This is the sixth day of my participation in the August More text Challenge. For details, see: August More Text Challenge

Recently gathered useful annotations used by developers and packaged them into this Spring annotations cheat sheet. From the basic annotations needed to start the project, to the service discovery annotations, we have provided you with help.

Important Spring annotations

Here are the most important annotations that any Java developer using Spring should know:

  • @Configuration – Used to mark the class as the source of the bean definition. Beans are system components that you want to wire together. The method tagged with @bean annotation is the Bean producer. Spring will handle the lifecycle of the bean for you, and it will use these methods to create the bean.
  • @ComponentScan – Used to make sure Spring knows about your configuration classes and can initialize beans correctly. It causes Spring to scan for packages configured for the @Configuration class.
  • @import – If you need more precise control over configuration classes, you can always use @import to load additional configurations. This method works even if you specify beans in an XML file, as you did in 1999.
  • @Component – Another way to declare a bean is to tag a class with the @Component annotation. Doing so converts the class to Spring beans during automatic scanning.
  • ** @service -** Marks the specialization of @Component. It tells Spring that it is safe to manage them more freely than regular components. Remember that services have no encapsulated state.
  • @Autowired – To wire together parts of your application, use @Autowired on fields, constructors, or methods in your component. Spring’s dependency injection mechanism connects the appropriate beans to class members tagged with @AutoWired.
  • Bean – a method level annotation that specifies the return Bean managed by the Spring context. The returned bean has the same name as the factory method.
  • @lookup – Tells Spring to return an instance of the method’s return type when we call it.
  • @primary – When there are more than one bean of the same type, one bean is preferred.
  • @required – indicates that the setter method must be configured to use values for dependency injection at configuration time. Use @required on setter methods to flag dependencies populated with XML. Otherwise, throw BeanInitializationException.
  • @value – Used to assign values to fields in A Spring-managed bean. It is compatible with constructors, setters, and field injection.
  • Lazy – Causes bean to delay initialization. The @Lazy annotation can be used for any class annotated directly or indirectly with @Component or method annotated with @Bean.
  • @Scope – To define the Scope defined by the @Component class or @Bean. It can be a singleton, prototype, request, session, global session, or custom Scope.
  • Profile – Add beans to the application only if the Profile is active.

With these annotations, you can easily group applications together. Sure, you might want to use more Spring annotations, but these are the core of the framework, which implements the flexibility Spring is known for!

Important Spring Boot annotations

Let’s take a look at some of the most commonly used annotations in Web applications. It makes sense to popularize Spring Framework annotations that make Web development easier.

@SpringBootApplication

One of the most basic and useful annotations is @SpringBootApplication. It’s the syntactic sugar for combining other annotations, which we’ll cover later. @SpringBootApplication is a combination of the @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations, with their default properties configured.

@ the Configuration and @ ComponentScan

The @Configuration and @ComponentScan annotations we described above enable Spring to create and configure the beans and components of an application. This is a good way to link the actual business logic code to the application.

@EnableAutoConfiguration

Now the @enableAutoConfiguration annotation is better. It lets Spring guess the configuration based on the JAR files available on the classpath. It can find out which libraries you are using and pre-configure their components without you having to lift a finger. This is how all spring-boot-starter libraries work. This means that it is a major lifesaver both when you first start using the library and when you know and believe that the default configuration is reasonable.

Important Spring MVC Web annotations

The following annotations enable Spring to configure your application as a Web application capable of providing an HTTP response.

  • @controller – Mark this class as a Web Controller capable of handling HTTP requests. Spring looks at the methods of the class tagged with the @Controller annotation and creates a routing table to know which methods serve which endpoints.
  • @responsebody – @responsebody is a utility annotation that causes Spring to bind the return value of a method to the HTTP ResponseBody. When building JSON endpoints, this is a magical way to magically transform your objects into JSON for easy use.
  • @RestController – And then the @RestController annotation, which is a handy syntax for @Controller and @responseBody. This means that all the action methods in the tag class will return a JSON response.
  • @RequestMapping(method = RequestMethod.GET, value = “/path”) – @RequestMapping(method = RequestMethod.GET, The value = “/path”) annotation specifies a method in the controller that should be responsible for servicing HTTP requests to a given path. Spring will handle the implementation details of how this is done. You simply specify the path value on the annotation, and Spring will route the request to the correct action method.
  • @requestParam (value=”name”, defaultValue=”World”) – Of course, the method that handles the request may require parameters. To help you bind HTTP parameters to action method parameters, you can use the @requestParam (value=”name”, defaultValue=”World”) annotation. Spring will parse the request parameters and put the appropriate parameters into your method parameters.
  • @pathVariable (” empty name “) – Another common way to provide information back end is to encode it in the URL. You can then use the @pathVariable (” empty name “) annotation to bring the values from the URL to the method parameters.

One last thing I want to say

In this article, we learned about a number of annotations that Java developers should be aware of when using the Spring framework. We’ve covered the most common and probably most important annotations — from annotations that enable dependency injection for components to ways to bind code to respond to HTTP requests.

I have been writing a tech blog for a long time and this is one of my tech articles/tutorials. Hope you like it! Here is a summary of all my original and work source code: GitHub, and this is I recently just set up the blog: Haiyong. Site, there is no content, put some HTML games, interested in can try, source code can own F12 copy, or directly find me to.

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