What is the difference between Singleton pattern and singleton bean in Spring?

Spring Singleton is very different from Singleton pattern. Spring guarantees to create only one bean instance for given bean id definition per container. Singleton pattern ensures that one and only one instance is created per ClassLoader.

Does Spring use Singleton pattern?

Spring does not force you to use the Singleton pattern.

What is the difference between singleton class and singleton bean?

Singleton: Only one instance will be created for a single bean definition per Spring IoC container and the same object will be shared for each request made for that bean. Prototype: A new instance will be created for a single bean definition every time a request is made for that bean.

Can we create multiple singleton beans of same class in Spring?

It will throw an error at runtime, as you can not define two Sspring beans of the same class with Singleton Scope in XML. (Very rare) The reference check will return true, as the container maintains one object. Both bean definitions will return the same object, so the memory location would be the same.

Can we inject singleton bean in prototype bean in Spring?

You cannot dependency-inject a prototype-scoped bean into your singleton bean, because that injection occurs only once, when the Spring container is instantiating the singleton bean and resolving and injecting its dependencies.

Is Spring @component a singleton?

Yes, that is correct, @Component is a Spring bean and a Singleton. About singletons – spring beans are all in singleton scope by default.

Why singleton Bean is not thread-safe?

If there is any global variable defined the singleton class then it will not be thread safe because if multiple thread share the singleton object and execute the method which can updates the global variable it will not be thread safe.

Can we call prototype bean in singleton bean?

Is singleton from Spring container thread-safe?

Because the singleton isn’t thread-safe, calls to its prototype methods may also run concurrently. When several threads share the singleton, the single instance of the prototype that Spring injects to that singleton will also be shared.

What is the difference between @bean and configuration?

@Configuration – It is like beans. xml but Java-based bean configuration. It means class annotated with this annotation is the place where beans are configured and will be a candidate for auto-detection. In this class, methods are annotated with @Bean which return an object of the class.

Why default scope of Spring bean is singleton?

When a bean is a singleton, only one shared instance of the bean will be managed and all requests for beans with an id or ids matching that bean definition will result in that one specific bean instance being returned. Only when you have to keep some session details you should use for example session scope.

Why singleton beans are not thread-safe in Spring framework?

Singleton spring beans has no relation with thread safety. spring container only manages life-cycle of objects and guaranteed that only one object in spring container. so If an Non thread safe object is injected then obviously it is not thread safe. To make it thread safe you have to handle it by coding.