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应用中的异常，有两件事要考虑，怎么处理这个异常，怎么把异常可读性高地返回给前端用户
1.怎么把异常可读性高的返回给前端用户或API的消费者
自定义错误代码和错误内容
2.怎么处理异常
比如遇到某个异常时需要发邮件通知IT团队
@ControllerAdvice 是 Spring Framework 提供的一个注解，用于定义全局的异常处理、数据绑定和模型属性的增强。
它的主要作用是集中管理控制器的全局逻辑，例如异常处理，而不需要在每个控制器中重复编写相同的代码。
主要功能
全局异常处理：通过 @ExceptionHandler 注解 捕获并处理控制器中抛出的异常。
全局数据绑定：通过 @InitBinder 注解对请求参数进行预处理。
全局模型属性：通过 @ModelAttribute 注解为所有控制器提供公共的模型数据
3.自定义错误代码和内容，并且使用@ControllerAdvice统一处理异常
3.1 自定义错误码，可以把Demo换成projectname
public enum ExceptionCode {IN_VALID_REQUEST("Demo0001", ""),BAD_REQUEST("Demo400", "Bad Request"),NOT_FOUND("Demo404", "Resource Not Found"),INTERNAL_SERVER_ERROR("Demo500", "Internal Server Error");private final String code;private final String message;ExceptionCode(String code, String message) {this.code = code;this.message = message;}public String getCode() {return code;}public String getMessage() {return message;}
}3.2 自定义异常InvalidationException
public class InvalidationRequestException extends RuntimeException {public InvalidationRequestException(String message) {super(message);}public InvalidationRequestException(String message, Throwable cause) {super(message, cause);}
}3.3 自定义ExceptionAdvice，统一处理exception
当controller中抛出InvalidationRequestException时，就会被@ControllerAdvice 中的 @ExceptionHandler handleInvalidationException()方法捕获并处理该异常
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;import java.util.HashMap;
import java.util.Map;@ControllerAdvice
public class GlobalExceptionHandler {private static final Logger logger = LoggerFactory.getLogger(GlobalExceptionHandler.class);@ExceptionHandler(InvalidationRequestException.class)@ResponseBodypublic ResponseEntity<Map<String, String>> handleInvalidationException(InvalidationRequestException ex) {logger.warn("InvalidationRequestException: {}", ex.getMessage());//其它异常处理逻辑，比如发邮件，打电话通知IT团队//返回给UI或API消费者Map<String, String> response = new HashMap<>();response.put("code", ExceptionCode.IN_VALIDATED_REQUEST.getCode());response.put("detail",ex.getMessage());return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(response);}@ExceptionHandler(Exception.class)public ResponseEntity<String> handleGenericException(Exception ex) {return new ResponseEntity<>("An error occurred: " + ex.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);}
}3.4 controller， 抛出InvalidationException异常
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;@RestController
public class DemoController {@GetMapping("/validate")public String validateParameter(@RequestParam String input) {if (input == null || input.trim().isEmpty()) {throw new InvalidationRequestException("Input parameter is invalid or empty");}return "Input is valid: " + input;}
}3.5 测试
启动应用，访问 http://localhost:8082/validate?input
校验失败时，返回http状态码是400，body如下
{"code": "Demo0001","detail": "Input parameter is invalid or empty"}==========================================
1.异常直接抛出
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
public class DemoController {@GetMapping("/throwException")public String throwException() {throw new RuntimeException("This is a runtime exception!");}
}启动应用，访问 http://localhost:8082/throwException
会获得一个状态码为500的异常 An error occurred: This is a runtime exception!
思考：这个异常对用户或者call API的消费者来说，可读性太低，不能明确的知道是什么错误
2.自定义状态码和错误信息，返回给前端用户或者API 消费者可读性高的异常
自定义错误码，可以把Demo换成projectname
public enum ExceptionCode {IN_VALIDATED_REQUEST("Demo0001", ""),BAD_REQUEST("Demo400", "Bad Request"),NOT_FOUND("Demo404", "Resource Not Found"),INTERNAL_SERVER_ERROR("Demo500", "Internal Server Error");private final String code;private final String message;ExceptionCode(String code, String message) {this.code = code;this.message = message;}public String getCode() {return code;}public String getMessage() {return message;}
}controller抛出异常
import com.example.demo_async.exception.ExceptionCode;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.HashMap;
import java.util.Map;@RestController
public class DemoController {@GetMapping("/testErrorCode")public ResponseEntity<Map<String, String>> testErrorCode() {Map<String, String> response = new HashMap<>();response.put("code", ExceptionCode.BAD_REQUEST.getCode());response.put("detail", ExceptionCode.BAD_REQUEST.getMessage());return new ResponseEntity<>(response, HttpStatus.BAD_REQUEST);}
}返回http status 400， body 如下
{"code": "Demo400","detail": "Bad Request"}思考：如果有很多个controller方法都会抛出这个异常，就需要在每个方法里写一遍异常处理的逻辑，会产生大量的重复代码，怎么解决呢？