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Spring Boot Cheat Sheet

Spring Boot 备忘单

注释

Annotation	Description	Example
@SpringBootApplication	Marks a class as a Spring Boot application. Enables auto-configuration and component scanning.	@SpringBootApplication
@RestController	Indicates that a class provides RESTful endpoints. It combines @Controller and @ResponseBody annotations.	@RestController
@RequestMapping	Maps HTTP requests to handler methods of RESTful controllers.	@RequestMapping("/api")
@Autowired	Injects dependencies into a Spring bean. It can be used for constructor, setter, or field injection.	@Autowired private MyService myService;
@Component	Indicates that a class is a Spring-managed component. It is automatically detected during component scanning.	@Component
@Repository	Marks a class as a Spring Data repository. It handles data access and persistence logic.	@Repository
@Service	Marks a class as a service component in the business layer. It is used to separate business logic from presentation logic.	@Service
@Configuration	Indicates that a class provides bean definitions. It is used along with @bean to define beans in Java-based configuration.	@Configuration
@Value	Injects values from properties files or environment variables into Spring beans.	@Value("${my.property}") private String property;

控制流程

初始化：Spring Boot 首先加载应用程序属性和自动配置 bean。
组件扫描：Spring 扫描控制器、服务和存储库等组件。
Bean 创建：Spring 创建 Bean 并使用依赖注入解析依赖关系。
请求处理：传入的 HTTP 请求根据请求映射映射到控制器方法。
执行：控制器方法处理请求、与服务交互并返回响应。
响应渲染：Spring 将方法返回值转换为适当的 HTTP 响应（例如 JSON）。

Spring Boot 备忘单中的错误处理

错误处理是构建健壮应用程序的一个关键方面。 Spring Boot 提供了多种优雅处理错误和异常的机制，确保流畅的用户体验。

错误类型

客户端错误：无效客户端请求导致的错误，例如 400 Bad Request 或 404 Not Found。
服务器错误：服务器端发生的错误，例如500内部服务器错误。
验证错误：由于输入无效或数据验证失败而导致的错误。

错误处理机制

1. 控制者建议

@ControllerAdvice：用于在 Spring MVC 中定义全局异常处理程序的注解。
@ExceptionHandler：用于处理控制器建议中的特定异常的注释。
示例：

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(MyException.class)
    public ResponseEntity<ErrorResponse> handleMyException(MyException ex) {
        ErrorResponse response = new ErrorResponse("My error message");
        return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleException(Exception ex) {
        ErrorResponse response = new ErrorResponse("Internal server error");
        return new ResponseEntity<>(response, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

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响应实体异常处理程序

ResponseEntityExceptionHandler：处理常见 Spring MVC 异常的基类。
重写：重写handleMethodArgumentNotValid、handleHttpMessageNotReadable等方法
示例：

@ControllerAdvice
public class CustomExceptionHandler extends ResponseEntityExceptionHandler {

@Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(
        MethodArgumentNotValidException ex, HttpHeaders headers, HttpStatus status, WebRequest request) {
    ErrorResponse response = new ErrorResponse("Validation failed");
    return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);
}

// Other overrides for handling specific exceptions

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3. 错误属性

ErrorAttributes：用于自定义错误响应内容和格式的接口。
DefaultErrorAttributes：Spring Boot 提供的默认实现。

@Component
public class CustomErrorAttributes extends DefaultErrorAttributes {
@Override
public Map<String, Object> getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {
    Map<String, Object> errorAttributes = super.getErrorAttributes(webRequest, includeStackTrace);
    errorAttributes.put("customAttribute", "Custom value");
    return errorAttributes;
}

}

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