What is the @bean annotation?

@Bean is a method-level annotation and a direct analog of the XML <bean/> element. The annotation supports most of the attributes offered by <bean/> , such as: init-method , destroy-method , autowiring , lazy-init , dependency-check , depends-on and scope .

What is the use @bean annotation?

One of the most important annotations in spring is the @Bean annotation which is applied on a method to specify that it returns a bean to be managed by Spring context. Spring Bean annotation is usually declared in Configuration classes methods. This annotation is also a part of the spring core framework.

What is bean annotation in Spring boot?

Spring @Bean annotation tells that a method produces a bean to be managed by the Spring container. It is a method-level annotation. During Java configuration ( @Configuration ), the method is executed and its return value is registered as a bean within a BeanFactory .

What does @bean do in Spring?

The @Bean annotation returns an object that spring registers as a bean in application context. The logic inside the method is responsible for creating the instance.

What is the use of @bean in Spring boot?

@Bean is used to explicitly declare a single bean, rather than letting Spring do it automatically. It decouples the declaration of the bean from the class definition and lets you create and configure beans exactly how you choose. @Bean is a method-level annotation.

Spring boot @Bean annotation with example

What is difference between @bean and @component?

@Component is a class level annotation whereas @Bean is a method level annotation and name of the method serves as the bean name. @Component need not to be used with the @Configuration annotation where as @Bean annotation has to be used within the class which is annotated with @Configuration.

What is @inject in Spring boot?

Dependency Injection is a fundamental aspect of the Spring framework, through which the Spring container “injects” objects into other objects or “dependencies”. Simply put, this allows for loose coupling of components and moves the responsibility of managing components onto the container.

What is bean scope?

Bean Scopes refers to the lifecycle of Bean that means when the object of Bean will be instantiated, how long does that object live, and how many objects will be created for that bean throughout. Basically, it controls the instance creation of the bean and it is managed by the spring container. Bean Scopes in Spring.

What is bean file in Java?

JavaBeans are classes that encapsulate many objects into a single object (the bean). It is a java class that should follow following conventions: Must implement Serializable. It should have a public no-arg constructor. All properties in java bean must be private with public getters and setter methods.

What is IoC and DI in Spring?

Spring IoC (Inversion of Control) Container is the core of Spring Framework. It creates the objects, configures and assembles their dependencies, manages their entire life cycle. The Container uses Dependency Injection(DI) to manage the components that make up the application.

What is @configuration and @bean?

Annotating a class with the @Configuration indicates that the class can be used by the Spring IoC container as a source of bean definitions. The @Bean annotation tells Spring that a method annotated with @Bean will return an object that should be registered as a bean in the Spring application context.

Can we use @bean at class level?

No. It is used to explicitly declare a single bean, rather than letting Spring do it automatically. If any class is annotated with @Component it will be automatically detect by using classpath scan. We should use @bean, if you want specific implementation based on dynamic condition.

Can we use @bean without @configuration?

@Bean methods may also be declared within classes that are not annotated with @Configuration. For example, bean methods may be declared in a @Component class or even in a plain old class. In such cases, a @Bean method will get processed in a so-called 'lite' mode.

What is @component annotation in Spring?

@Component is an annotation that allows Spring to automatically detect our custom beans. In other words, without having to write any explicit code, Spring will: Scan our application for classes annotated with @Component. Instantiate them and inject any specified dependencies into them. Inject them wherever needed.

What is @controller and @RestController?

@Controller is used to mark classes as Spring MVC Controller. @RestController annotation is a special controller used in RESTful Web services, and it's the combination of @Controller and @ResponseBody annotation. It is a specialized version of @Component annotation.

Where @autowired can be used?

The @Autowired annotation provides more fine-grained control over where and how autowiring should be accomplished. The @Autowired annotation can be used to autowire bean on the setter method just like @Required annotation, constructor, a property or methods with arbitrary names and/or multiple arguments.

Why beans are used in Java?

Why use JavaBean? According to Java white paper, it is a reusable software component. A bean encapsulates many objects into one object so that we can access this object from multiple places. Moreover, it provides easy maintenance.

What is JavaBean properties?

JavaBeans Properties

A JavaBean property is a named attribute that can be accessed by the user of the object. The attribute can be of any Java data type, including the classes that you define. S.No. For example, if property name is firstName, your method name would be getFirstName() to read that property.

How do you declare a JavaBean?

What is bean life cycle?

The lifecycle of any object means when & how it is born, how it behaves throughout its life, and when & how it dies. Similarly, the bean life cycle refers to when & how the bean is instantiated, what action it performs until it lives, and when & how it is destroyed.

What is bean Autowiring?

When autowiring a property in a bean, the property name is used for searching a matching bean definition in the configuration file. If such a bean is found, it is injected into the property. If no such bean is found, an error is raised. Read More : Autowire byName example.

What is singleton in Spring?

Singleton scope in Spring means that same object at same memory location will be returned to same bean id. If one creates multiple beans of different ids of the same class then container will return different objects to different ids.

What is @inject and Autowired?

@Inject and @Autowired both annotations are used for autowiring in your application. @Inject annotation is part of Java CDI which was introduced in Java 6, whereas @Autowire annotation is part of spring framework. Both annotations fulfill same purpose therefore, anything of these we can use in our application.

What is difference between @bean and Autowired?

@Bean is just for the metadata definition to create the bean(equivalent to tag). @Autowired is to inject the dependancy into a bean(equivalent to ref XML tag/attribute).

What is the difference between @autowired and @qualifier?

The difference are that @Autowired and @Qualifier are the spring annotation while @Resource is the standard java annotation (from JSR-250) . Besides , @Resource only supports for fields and setter injection while @Autowired supports fields , setter ,constructors and multi-argument methods injection.