In Spring, bean scope is used to decide which type of bean instance should be return from Spring container back to the caller.There are 5 types of bean scopes that spring supports:
singleton – Return a single bean instance per Spring IoC container
prototype – Return a new bean instance each time when requested
request – Return a single bean instance per HTTP request. *
session – Return a single bean instance per HTTP session. *
globalSession – Return a single bean instance per global HTTP session. *
In most cases, you may only deal with the Spring’s core scope – singleton and prototype, and the default scope is singleton
An Example showing the difference between singleton and prototype is presented as under:
Singleton Scope example
If no bean scope is specified in bean configuration file, it defaults to singleton. Below is the configuration file "Spring-Customer.xml"
Now when we run the program we get the following output:
The test program is as under:
Now run the program:
The output is as under:
Since the bean ‘customerService’ is in singleton scope, the second retrieval by ‘custB’ will display the message set by ‘custA’ also, even it’s retrieve by a new getBean() method. In singleton, only a single instance per Spring IoC container, no matter how many time you retrieve it with getBean(), it will always return the same instance.
update the "Spring-Customer.xml" file to define its scope as prototype as under:
When you run the test program again. the output is as under:
In prototype scope, you will have a new instance for each getBean() method called.
you can also use annotations to define bean scope
Now enable auto component scanning in the "spring-customer.xml"file as under: