Question: What Is @Qualifier Annotation In Spring?

What is @qualifier in Java?

A qualifier type is a Java annotation defined as @Target({METHOD, FIELD, PARAMETER, TYPE}) and @Retention(RUNTIME).

For example, you could declare an @Informal qualifier type and apply it to another class that extends the Greeting class..

What is @profile annotation in spring?

Spring 3.1 introduced the annotation @Profile. … It can be used on type-level annotation on any class or it can be used as a meta-annotation for composing custom stereotype annotations or as a method-level annotation on any @Bean method. Essence is, @Profile is used to conditionally activate/register.

What is lazy initialization in spring?

By default in Spring, all the defined beans, and their dependencies, are created when the application context is created. In contrast, when we configure a bean with lazy initialization, the bean will only be created, and its dependencies injected, once they’re needed.

What is the purpose of @qualifier annotation?

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.

What is an example of a qualifier?

Qualifiers and intensifiers are words or phrases that are added to another word to modify its meaning, either by limiting it (He was somewhat busy) or by enhancing it (The dog was very cute).

What is required annotation in spring?

The @Required annotation in spring is a method-level annotation applied to the setter method of a bean property and thus making the setter-injection mandatory. This annotation indicates that the required bean property must be injected with a value at the configuration time.

How does annotation work in spring?

Spring could use its own classloader to load required classes. At runtime, when the class is loaded and Spring determines it has some appropriate annotation, it injects bytecode to add additional properties or behavior to the class.

Why annotation is used in spring?

Starting from Spring 2.5 it became possible to configure the dependency injection using annotations. So instead of using XML to describe a bean wiring, you can move the bean configuration into the component class itself by using annotations on the relevant class, method, or field declaration.

What is the use of Autowired annotation in spring?

The @Autowired annotation in spring automatically injects the dependent beans into the associated references of a POJO class. This annotation will inject the dependent beans by matching the data-type (i.e. Works internally as Autowiring byType).

How do I activate Spring profile?

Spring profiles can also be activated via Maven profiles, by specifying the spring. profiles. active configuration property. This command will package the application for prod profile.

How do I know if my spring profile is active?

First you will want to autowire the environment bean. Then you can use getActiveProfiles() to find out if the profile exists in the list of active profiles.

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.