I am currently studying Spring.
While reading a Spring book, I met a part regarding Event.
By using context.publishEvent(..), I could trigger the event.
But I don't know what It's exactly for.
I can use other Method instead of using complicated publishEvent.
Please, tell me. thank you.
Spring Events are used to implement publish-subscribe model (or observer pattern) where two not-related parts of code must be somehow connected.
Think of the analogy of web applications where servlet container creates http sessions and your code is informed about this using javax.servlet.http.HttpSessionListener.
Spring uses this mechanism internally. It's much more visible in Spring Security where several parts of the code are informed about e.g., successfull authentication.
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There is an amazing mechanism is spring: Spring Application Events, I see it helps to build loosely coupled application, implement observer pattern, reactor pattern.
My question is, what is the trigger in Spring application architecture when Spring Application Events is absolutely inevitable? Actually any application classes relationship can be build using events only as well as using class associations and hierarchy only (i'm talking about monolith service now).
May be it's more architectural question, but what is the threshold when it's need to consider events between objects inside a spring application?
Could it be definitely seen the cases when Spring Application Events absolutely needed?
Spring Security pushes events on certain event occurrences. See list of events
In some cases, it's much better to push message instead invoke a method in a classical way. Eg if you need to invoke the same function I multiple places in the code, just to notify another object.
It allows us to build a system which utilizes event-driven architecture. Read more
Helps in solving a producer-consumer problem
Send emails by pushing event object to ApplicationEventPublisher See Spring Higher-Order Components and #EnableEmailSending
I have a use case where I would like build a common interface or service which can update entities of application. Example case is shown as below:
Now every application has to handle update functionality of entities. Rather than implementing update functionality in n application module. I would like to build a common interface or server in spring boot.
Service will be like below:
My question is how to design service/interface which can used for above scenario. Any api or tool which can help me to achieve this. I dont want to write code for update in every application module.
Thanks in advance.
Last year I was thinking about the similar concept to yours, but in Apache Camel framework context. I haven't got enough time and motivation to do so, but your post encouraged me to give it a try - perhaps mostly because I've found your concept very similar to mine.
This is how I see it:
So basically I considered an environment with application that might uses N modules/plugins that enriches application's features, i.e. processing feature etc. Application uses module/plugin when it is available in the classpath - considering Java background. When the module is not available application works without its functionality like it was never there. Moreover I wanted to implement it purely using framework capabilities - in this case Spring - without ugly hacks/ifs in the source code.
Three solutions come to my mind:
- using request/response interceptors and modifying(#ControllerAdvice)
- using Spring AOP to intercept method invocations in *Service proxy classes
- using Apache Camel framework to create a routes for processing entities
Here's the brief overview of POC that I implemented:
I've chosen Spring AOP because I've never been using it before on my own.
simple EmployeeService that simulates saving employee - EmployeeEntity
3 processors that simulates Processing Modules that could be located outside the application. These three modules change properties of EmployeeEntity in some way.
one Aspect that intercepts "save" method in EmployeeService and handles invocation of available processors
In the next steps I'd like to externalize these Processors so these are some kind of pluggable jar files.
I'm wondering if this is something that you wanted to achieve?
link to Spring AOP introduction here: https://docs.spring.io/spring/docs/5.0.5.RELEASE/spring-framework-reference/core.html#aop
link to repository of mentioned POC: https://github.com/bkpawlowski/spring-aop
We have a spring boot application that is growing in complexity because of integration needs - like send an email after you do this, or broadcast a jms message after you that etc. In looking for some higher level abstractions, I came across apache camel (haven't used camel ever before). The question that I have is what do I do with the spring boot application? The application has the standard spring controllers, services and uses spring-data for connecting to databases. I didn't find much help online on how to merge camel into a spring-boot restful application. Is that even something that is doable or is camel a completely different beast that the spring boot won't fit?
I did read that Camel tightly integrates with Spring, but still I didn't know if 1) Spring Controllers are still something that can be used along with Camel 2) If I can call the other spring beans from camel routes and whether I can call invoke a camel route from a spring bean (sorry if these sound like camel newbie questions to the experts)
As an example of what we have to do:
After finishing writing anything to the database about an order, we have to send an email out to the order processing department
If someone deletes a particular user address, we have to send to a jms topic so other applications can take action.
Every http request is coming in through the Spring MVC stack today.
Is there a way to "hand-off" the processing to camel after a particular task is complete? (like writing the order to the database successfully via the Spring MVC stack and hand off to camel to send a jms message and do other things)? Or should we completely replace Spring with Camel?
Not sure what the right path is. Can someone please guide us?
This question is slightly old, but though it was worth mentioning here that Apache Camel now includes a Spring Boot component.
Details can be found here
http://camel.apache.org/spring-boot.html
and they document an example here
http://camel.apache.org/spring-boot-example.html
Follow this for the current best practice in camelising a spring boot application!
One option is to
1> define camel routes either in Spring DSL or Java DSL or other means and define it in Spring Application context.
2> And have a class that implements ApplicationContextAware and cache the Spring ApplicationContext in a Static Variable.
3> For #Controller we can get this static variable and get hold of ApplicationContext .
4> With the camel context ID we can do a getBean from ApplicationContext.
5> This is the instance of DefaultCamelContext,with this we can do a createProducer and call camel routes from #Controller.
Like some others mentioned, spring-boot-camel (but use spring-boot-camel-starter as your dependency) works very well and it is really easy to set up. When you annotate your RouteBuilder extensions and your Processor implementations with #Component, they wire up directly into the context and you are good to go. Then, you can #Autowire a CamelContext or a ProducerTemplate into your classes and use them as necessary.
You asked about how Controllers can work with Camel, and if you #Autowire any of the things you need (probably a context or a producer template), then the answer is a definite "yes" that you can use them together quite easily. And when you use spring-web, your context will start and remain running without any additional configuration, etc.
Like Matthew Wells suggested, the links will get you pointed in the right direction. If you, or others on your team, are at all familiar with Camel, then it will be very easy for you to do what you need to do. But, ah, I notice that this question is from 2014, and you're probably well past the point of your question. At least if anyone else stops by this thread, they will have plenty of information to get going. If you come by and re-visit your question, please let us know how it went for you, and what you ended up doing. Cheers!
I wanted to know whether it is possible to have custom handler execution just before spring authentication manager. I wanted to validate licenses for the user before he access system. Initially i wrote custom filter and executed it before calling to authentication manager, but in this case he wont be able to access some resources since he is not authenticated, but later i moved my code to sucessHandler of spring which worked fine, except it has some security issues like if open in multiple tabs it fails.
Any help is highly appreciated.
Thanks,
Brijesh
I think what you are looking for is to add a Spring AuthenticationProvider. In short, an AuthenticationManager has a list of AuthenticationProviders, each of which is queried in order. The question and answer to Multiple Authentication Providers in Spring Security has a good explanation of this. The Spring documentation also explains how the various components fit together.
I am using struts2.0 for my project named online examination system.
I am using traditional JDBC approach in datya access layer. I can't use JPA.
I want to make entire service layer transactional, but i searched for the transaction support in struts2 but didn't get anything.
Although spring provides good support for making service layer transactional.
Please help me on this issue to find out transaction support in struts2.
You are on a wrong track here.Struts2 is only for MVC part and what you are doing at your service layer it has nothing to do with that.
If you want to take advantage of transaction API i suggest you to use either Spring AOP of if i am correct Google Guice also provides a way for AOP.
Whatever you use at your service layer for transaction handling Struts2 is independent of it and out of context