CODEWITHSUNDEEP
springspring-mvcjavabeans
Jatin
Jatin

Reputation: 31724

Constructors in Bean

I have one small issue with creating a new bean. Basically as per request, I get some parameters, which needs to be passed to a bean. Below I am instantiating ControllerService for each request. Rather I would like it to be a bean with scope=protype. So that I get a fresh object for every request. But then how do i set the 2 properties (kpiName, kpiInput) that I am sending via constructors in the bean??

@Autowired
@Qualifier("serviceManager")
Cleanser serviceManager;  

@RequestMapping(method = RequestMethod.POST)
public @ResponseBody
String getKPIResult(@RequestParam("kpiName") String kpiName,
            @RequestParam("kpiInput") String kpiInput) {    

    return serviceManager.checkAndExecute(new ControllerService(kpiName, kpiInput));
}

Upvotes: 1

Views: 592

Answers (2)

pap
pap

Reputation: 27614

Don't. The Controller as it's intended in Spring MVC is largely derived from the old Java servlet, which should be stateless by specification.

In fact, Controller-objects are hard-cached inside the handler mapping framework and not fetched from the bean context on each request. Setting scope to "prototype" would, effectively, do nothing as the handler (controller) is really only gotten once.

Upvotes: 1

DeejUK
DeejUK

Reputation: 13481

In situations like this where you're going against the grain of Spring, I'd suggest that perhaps you're doing something in a way that's not considered best practice. Without more context it's hard to see though.

Spring Social uses a request scope bean to embody a repository for a specific user. I've now idea why as it's a horribly inefficient way of doing things, and much less understandable IMHO.

<bean id="connectionRepository" factory-method="createConnectionRepository"
    factory-bean="usersConnectionRepository" scope="request">
    <constructor-arg
        value="#{T(org.springframework.security.core.context.SecurityContextHolder).getContext().getAuthentication().getPrincipal()}" />
    <aop:scoped-proxy proxy-target-class="false" />
</bean>

You can see here the use of factory-bean and factory-method to declare a class/method to call when wanting an instance of your class. The constructor argument is passed using SpEL. I'm not quite sure how you'd achieve this with Spring MVC responding to web requests, but I'm fairly sure you could use Spring Integration to pass a message and use SpEL to grab headers/payload form that message to pass to the constructor.

Again though, I'd really question your design pattern here - a more usual SOA idiom is to create services on startup, and have them as stateless as possible from there-on in, rather than create an instance with specific state for each request. Best of luck!

Upvotes: 1

Related Questions