The core of spring framework is it’s bean factory and mechanisms to create and manage such beans inside Spring container. The beans in spring container can be created in five scopes i.e. singleton, prototype, request, session and global-session. They are called spring bean scopes.
1. Spring bean scopes
More Updated Version : Bean Scopes in Spring 5
All the scope names are self-explanatory but lets make them clear so that there will not be any doubt.
1.1. singleton
This bean scope is default and it enforces the container to have only one instance per spring container irrespective of how much time you request for its instance. This singleton behavior is maintained by bean factory itself.
1.2. prototype
This bean scope just reverses the behavior of singleton scope and produces a new instance each and every time a bean is requested.
Remaining three bean scopes are web applications related. Essentially these are available through web aware application context (e.g. WebApplicationContext). Global-session is a little different in sense that it is used when application is portlet based. In portlets, there will be many applications inside a big application and a bean with scope of ‘global-session’ will have only one instance for a global user session.
1.3. request
With this bean scope, a new bean instance will be created for each web request made by client. As soon as request completes, bean will be out of scope and garbage collected.
1.4. session
Just like request scope, this ensures one instance of bean per user session. As soon as user ends its session, bean is out of scope.
1.5. global-session
It is something which is connected to Portlet applications. When your application works in Portlet container it is built of some amount of portlets. Each portlet has its own session, but if your want to store variables global for all portlets in your application than you should store them in global-session. This scope doesn’t have any special effect different from session scope in Servlet based applications.
2. How to define spring bean scope
2.1. XML bean configuration file
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
<bean id="demoBean" class="com.howtodoinjava.application.web.DemoBean" scope="session" />
</beans>
2.2. Java configuration – @Scope annotation
@Service
@Scope("session")
public class DemoBean
{
//Some code
}
Drop me your questions in comments section.
Happy Learning !!
Sangram
Hi Lokesh,
Could you please explain details about when we use bean scope as “prototype”?
Lokesh Gupta
Use prototype when you want to create a new instance everytime. This is mostly done for the stateful beans (beans which have class fields that are shared with multiple instances of the class).
java
There are other scopes are also available like
application
websocket
Thread Scope
abhimanyu kumar
HI Lokesh,
Can you please explain how single bean(Singleton bean) used by different users. Ie how Spring manage session internally.
Anurag Kadam
Hi Lokesh,
I encountered with this question in one of the interviews. What will happen if we give the dependency of a prototype scoped bean inside a singleton bean? It will be very helpful if you can give any real life example. Thanks in advance..
Lokesh
As singleton beans are created only once, so the instance of prototype scope bean will be created only once when singleton bean is created. This is NOT the desired behavior because prototype bean instance MUST be created everytime singleton bean instance is fetched from spring context.
To overcome this problem, we use lookup method injection. Read more on this SO Thread.
Prabhath Balakrishnan
Hi Lokesh,
Can’t we use scoped proxy beans for this?
Thanks,
Prabhath
Ankit
Can you suggest a use case for this ?
Having different instances of a bean inside a Singleton bean can create problems i think. Correct me if i am wrong. Is this a good practise ?
Ukash Satış
thank you for this post. I m really wondering about the spring bean scrope. Thank you really.
Adarsh S
Hi Lokesh,
I am newly started Spring. I am using STS tool for spring project. When i started working with some core programming i am getting
“Caused by: java.io.FileNotFoundException: class path resource [src/main/java/net/core/example/app-context.xml] cannot be opened because it does not exist”
Error. I placed app_context.xml in class path , tried with several changes but still getting same error. Please help me .
If i used same code without using repository(adding only spring jars) it works better But with maven repository i am getting error.
Code :
ApplicationContext ac = new ClassPathXmlApplicationContext
(“/src/main/java/net/core/example/app-context.xml”);
Error log :
Exception in thread “main” org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from class path resource [src/main/java/net/core/example/app-context.xml]; nested exception is java.io.FileNotFoundException: class path resource [src/main/java/net/core/example/app-context.xml] cannot be opened because it does not exist
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:341)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:302)
Lokesh
verify what you have configured in web.xml. It will look something like this.
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/employee-servlet.xml</param-value>
</context-param>
Adarsh S
Hi Lokesh,
I am not using any web application example.i stated from core Spring written simple application. when i added maven dependency to application i got error.
srikanth
hi lokesh,
scope examples plzz..one by one
Lokesh Gupta
I have written separate posts containing examples. Please find here. https://howtodoinjava.com
joshiaseem
Hi Lokesh,
Can you tell me some real life programming examples (in brief) where to use singleton and where to use prototype. for eg : in a flipkart application where we gonna use singleton and where prototype.
Thanks in Advance!
Sekhar
Worth reading.. Thanks for your time and efforts.