Annotations are used to define a class, property, or method that a program can compile. It also acts as an explanatory file. Tells the program what a class or attribute is annotated by a particular annotation and what to do about it. Annotations can be used to annotate packages, classes, methods, and variables.
1. Commonly used annotations on classes
| annotations | Use location | instructions |
|---|---|---|
| @RestController | In the name of the class | @RestController=@Controller + @RequestBody When the front and back ends are separated, it is used to return DATA in JSON or XML format |
| @Controller | In the name of the class | Declare the current class to be a controller layer, equivalent to C (controller) in the MVC development pattern |
| @Service | In the name of the class | Declare the current class to be a business processing class that annotates the service layer and handles the business logic class |
| @Reporitory | In the name of the class | Used to annotate the data access layer |
| @Component | In the name of the class | Generic annotations that can mark any class asSpringComponents. This can be used if a Bean does not know which layer it belongs to@ComponentAnnotation annotation. |
| @Configuration | In the name of the class | It is used to declare configuration classes@ComponentAnnotations are used instead, howeverConfigurationAnnotation declaration configuration classes are more semantic |
| @Resource | On a class name, property, or constructor parameter | Both @autoWired and @autoWired can be used to assemble beans, with byType auto-injection by default |
| @Autowired | On a class name, property, or constructor parameter | Automatically import objects into classes. Injected classes are also managed by the Spring container. ByName is automatically injected by default |
| @RequestMapping | Class name or method | Used to handle request address mapping |
| @Transactional | Class name or method | Used on the method to start a transaction@TransactionalAnnotations can be |
| @Qualifier | Class name or property | Often used with @AutoWired to indicate which implementation class needs to be injected |
| @JsonIgnoreProperties | In the name of the class | Used to filter out specific fields without returning or parsing |
| @Transient | On the properties | Declare the field that does not need to be mapped to the database, do not need to save into the database when saving, virtual field |
2. Common annotations to methods
| annotations | Use location | instructions |
|---|---|---|
| @Bean | On the way | Declare a Bean and hand it over to Spring to manage. |
| @ReponseBody | On the way | After converting the object returned by the method to JSON or XML format, write the body data area of the Response object |
| @RequestBody | Method parameter before | In short, you convert a JSON string into a Java object |
| @PathVariable | Method parameter before | Map the parameters obtained from the URL to the method |
| … |
3. Other commonly used notes
| annotations | Use location | instructions |
|---|---|---|
| @EnableAutoConfiguration | Entry class, class name | Enabling Automatic Configuration |
| @SpringBootApplication | Entry class, class name | Start the entry class Application(@SpringBootApplication is considered a collection of @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations.) |
| @EnableScheduling | Entry class, class name | Used to start scheduled tasks, such as scheduled tasks |
| @EnableAsync | Entry class, class name | Enable asynchronous annotations |
| @ComponentScan | Entry class, class name | Used to scan components to see beans automatically discovered and assembled |
| @Aspec | Entry class, class name | Annotated facets that can be used to configure transactions, logging, permission validation, and so on |
| @ControllerAdvice | In the name of the class | Contains @Component, which can be scanned and handled uniformly |
| @ExceptionHandler | On the way | Indicates that the method is executed when the exception is encountered |
| @Value | On the properties | Used to get the value in the configuration file |
| … |
4. To summarize
Of course, SpringBoot provides us with a lot of annotations for developers, the above article is just a summary of the common SpringBoot development process of some annotations, and a brief description of the role or purpose of their annotations.