Spring 异常处理

全部以404错误、webapp/templates/error-404.html为例

1.ExceptionResolver

主要方法：resolveException

一共有四种实现类：

1）DefaultHandlerExceptionResolver

将Exception转换为错误码

Exception	Error Code
ConversionNoSupportedException HttpMessageNotWritableException	500
HttpMediaTypeNotAcceptableException	406
HttpMediaTypeNotSupporteException	415
HttpMessageNotReadableException MissingServletParameterException TypeMismatchException	400
HttpRequestMethodNotSupportedException	405
NoSuchHandingMethodException	404

可以在web.xml中配置

<error-page>
    <error-code>404</error-code>
    <location>/templates/error-404.html</location>
</error-page>

也可以重写resolveException方法来处理异常（或者重写handleXXException()方法来处理特定异常）

@Bean
public DefaultHandlerExceptionResolver resolver(){
    return new DefaultHandlerExceptionResolver(){
        @Override
        public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
                ……
         }
    }
}

2）AnnotationMethodHandlerExceptionResolver

对同一个类中的Handler方法抛出的错误进行处理

@ExceptionHandler(NoSuchRequestHandlingMethodException.class)
public ModelAndView handleException(RuntimeException re,HttpRequest request){
    return new ModelAndView("error-404");
}

3）SimpleMappingExceptionResolver

    @Bean
    public SimpleMappingExceptionResolver simpleResolver(){
        SimpleMappingExceptionResolver resolver=new SimpleMappingExceptionResolver();
        resolver.addStatusCode("error-404",404);
        return resolver;
    }

4）ResponseStatusExceptionResolver

    @Bean
    public ResponseStatusExceptionResolver resolver(){
        return new ResponseStatusExceptionResolver(){
            @Override
            protected ModelAndView resolveResponseStatus(ResponseStatus responseStatus, HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
                if(responseStatus.value()== HttpStatus.NOT_FOUND)
                    return new ModelAndView("error-404");
                //对其他错误码继续处理
                ……
            }
        };
    }

需要配合@ResponseStatus注解

2.Spring Boot增加的两种方法：

1）ErrorController：

主要思路：把错误都集中到一个路径下，然后再根据状态码分别处理（有点像Servlet的init()方法集合了所有HTTP请求的处理，但是又分派到各种doXXXX方法分别处理）

@Controller
public class ErrorProcessController implements ErrorController {

    @RequestMapping("/error")
    public String handleError(HttpServletResponse response){
        int statusCode = response.getStatus();
        if(statusCode == 404){
            return "error-404";
        }else{
           //继续对其他错误码进行处理
            ……
        }
    }

    @Override
    public String getErrorPath() {
        return "/error";
    }
}

2）EmbeddedServletContainerCustomizer

    @Bean
    public EmbeddedServletContainerCustomizer containerCustomizer(){
        return container -> {
            ErrorPage page404=new ErrorPage(HttpStatus.NOT_FOUND,"/404");
            container.addErrorPages(page404);
        };
    }

然后再在Controller中对"/404"请求处理，返回"error-404"即可

也可以直接返回"error-404.html"，不过需要放在static目录下

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