Spring Framework de Java

Anotaciones

@Controller	Annotation to indicate that the class is a controller class.
@RestController	A convenience annotation that is itself annotated with `@Controller` and `@ResponseBody`. Used in controllers that will behave as RESTful resources.
@RequestMapping	Annotation to be used on methods in `@RestController` classes. You can provide an URI to be served as RESTful service.
@ModelAttribute	Annotation used to bind values present in views.

@Configuration	Annotation used to provide configurations.
@Bean	Annotation that acts like a provider where you can define how the bean is instantiated when a injection of that type is requested. Instances of `@Bean` annotated methods will act as singletons.

Command-line arguments	`java -Dproject.name=Test -jar app.jar`
System properties	`System.getProperties()`
Environment Variable	`export PROJECT_NAME=Test`
External properties/yml file	`project.name=Test`
Internal properties/yml file	`project.name=Test`

The default properties/yml files are application.properties and application.yml and they are located in /src/resources.

http://start.spring.io	Web service that allows the user to specify the project metadata and dependencies as well as download the initial structure.
Spring CLI	A CLI tool that interacts with http://start.spring.io service to scaffold a new project.
Spring Tool Suit	Eclipse-based IDE that also interacts with http://start.spring.io to scaffold a new project.
Intellij IDEA	Intellij also provides a way of creating a new project via http://start.spring.io.

@ConditionalOnClass	`@ConditionalOnClass(Tomcat.class)`	Only available if the Tomcat class is found in the classpath.
@ConditionalOnProperty	`@ConditionalOnProperty(name = "tomcat.version", matchIfMissing = true)`	Only available if the property `tomcat.version` is set to true.

Auto configuration is just the combination of @Configuration and @Conditional* annotations in order to correctly register beans.

@Resource	Annotation used to inject an object that is already in the Application Context. It searches the instance by name. It also works on setter methods.
@Autowired	Annotation used to inject objects in many possible ways, such as: instance variable, constructor and methods. It does not rely on name as `@Resource`, so, for multiple concrete implementations, the `@Qualifier` annotation must be used with it.
@Qualifier	Annotation used to distinguish between multiple concrete implementations. Used alongside with `@Autowired` annotation that does not rely on name.
@Primary	Annotation used when no name is provided telling Spring to inject an object of the annotated class first. Used along with `@Component`.
@Component	Generic stereotype annotation used to tell Spring to create an instance of the object in the Application Context. It’s possible to define any name for the instance, the default is the class name as camel case.
@Controller	Stereotype annotation for presentation layer.
@Repository	Stereotype annotation for persistence layer.
@Service	Stereotype annotation for service layer.

spring.profiles.active	Property to be set in application.properties in order to tell Spring what profiles are active.
@Profile(«!dev»)	Annotation used to define which profile can execute the annotated method.

@SpringBootApplication	Initial annotation that comprises the following annotations: `@SpringBootConfiguration`, `@EnableAutoConfiguration` and `@ComponentScan`.
@SpringBootConfiguration	Indicates that a class provides Spring Boot application `@Configuration`.
@EnableAutoConfiguration	Enable auto-configuration of the Spring Application Context, attempting to guess and configure beans that you are likely to need.
@ComponentScan	Configures component scanning directives for use with `@Configuration` classes.

Most of the time you will need only to declare the @SpringBootApplication annotation.