Spring scopes behaviour with respective to single and multiple web request/session - spring

Question

Whenever I try to analysis to understand the spring scopes I am stuck up somewhere. Below is my understanding from my analysis and before conclude myself I would like to confirm with you. Please correct me if my understanding is wrong.
<bean id="signupController" class="com.crp.controller.SignupController"
scope="">
If scope is "request", then for every new request from client irrespective of session, the spring container will generate new instance. Once the request is completes then spring container will manage to close the life cycle of instance.
If scope is "session", then for first request of a session a new instance will be generated by spring container and maintain it for all the client request for that particular session. Once the session timed out then spring container will manage to close the life cycle of instance.
If scope is "prototype", new instance will be generated by spring container whenever the bean is requested irrespective of session. Developer should manage the life cycle of the instance because spring container will not manage life cycle of prototype scope.
If scope is "singleton", only one instance generated by spring container and maintain it to be available for all request irrespective of sessions. For every session a copy of singleton instance will be maintained so that the one session singleton object will not share by another session and spring container will manage the life cycle of the copy of singleton instance and close it when session timed out.
Note: I believe most of you may have different opinion in my understanding on singleton scope. Even I am also confused in the behaviour of singleton scope and getting different information during my analysis. Please share your thoughts
Thank you.
For singleton scope how container works for below implementation for multiple user (session) send request at same time.
Login.java:
public class Login {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
LoginController.java:
public class LoginController extends MultiActionController {
private Login login;
public ModelAndView submitLogin(HttpServletRequest request,
HttpServletResponse response) {
String userName = request.getParameter("username");
String password= request.getParameter("password");
getLogin().setUserName(userName);
getLogin().setPassword(password);
// TODO send login bean to DAO for executing further business logic.
}
public Login getLogin() {
return login;
}
public void setLogin(Login login) {
this.login = login;
}
}
context.xml:
<bean id="login" class="com.crp.bean.Login" scope="singleton">
</bean>
<bean id="loginController" class="com.crp.controller.LoginController" scope="singleton">
<property name="login" ref="login"></property>
</bean>

Answer 1

No, that's not entirely correct.
If scope is "request", then for every new request from client irrespective of session, the spring container will generate new instance.
No. The bean instance will only be created if the code calls a method on the bean (i.e. on the scoped proxy that wraps the actual bean instance). But you're right that every request has a bean instance that is different from the other requests, and that the bean is destroyed at the end of the request (i.e. its life-cycle hooks, if they exist, are called when the request ends).
If scope is "session", then for first request of a session a new instance will be generated by spring container and maintain it for all the client request for that particular session.
Same remark as for the request scope: the bean instance is created on-demand.
If scope is "prototype", new instance will be generated by spring container whenever the bean is requested irrespective of session.
Right. But note that you need to request a bean instance to the spring context to get a new instance. If you inject a prototype to a singleton bean, the singleton bean will keep a reference to this bean for all of its life, and the same prototype bean will thus be used every time the singleton bean calls it.
If scope is "singleton", only one instance generated by spring container and maintain it to be available for all request irrespective of sessions. For every session a copy of singleton instance will be maintained so that the one session singleton object will not share by another session and spring container will manage the life cycle of the copy of singleton instance and close it when session timed out.
No. That is completely wrong. No copy is made at all. A single instance is created, injected everywhere, and used concurrently everywhere. The bean is only destroyed when the application itself ends.