The CommandLineRunner interface indicates that a bean should run when it is contained within a SpringApplication . It can be used to create command line applications in Spring Boot. The CommandLineRunner is also a Spring bean and is decorated with the @Component annotation; it is auto-detected by Spring.Herein, what is use of @qualifier in spring?
The @Qualifier annotation is used to resolve the autowiring conflict, when there are multiple beans of same type. The @Qualifier annotation can be used on any class annotated with @Component or on method annotated with @Bean . This annotation can also be applied on constructor arguments or method parameters.
Furthermore, what is @qualifier in Java? You can use qualifiers to provide various implementations of a particular bean type. A qualifier is an annotation that you apply to a bean. A qualifier type is a Java annotation defined as @Target({METHOD, FIELD, PARAMETER, TYPE}) and @Retention(RUNTIME).
Moreover, what is the use of @autowired in spring boot?
Autowiring feature of spring framework enables you to inject the object dependency implicitly. It internally uses setter or constructor injection. Autowiring can't be used to inject primitive and string values. It works with reference only.
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.
What does @autowired do?
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.What is the difference between @bean and @component?
Both approaches aim to register target type in Spring container. The difference is that @Bean is applicable to methods, whereas @Component is applicable to types. @Component is a class level annotation where as @Bean is a method level annotation and name of the method serves as the bean name.What is the use of qualifier?
The @Qualifier annotation is used to resolve the autowiring conflict, when there are multiple beans of same type. The @Qualifier annotation can be used on any class annotated with @Component or on methods annotated with @Bean . This annotation can also be applied on constructor arguments or method parameters.What is difference between @autowired and @resource in spring?
The primary difference is, @Autowired is a spring annotation. Whereas @Resource is specified by the JSR-250, as you pointed out yourself. So the latter is part of Java whereas the former is Spring specific. Hence, you are right in suggesting that, in a sense.What is use of @repository in spring?
Spring @Repository annotation is used to indicate that the class provides the mechanism for storage, retrieval, search, update and delete operation on objects.What is @configuration in spring?
@Configuration annotation is used for Spring annotation based configuration. The @Configuration is a marker annotation which indicates that a class declares one or more @Bean methods and may be processed by the Spring container to generate bean definitions and service requests for those beans at runtime.What is the use of BeanFactory in spring?
What is BeanFactory in Spring? Answer: A BeanFactory is like a factory class that contains a collection of beans. The BeanFactory holds Bean Definitions of multiple beans within itself and then instantiates the bean whenever asked for by clients.What is @RequestMapping?
@RequestMapping is one of the most widely used Spring MVC annotation. org. RequestMapping annotation is used to map web requests onto specific handler classes and/or handler methods. @RequestMapping can be applied to the controller class as well as methods.What is difference between @inject and @autowired?
You can annotate fields and constructor using @Autowired to tell Spring framework to find dependencies for you. The @Inject annotation also serves the same purpose, but the main difference between them is that @Inject is a standard annotation for dependency injection and @Autowired is spring specific.How @autowired will work?
Autowiring happens by placing an instance of one bean into the desired field in an instance of another bean. Both classes should be beans, i.e. they should be defined to live in the application context. This means that the context instantiates the objects, not you.Which is better setter or constructor injection?
Overriding: Setter injection overrides the constructor injection. If we use both constructor and setter injection, IOC container will use the setter injection. It doesn't create a new bean instance always like constructor. So setter injection is flexible than constructor injection.What is the difference between PathVariable and RequestParam?
1) The @RequestParam is used to extract query parameters while @PathVariable is used to extract data right from the URI. Even though both are used to extract data from URL, @RequestParam is used to retrieve query parameters, anything after ? in the URL, while @PathVariable is used to retrieve values from URI itself.What is spring life cycle?
Spring (Coffee) Bean Lifecycle. The Spring IoC (Inversion of Control) container manages Spring beans. A “Spring bean” is just a Spring-managed instantiation of a Java class. The Spring IoC container is responsible for instantiating, initializing, and wiring beans. The container also manages the life cycle of beans.Why do we need dependency injection?
Dependency injection is a programming technique that makes a class independent of its dependencies. That enables you to replace dependencies without changing the class that uses them. It also reduces the risk that you have to change a class just because one of its dependencies changed.Can we Autowire an interface?
Why do we autowire the interface and not the implemented class? Firstly, it is always a good practice to code to interfaces in general. Secondly, in case of spring, you can inject any implementation at runtime. A typical use case is to inject mock implementation during testing stage.What are spring annotations?
Spring Annotations. Spring framework implements and promotes the principle of control inversion (IOC) or dependency injection (DI) and is in fact an IOC container. Traditionally, Spring allows a developer to manage bean dependencies by using XML-based configuration. That's why Spring annotations were introduced.What is the difference between controller and rest controller?
1. The @Controller is a common annotation which is used to mark a class as Spring MVC Controller while @RestController is a special controller used in RESTFul web services and the equivalent of @Controller + @ResponseBody. 
