springboot的错误处理机制以及自定义错误处理

springboot的版本

2.0.2.RELEASE

springboot默认的错误处理机制

默认出错后的效果

• 使用浏览器请求，出错后返回的信息

默认错误页面.png

• 使用postman请求，出错后返回的信息

postman请求的出错提示.png

springboot错误处理的原理

• 在ErrorMvcAutoConfiguration类中，注入了BasicErrorController来处理默认/error的请求

@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class })
// Load before the main WebMvcAutoConfiguration so that the error View is available
@AutoConfigureBefore(WebMvcAutoConfiguration.class)
@EnableConfigurationProperties({ ServerProperties.class, ResourceProperties.class })
public class ErrorMvcAutoConfiguration {
    
    //错误属性的定义
    @Bean
    @ConditionalOnMissingBean(value = ErrorAttributes.class, search = SearchStrategy.CURRENT)
    public DefaultErrorAttributes errorAttributes() {
        return new DefaultErrorAttributes(
                this.serverProperties.getError().isIncludeException());
    }
    
    //处理错误信息的控制逻辑
    @Bean
    @ConditionalOnMissingBean(value = ErrorController.class, search = SearchStrategy.CURRENT)
    public BasicErrorController basicErrorController(ErrorAttributes errorAttributes) {
        return new BasicErrorController(errorAttributes, this.serverProperties.getError(),
                this.errorViewResolvers);
    }
    
    //默认的错误页面
    @Configuration
    @ConditionalOnProperty(prefix = "server.error.whitelabel", name = "enabled", matchIfMissing = true)
    @Conditional(ErrorTemplateMissingCondition.class)
    protected static class WhitelabelErrorViewConfiguration {

        private final SpelView defaultErrorView = new SpelView(
                "
Whitelabel Error Page
"
                        + "
This application has no explicit mapping for /error, so you are seeing this as a fallback.
"
                        + "
${timestamp}
"
                        + "
There was an unexpected error (type=${error}, status=${status}).
"
                        + "
${message}
");

        @Bean(name = "error")
        @ConditionalOnMissingBean(name = "error")
        public View defaultErrorView() {
            return this.defaultErrorView;
        }

        // If the user adds @EnableWebMvc then the bean name view resolver from
        // WebMvcAutoConfiguration disappears, so add it back in to avoid disappointment.
        @Bean
        @ConditionalOnMissingBean
        public BeanNameViewResolver beanNameViewResolver() {
            BeanNameViewResolver resolver = new BeanNameViewResolver();
            resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
            return resolver;
        }

    }
    
}

• BasicErrorController里面处理错误请求的方法

@Controller
//查找配置文件中的server.error.path，如果没有，再从配置文件中查找error.path，如果没有就采用默认的/error
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {
   
    //定义了处理错误信息的默认路径  /error
   private final ErrorProperties errorProperties;
  
    //产生html类型的数据；浏览器发送的请求来到这个方法处理
    @RequestMapping(produces = "text/html")
    public ModelAndView errorHtml(HttpServletRequest request,
            HttpServletResponse response) {
        //获取请求的状态信息
        HttpStatus status = getStatus(request);
        Map model = Collections.unmodifiableMap(getErrorAttributes(
                request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
        response.setStatus(status.value());
        //去寻找具体的页面
        ModelAndView modelAndView = resolveErrorView(request, response, status, model);
        return (modelAndView != null ? modelAndView : new ModelAndView("error", model));
    }
    
    
    //产生json数据，其他客户端来到这个方法处理；
    @RequestMapping
    @ResponseBody
    public ResponseEntity> error(HttpServletRequest request) {
        Map body = getErrorAttributes(request,
                isIncludeStackTrace(request, MediaType.ALL));
        HttpStatus status = getStatus(request);
        return new ResponseEntity<>(body, status);
    }
}

• 寻找错误页面的处理流程

@RequestMapping(produces = "text/html")
public ModelAndView errorHtml(HttpServletRequest request,
      HttpServletResponse response) {
   HttpStatus status = getStatus(request);
   Map model = Collections.unmodifiableMap(getErrorAttributes(
         request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
   response.setStatus(status.value());
   //调用解析方法
   ModelAndView modelAndView = resolveErrorView(request, response, status, model);
   //如果都没有找到，就会采用默认的页面，此页面在ErrorMvcAutoConfiguration也已经注册,WhitelabelErrorViewConfiguration
   return (modelAndView != null ? modelAndView : new ModelAndView("error", model));
}

//调用此方法
protected ModelAndView resolveErrorView(HttpServletRequest request,
            HttpServletResponse response, HttpStatus status, Map model) {
    for (ErrorViewResolver resolver : this.errorViewResolvers) {
        //用视图解析去，是寻找相关页面，没有配置的话，
        //使用org.springframework.boot.autoconfigure.web.servlet.error.DefaultErrorViewResolver
        ModelAndView modelAndView = resolver.resolveErrorView(request, status, model);
        if (modelAndView != null) {
            return modelAndView;
        }
    }
    return null;
}



@Override
public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status,
                                     Map model) {
    //默认去 error/  下面去寻找对应http状态码的页面，例如：404.html  500.html
    ModelAndView modelAndView = resolve(String.valueOf(status), model);
    
    //去寻找 4xx   5xx开头的页面
    if (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) {
        modelAndView = resolve(SERIES_VIEWS.get(status.series()), model);
    }
    return modelAndView;
}

//去error/  路径下寻找页面
private ModelAndView resolve(String viewName, Map model) {
    String errorViewName = "error/" + viewName;
    TemplateAvailabilityProvider provider = this.templateAvailabilityProviders
        .getProvider(errorViewName, this.applicationContext);
    if (provider != null) {
        return new ModelAndView(errorViewName, model);
    }
    return resolveResource(errorViewName, model);
}

//再去classpath:/META-INF/resources/", "classpath:/resources/","classpath:/static/", "classpath:/public/"这些路径下，去寻找对应的状态码的html页面
private ModelAndView resolveResource(String viewName, Map model) {
    for (String location : this.resourceProperties.getStaticLocations()) {
        try {
            Resource resource = this.applicationContext.getResource(location);
            resource = resource.createRelative(viewName + ".html");
            if (resource.exists()) {
                return new ModelAndView(new HtmlResourceView(resource), model);
            }
        }
        catch (Exception ex) {
        }
    }
    return null;
}

• 错误的json数据里面属性的来源

  这里面定义的属性有：

  timestamp：时间戳

  status：状态码

  error：错误提示

  exception：异常对象

  path：路径

  等

  package org.springframework.boot.web.servlet.error;
  /**
   * Default implementation of {@link ErrorAttributes}. Provides the following attributes
   * when possible:
   * 
  
   * 
  timestamp - The time that the errors were extracted
   * 
  status - The status code
   * 
  error - The error reason
   * 
  exception - The class name of the root exception (if configured)
   * 
  message - The exception message
   * 
  errors - Any {@link ObjectError}s from a {@link BindingResult} exception
   * 
  trace - The exception stack trace
   * 
  path - The URL path when the exception was raised
   * 
   *
   * @author Phillip Webb
   * @author Dave Syer
   * @author Stephane Nicoll
   * @author Vedran Pavic
   * @since 2.0.0
   * @see ErrorAttributes
   */
   
  @Order(Ordered.HIGHEST_PRECEDENCE)
  public class DefaultErrorAttributes
        implements ErrorAttributes, HandlerExceptionResolver, Ordered {
  

自定义错误响应

• 可以定义一个我们自己的错误类

  package com.nanc.exception;
  
  public class UserNotExistException extends RuntimeException{
  
     public UserNotExistException(){
        super("异常信息---用户不存在");
     }
  }
  

• 自定义异常处理类

  package com.nanc.controller;
  
  import com.nanc.exception.UserNotExistException;
  import org.springframework.web.bind.annotation.ControllerAdvice;
  import org.springframework.web.bind.annotation.ExceptionHandler;
  
  import javax.servlet.http.HttpServletRequest;
  import java.util.HashMap;
  import java.util.Map;
  
  @ControllerAdvice
  public class MyExceptionHandler {
  
     //这个没有自适应效果（浏览器请求返回页面，其他的就返回json数据）,可以转发到/error就可以自适应了
     //@ResponseBody
     //@ExceptionHandler(UserNotExistException.class)
     //public Map handleException(Exception e) {
     // Map map = new HashMap<>();
     //
     // map.put("code", "user not exist");
     // map.put("message", e.getMessage());
     //
     // return map;
     //}
  
     //@ExceptionHandler(UserNotExistException.class)
     //public String handleException(Exception e) {
     // Map map = new HashMap<>();
     //  //自己定义的数据在返回的数据中无法使用
     // map.put("code", "user not exist");
     // map.put("message", e.getMessage());
     //
     // //转发到/error
     // return "forward:/error";
     //}
  
     @ExceptionHandler(UserNotExistException.class)
     public String handleException(Exception e, HttpServletRequest request) {
        Map map = new HashMap<>();
        //传入我们自己的错误状态码 4xx 5xx，否则就不会进入定制错误页面的解析流程
        /*
         * Integer statusCode = (Integer) request
         .getAttribute("javax.servlet.error.status_code");
         */
        request.setAttribute("javax.servlet.error.status_code", 500);
  
        map.put("code", "user not exist");
        map.put("message", e.getMessage());
        request.setAttribute("ext", map);
  
        //转发到/error
        return "forward:/error";
     }
  
  
  }
  

• 定制自己的一些错误属性

  package com.nanc.component;
  
  import org.springframework.boot.web.servlet.error.DefaultErrorAttributes;
  import org.springframework.stereotype.Component;
  import org.springframework.web.context.request.WebRequest;
  
  import java.util.Map;
  
  //给容器中加入我们自己定义的ErrorAttributes
  @Component
  public class MyErrorAttributes extends DefaultErrorAttributes {
  
     @Override
     public Map getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {
        Map map =  super.getErrorAttributes(webRequest, includeStackTrace);
  
        map.put("company","xxxxx");
  
        //我们的异常处理器携带的数据，这些数据是从MyExceptionHandler中传递过来的
        Map ext = (Map) webRequest.getAttribute("ext", 0);
        map.put("ext",ext);
        return map;
     }
  }
  

• 错误页面

  错误页面.png

   
status:[[${status}]]
   
timestamp:[[${timestamp}]]
   
timestamp:[[${#dates.format(timestamp, 'yyyy-MM-dd HH:mm:ss')}]]
   
exception:[[${exception}]]
   
message:[[${message}]]
   
path:[[${path}]]
   
errors:[[${errors}]]
   
ext:[[${ext.code}]]
   
ext:[[${ext.message}]]

注意事项

如果请求返回的是json数据，时间可能会差8个小时，解决办法，在application.yml添加如下配置

spring:
  mvc:
    date-format: yyyy-MM-dd
  jackson: # 解决差8个小时的问题
    time-zone: GMT+8
    date-format: yyyy-MM-dd HH:mm:ss