为了项目的正常运行中,异常捕获,记录也是非常重要的，方便我们排查问题，定位问题 # 定义异常为了方便定位异常，自定义了几种异常类，方便我们快速定位异常。 ## 基类 ```java public class HttpException extends RuntimeException { protected String code; protected Integer httpStatusCode = 500; } ``` ## ParameterException ```java public class ParameterException extends HttpException { public ParameterException(String code){ this.code = code; this.httpStatusCode = 400; } } ``` ## ServerErrorException ```java public class ServerErrorException extends HttpException { public ServerErrorException(String code) { this.code = code; this.httpStatusCode = 500; } } ``` ## UnAuthenticatedException ```java public class UnAuthenticatedException extends HttpException{ public UnAuthenticatedException(String code){ this.code = code; this.httpStatusCode = 401; } } ``` ## ForbiddenException ```java public class ForbiddenException extends HttpException { public ForbiddenException(String code) { this.code = code; this.httpStatusCode = 403; } } ``` ## NotFoundException ```java public class NotFoundException extends HttpException { public NotFoundException(String code){ this.httpStatusCode = 404; this.code = code; } } ``` 这里定义了我在项目中常用的几种异常，也可根据实际情况定义自己所需的异常。 # 捕获异常捕获异常需要用到一个注解`@ControllerAdvice`,关于它的详细解释可查看[文档](https://docs.spring.io/spring-framework/docs/5.0.0.M1/javadoc-api/org/springframework/web/bind/annotation/ControllerAdvice.html)。使用方法如下，定义一个异常捕获类 ```java @ControllerAdvice public class GlobalExceptionAdvice { } ``` 这个类就已经实现了捕获全局异常的功能，下面在加上上面定义的几种异常 ```java @ControllerAdvice public class GlobalExceptionAdvice { @ExceptionHandler(UnAuthenticatedException.class) public ResponseEntity unAuthenticatedException(UnAuthenticatedException e) { return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(e.getCode()); } @ExceptionHandler(ParameterException.class) public ResponseEntity handleParameterException(ParameterException e) { return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getCode()); } @ExceptionHandler(ForbiddenException.class) public ResponseEntity handleForbiddenException(ForbiddenException e) { return ResponseEntity.status(HttpStatus.FORBIDDEN).body(e.getCode()); } @ExceptionHandler(NotFoundException.class) public ResponseEntity handleNotFoundException(NotFoundException e) { return ResponseEntity.status(HttpStatus.NOT_FOUND).body(e.getCode()); } @ExceptionHandler(RuntimeException.class) public ResponseEntity handleRunTimeException(RuntimeException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(500); } } ``` `@ExceptionHandler`注解表示该方法捕获的异常类型，就可以在不同的异常中进行不同的处理方式。 # 记录异常捕获到异常之后我们要记录下来，方便我们对bug的追踪解决。记录方法有多种多样的，比如记录到数据库或者`log`文件中。我使用了第二种方式。 ## 加入依赖 ```xml org.projectlombok lombok true commons-logging commons-logging 1.2 org.apache.logging.log4j log4j-api 2.2 org.apache.logging.log4j log4j-core 2.2 org.apache.logging.log4j log4j-jcl 2.2 ``` ## 增加日志配置文件 `logback.xml` ```xml %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n UTF-8 ./logs/info/log-stack.log true INFO ACCEPT DENY ./logs/info/log-stack.%d{yyyy-MM-dd}.log 30 %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n UTF-8 ./logs/error/log-stack.log true ERROR ACCEPT DENY ./logs/error/log-stack.%d{yyyy-MM-dd}.log 30 %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n UTF-8 ./logs/debug/log-stack.log true DEBUG ACCEPT DENY ./logs/debug/log-stack.%d{yyyy-MM-dd}.log 30 %d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} %L - %msg%n UTF-8

``` ## 写入日志 ```java @ControllerAdvice @Slf4j public class GlobalExceptionAdvice { @ExceptionHandler(ParameterException.class) public ResponseEntity handleParameterException(ParameterException e) { log.error(e.getLocalizedMessage()); return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getCode()); } } ``` # 完善异常信息文章中的异常只定义了`code`，具体的异常信息可以写在配置文件中或者保存在数据库中，在捕获到异常之后，找到对应的描述信息返回调用者，增加友好度。 # 完善记录日志以上如果发生了异常，在日志文件中是这样记录的 ``` 10:19:32.024 [http-nio-8080-exec-2] ERROR c.g.e.d.advice.GlobalExceptionAdvice 41 - / by zero ``` 发现记录的行号是在`GlobalExceptionAdvice`类中，并非是代码真实的位置。如果要记录到代码的真实位置可以这样实现 ```java public String getExceptionDetail(Exception e) { StringBuilder stringBuilder = new StringBuilder(); stringBuilder.append(e.getClass() + System.getProperty("line.separator")); stringBuilder.append(e.getLocalizedMessage() + System.getProperty("line.separator")); StackTraceElement[] arr = e.getStackTrace(); for (int i = 0; i < arr.length; i++) { stringBuilder.append(arr[i].toString() + System.getProperty("line.separator")); } return stringBuilder.toString(); } ``` ```java log.error(getExceptionDetail(e)); ``` 根据实际情况选择适合自己的方式 # 完整代码 [Github](https://github.com/lizeze/exception-demo) [Gitee](https://gitee.com/zeze.li/exception-demo)