Wicket does not start any Spring context, as long as you don't instruct it to do so. Are you using the filter init-param "contextConfigLocation"?
When you just register a Spring injector inside your application, it should pick up the default Spring web context (it uses Spring's WebApplicationContextUtils#getRequiredWebApplicationContext()):
getComponentInstantiationListeners().add(new SpringComponentInjector(this));
If I understand correctly, your Spring backend is a web application, not just a java module. You cannot not (should not) have this web application as a dependency to an other web application (your new Wicket module).
You should probably move your shared business logic in a new java module. This new java module can be a dependency of your 2 web applications (Spring backend and Wicket).
An other solution would be to have 3 web applications. Spring facade, Wicket facade and Spring backend. Spring facade and Wicket facade, would just be some simple REST Controller which would redirect the request to the Spring backend to execute the business logic.
I am trying to learn Spring Framework, before that I used to create application with EJBs
[Web services]->[Business Layer]->[DAO Layer] | [Database]
in following way
WebServices: Restful API using Jersey with url mappings, that support both JSON and XML format( news/list.json, news/list.xml). Once a request is received by an endpoint(url-mapped-method) it is forwarded to a relevant EJB through lookup(remote, local). EJB process every thing, apply business rules and return result as DTO(Data transfer object),Service then transform the result into required format (JSON, XML)
Business Layer: Business Layer (Facade) implemented in EJB with remote and local interfaces, these EJBs can call other EJBs. WebService layer(and/or Timer service and MDBs) can also call any of the EJBs). For timer service related functionality I used EJB Timer Service and for Messages used Message Drive Bean and interceptor for logging and auditing.
DAO Layer: All the Database related functions(add,edit, delete, search) JPA/Hibernate using EntityManager are written here (Entity beans and HQL).
Seamless Transaction support, each EJB's method (lookup-based) call is treated as a separate transaction and calling methods of DAO layer are part of same transaction(provided that no extra configuration is provided). multiple operations are carried out in a single transaction If one db operation fails all others are roll backed automatically. Each Table is mapped as an entity class with relations etc.
I have worked on Spring MVC but could not map/understand correctly for above architecture
I know bit about AOP and that I think is a perfect replacement for Interceptors (or at least it work for me)
Now my question is how all these could be replaced in Spring framework?
Jersey (RestAPi) alternative in Spring>
EJB alternative in Spring (as EJB supports remoting, each lookup call to a method is treated as a transaction, calls to EJB's method could be intercepted and it comes with state-full and stateless flavors)?
Timer Service alternative in Spring?
Message Drive Bean alternative in Spring?
Interceptor alternative is AOP in Spring (As per my experience and that serve my purpose)
JPA(entity manager) alternative in spring?
Jersey (RestAPi) alternative in Spring?
Spring MVC does this perfectly fine, in my opinion. Just annotate your methods in your controller as the REST apis you want to use.
EJB alternative in Spring (as EJB supports remoting, each lookup call to a method is treated as a transaction, calls to EJB's method could be intercepted and it comes with state-full and stateless flavors)?
There is no full alternative. There are several techniques that implement this in parts: Spring remoting for remote calls, Spring transactions as transactions, Spring AOP interceptors for intercepting calls. However, for example XA transactions on remote calls are something you don't get as such in Spring. Spring however works fine with EJBs, so if you prefer them, you can still have them and use Spring in other parts of your software.
Timer Service alternative in Spring?
Spring task scheduling
Message Drive Bean alternative in Spring?
Message Listener Containers
Interceptor alternative is AOP in Spring (As per my experience and that serve my purpose)
There are several levels of interceptors in spring. There are handler interceptors in mvc, there are bean call interceptors like the SpringAutowiringInterceptor, and there are AOP-based interceptors that can be used in multiple layers.
JPA(entity manager) alternative in spring?
Spring has multiple of these as well. It's actually quite straightforward to just use JPA with Spring-Data, it's designed to integrate to JPA. There are Spring JDBC and other data layer alternatives though if Spring Data is not what you want.
Jersey (RestAPi) alternative in Spring ⇨ it's rest api (in spring with #Path annotation) or spring mvc if you want to use controllers (#Controller annotation)!
EJB alternative in Spring ⇨ Spring doesn't give statefull bean out of a box but you can use #Service annotation (or #Repository for DAO) but you have to handle transactions manually (with annotations for example)
Message Drive Bean alternative ⇨ There is no equivalent out of the box in Spring, you could use injection and librairies of Spring to get it working (package org.springframework.jms should contains what you need)!
JPA(entity manager) alternative is not ejb ⇨ so it can be used in Spring.
Spring is a lighweight library so you can do all you do with EJB but it's more configurable so you will have more work to do the same that EJB do. But this configuration brings you some advantages: you have the hand on it!
This explains Spring and Java EE (which is what you would have used EJBs in) side by side: http://www.slideshare.net/reza_rahman/java-ee-and-spring-sidebyside-34320697
Jersey offers Spring solutions too - see their website
Spring does support remote calls through, e.g., RMI; It also supports transactions; AFAIK, no explicit stateful/stateless Spring Components - it depends on how you use it
AFAIK nothing as awesome as TimerService, however, you could use Quartz
Spring offers MDPs (Message-Driven POJOs)
Spring does support JPA - see first link.
Another cool comparison slideshare: http://www.slideshare.net/kelapure/java-e-evsspringshootout
I want to create a REST web service using Jersey. I also want to use Spring in the project. Now, my questions is the following:
I don't see any reason for integrating these 2 together in my application. So, I should be able to use Spring for bean management and Jersey for creating the web service. Am I correct, or Spring and Jersey somehow have to be integrated.
I see that there is a jersey-spring maven project, and so, I assume that this is for the purpose of integrating jersey and spring together. My question here is do I get any benefit of using this integrated form rather than simply use Jersey and Spring separately each for its own functionality?
Thanks,
Cyrus
You can absolutely combine the two projects. However, I would encourage you to look at Spring-MVC for doing REST as it is very powerful and easy to use. If memory serves, the jersey-spring project was helpful in integration of JAXB and other touch points. Again, this is all built into Spring. And if you use Spring-Boot it is amazingly simple to get running.
The jersey-spring project provides integration between Jersey and Spring. It allows you to wire in any beans in your Spring context into Jersey and vice-versa.
For instance, if you are using spring-security, it will provide your spring-security principal when wiring the Jersey specific SecurityContext into any of your REST resources.
If you want to access Spring beans from your Jersey REST endpoints (or use Spring Beans as implementations for your JAX-RS interfaces) you need to integrate Spring and Jersey, otherwise it won't work. If you don't have any connections between Spring beans and your REST endpoints, then it is not necessary.
I think your first statement is correct. I have used Jersey and Sprint as separate entities.
Jersey is really awesome to create a web server.
Spring is useful for dependency injection (beans) and other cools stuff.
About your second statement, I do not know anything jersey-spring maven project.
My suggestion/opinion is to do as your first comment. Use them in a separate way. You will have the best of both worlds. Using jersey-spring maven project might be a complication and maybe it is not what you want. Libraries usually are intend to be independent.
Question is, what's the difference between Spring HATEOAS versus Spring Data Rest ?
I feel both can do the same, and Spring Data Rest (as part of Spring Data) seems a bit more alive.
https://github.com/spring-projects/spring-hateoas
https://github.com/spring-projects/spring-data-rest
When would you use one or the other?
Spring HATEOAS provides common abstractions (representational models, a Link class, API to build links pointing to Spring MVC controllers, etc.) to ease building hypermedia driven REST APIs with Spring MVC in general. Thus, you can use it alongside Spring MVC to manually build those services.
Spring Data REST uses Spring HATEOAS to automatically expose resources for entities managed by Spring Data repositories and leverages hypermedia aspects to do pagination, link entities etc. So it covers the 80% use case for the basic stuff and allows you to selectively add more complex processes using manually implemented controllers later on.
To get a feel for this, feel free to have a look at the Spring RESTBucks sample project. The handling of Order instances is completely done by Spring Data REST (with some minor tweaks to implement business constraints). The entire payment logic is then implemented manually as the process does not fall into the CRUD category as we actually need to implement certain steps and a protocol to complete the order. Again, the code is here, a slide deck with some additional visuals can be found at speakerdeck.com.
HATEOAS stand for Hypermedia as the Engine of Application State and is one of the key ponit of REST. Basically the key point consist to use links on the your resource representation for map the valid transition of the application state. In this case will be the service provider that provide the valid next correct state of the your application reachable through the link. Spring HATEOAS is the Spring projects for help to build the Hymeridia Controls in your Resource. It is a project integrate with Spring MVC and you can think as the Spring MVC extension for building a real RESTFull WS whit a very good support for increase the level of the your service form CRUD (level 2 of maturity in the Richardson model) to an Hypermedia aware (level 3 of maturity in the Richardson model). Spring Data Rest on the other hands is a very nice project that use Spring HATEOAS as basic brick, for give you a repository layer usable as restfull ws. In proctis the project help to reduce the classical boliporlent code for expose the your repository layer as a restfull endpoint. We can say tat was the propouse of the projects very different. With Spring HATEOAS you had a framework usable for any kind of restfull endpoint, with spring data rest you had a spring project that already provide an endpoint and a framework for customize it.
I hope that this reflections can help you to clarify the difference between the two projects and understand better how use one or the other
I chose to use both of them in my project. One layer of controllers was built with Spring Data REST. The other layer of controllers was #RestController's (spring-wevmvc). In this layer I used Spring HATEOAS to create customed page's.
(Process was :
1.creating Pageable Pageable pageable = new PageRequest
2. creating new Page Page<FooDt> page = new PageImpl<FooDt>
3.creating PagedResources PagedResources<Resource<FooDt>> resource = fooAssembler.toResource(page, fooAssembler) after that process using Jackson's ObjectMapper to return json.
The solution that I found for loading to context both technologies - is using two DispatcherServlet's.
Otherwise, Spring Data Rest is taking control and there is no option to use other controllers. ( In that way I had two domains in my app. One for Data Rest and one for webmvc+HATEOS).