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Spring prototype beans with parameters?

Is it possible to define a prototype bean, using XML config or annotation-based config such that I can get an instance of the bean with a custom parameter value? My use case is a message queue handler that makes API calls with different parameter values that are supplied in the inbound message.
In this case it seems I can do one of two things:
Get an instance of my prototype-scope bean and then call setters to customize it to be specific to the inbound message.
Construct a new instance of the bean class using a plain new MyPrototypeBean() and then call setters to customize the instance.
Perhaps a different way of wording my question is: What is the benefit of using a prototype-scope bean vs. using a simple Java constructor?

To get a prototype bean from another bean while passing arguments to constructor you can use <lookup-method> (XML Configuration) or #Lookup (annotation-based configuration).
If you want to get the prototype instance from "unmanaged" code (not from a bean) or you don't want to use the lookup methods, you can achieve the same using org.springframework.beans.factory.BeanFactory.getBean(String beanName, Object...).
Answering your second question, difference between a prototype-scope bean and using a simple Java constructor is that the prototype-scope bean still have access to Spring container's features. This includes, but it's not limited to the following: it can have collaborators provided in XML configuration (<property name="someCollaborator" ref="..."/>) or with annotations (#Resource, #Autowired, ...), t can implement Spring-aware interfaces (like ApplicationContextAware so that the prototype bean itself has access to the container).

Set Spring MVC Paths in Java Config

Can Spring MVC paths be set as Java config, rather than using annotations on the controller?
I want to re-use one controller class under different path mappings, and have each instance wired with different service implementations.
For example, the API will look a bit like this:
PUT /mysql/some_key/some_value
GET /mysql/some_key
DELETE /mysql/some_key
PUT /oracle/some_key/some_value
GET /oracle/some_key
DELETE /oracle/some_key
So there'd be one instance of the controller wired with a MySqlCrudService and one instance of the controller with an OracleCrudService.
How would one configure this? The controller could have the methods annotated (eg #RequestMapping(method=RequestMethod.PUT, value="/{key}/{value}"), but when constructing the controller in Java config I'd need to specify the class-level path mapping.

Spring 4 conditional - Accessing a resource

Doing my first steps with spring 4 I tried the #Conditional annotation following this article.
My problem -
I would like to get access to a classpath resource (basically a properties file) from method matches in class OnSystemPropertyCondition.
To do that currently I'm loading the required properties file from the matches method every time it is invoked (which means for every class annotated with the ConditionalOnSystemProperty annotation).
This is a bit ugly. I thought that an elegant solution would be to simply autowire my resource or some properties (using the #Value annotation) but this can't be done since this class gets instanciated before the beans.
Any suggestions than can help me avoid reload this resource again and again?

The single method of the annotation gets in its signature the input param ConditionContext context. You can obtain an Environment from the context by calling context.getEnvironment(). The environment gives access to all my resources (look at this to see how to get access to your resources via spring environment).

Spring beans and changing bean parameter in application life cycle

I have a web application that is based on Spring. There is defined a bean that holds some class MyClass that is passed also with beans to MyEndpoint that extends AbstractMarshallingPayloadEndpoint.
MyClass has set some boolean parameter in beans to true.
If my application will change this parameter programically to false, does next request will have it also set to false or it will contains a default bean parameter - true ?

It depends on the scope of the bean (which will default to singleton, if you don't specify one).
If it is of singleton scope, there is one instance of that bean in the application context, and each time you ask for that bean, you get that single instance. If you change it in a request with this scope, then the change will be maintained.
If it is of prototype scope, a new instance is given to you (created with the same parameters) each time you ask the application context for it. If you change it in a request with this scope, then the change will be ignored when you get another instance of this object.
These are the two most commonly used (at least with my time in Spring). There are other scopes (request, session, globalsession), but you should read the documentation on them that Spring provides.

If you want this property to change dynamically according to your application business logic and not only to be reset on every new request (otherwise Request scope will do the magic) consider Factory Methods (especially Lookup Method Injection)

Spring session bean: initialize with values

I've a doubt about Spring session bean. Let me try to explain what I need and what I did. I need to store on a session variable (in that case a Bean) the user_id so, when I need to create some record on db I can keep track of who did what.
To do that, for first, I created a bean and, second, I modified my application context in that way:
<bean id="UserInfo" class="net.agdev.session.UserInfo" scope="session">
<aop:scoped-proxy/>
</bean>
I read that using this :
ContextLoader.getCurrentWebApplicationContext().getBean("UserInfo");
is ppossible to access to the bean, but it's not yet clear how to fill that bean..
I tryed to read on Spring documentation how to initalize the bean and how to recall on my Class controller but I didn't find anything.
Could you suggest where to find an example or a tutorial to do that?
many thanks!
Andrea

You mean how to get the user_id into the session bean? Depending on your application this should probably happen right after the user "logged in". Meaning, if you for instance have a login webflow or controller, set the user_id in your session bean within that webflow or controller.
So if I understood your context correctly this has only very little to do with Spring itself and mostly with your application :-)
If you want other aspects of your bean initialized for instance from operations on other services you could set an init-method on the bean definition as detailed here.

By aspect programming like AspectJ. You have to set some trigger, for example after an user does something you have to read your bean and fill it the operation info that have been performed by the user.
You can use #annotation to define trigger or you can do it by spring xml file. I think you have to use an application context bean and not a session bean.