# 处理异常

Spring 提供了多种方式将异常转换为响应：

* **特定的 Spring 异常将会自动映射为指定的 HTTP 状态码；**
* **异常上可以添加 @ResponseStatus 注解，从而将其映射为某一个 HTTP 状态码；**
* **在方法上可以添加 @ExceptionHandler 注解，使其用来处理异常。**

## **1. 自动映射**

<mark style="color:blue;">**在默认情况下，Spring 会将自身的一些异常自动转换为合适的状态码。**</mark>

| Spring 异常                               | HTTP 状态码                     |
| --------------------------------------- | ---------------------------- |
| BindException                           | 400 - Bad Request            |
| ConversionNotSupportedException         | 500 - Internal Server Error  |
| HttpMediaTypeNotAcceptableException     | 406 - Not Acceptable         |
| HttpMediaTypeNotSupportedException      | 415 - Unsupported Media Type |
| HttpMessageNotReadableException         | 400 - Bad Request            |
| HttpMessageNotWritableException         | 500 - Internal Server Error  |
| HttpRequestMethodNotSupportedException  | 405 - Method Not Allowed     |
| MethodArgumentNotValidException         | 400 - Bad Request            |
| MissingServletRequestParameterException | 400 - Bad Request            |
| MissingServletRequestPartException      | 400 - Bad Request            |
| NoSuchRequestHandlingMethodException    | 404 - Not Found              |
| TypeMismatchException                   | 400 - Bad Request            |

## **2. 在异常类上添加 @ResponseStatus**

在自定义<mark style="color:blue;">**异常类**</mark>时，可以在类上可以<mark style="color:blue;">**添加 @ResponseStatus 注解**</mark>，从而将其映射为某一个 HTTP 状态码。

```java
@ResponseStatus(
    value = HttpStatus.BAD_REQUEST,
    reason = "参数校验不通过"
)
public class ValidationException extends RuntimeException {
}
```

## **3. @ExceptionHandler**

在 Controller 中增加一个标注了 <mark style="color:blue;">**@ExceptionHandler**</mark> 注解的方法，它会自动处理该控制器中所有方法抛出的指定异常。

```java
@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(ValidationException.class)
public String handleException(ValidationException exception) {
    return exception.getMessage();
}
```

<mark style="color:blue;">**与该 handleException 方法处于同一个 Controller 中的所有方法，当它们抛出 ValidationException 时，其处理逻辑都会委托给该方法进行处理。**</mark>

如果多个控制器类中都会抛出某个特定的异常，那么你可能会发现要在所有的控制器方法中重复相同的 @ExceptionHandler 方法。或者，为了避免重复，我们会<mark style="color:blue;">**创建一个基础的控制器类，所有控制器类要扩展这个类，从而继承通用的 @ExceptionHandler 方法。**</mark>还可以通过控制器通知 ControllerAdvice 来实现统一的异常处理。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://bohans.gitbook.io/ji-chu/spring/basic/spring-mvc/kong-zhi-qi-bian-xie-ji-qiao/chu-li-yi-chang.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.