SpringBoot 错误处理机制与自定义错误处理实现详解

2019-11-26 09:30:48

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【1】SpringBoot的默认错误处理

① 浏览器访问

请求头如下：

② 使用“PostMan”访问

{  "timestamp": 1529479254647,  "status": 404,  "error": "Not Found",  "message": "No message available",  "path": "/aaa1"}

请求头如下：

总结：如果是浏览器访问，则SpringBoot默认返回错误页面；如果是其他客户端访问，则默认返回JSON数据。

【2】默认错误处理原理

SpringBoot默认配置了许多xxxAutoConfiguration，这里我们找ErrorMvcAutoConfiguration。

其注册部分组件如下：

① DefaultErrorAttributes

@Bean@ConditionalOnMissingBean(value = ErrorAttributes.class, search = SearchStrategy.CURRENT)public DefaultErrorAttributes errorAttributes() {  return new DefaultErrorAttributes();}

跟踪其源码如下：

public class DefaultErrorAttributes    implements ErrorAttributes, HandlerExceptionResolver, Ordered {  private static final String ERROR_ATTRIBUTE = DefaultErrorAttributes.class.getName()      + ".ERROR";  @Override  public int getOrder() {    return Ordered.HIGHEST_PRECEDENCE;  }  @Override  public ModelAndView resolveException(HttpServletRequest request,      HttpServletResponse response, Object handler, Exception ex) {    storeErrorAttributes(request, ex);    return null;  }  private void storeErrorAttributes(HttpServletRequest request, Exception ex) {    request.setAttribute(ERROR_ATTRIBUTE, ex);  }  @Override  public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes,      boolean includeStackTrace) {    Map<String, Object> errorAttributes = new LinkedHashMap<String, Object>();    errorAttributes.put("timestamp", new Date());    addStatus(errorAttributes, requestAttributes);    addErrorDetails(errorAttributes, requestAttributes, includeStackTrace);    addPath(errorAttributes, requestAttributes);    return errorAttributes;  }  private void addStatus(Map<String, Object> errorAttributes,      RequestAttributes requestAttributes) {    Integer status = getAttribute(requestAttributes,        "javax.servlet.error.status_code");    if (status == null) {      errorAttributes.put("status", 999);      errorAttributes.put("error", "None");      return;    }    errorAttributes.put("status", status);    try {      errorAttributes.put("error", HttpStatus.valueOf(status).getReasonPhrase());    }    catch (Exception ex) {      // Unable to obtain a reason      errorAttributes.put("error", "Http Status " + status);    }  }  private void addErrorDetails(Map<String, Object> errorAttributes,      RequestAttributes requestAttributes, boolean includeStackTrace) {    Throwable error = getError(requestAttributes);    if (error != null) {      while (error instanceof ServletException && error.getCause() != null) {        error = ((ServletException) error).getCause();      }      errorAttributes.put("exception", error.getClass().getName());      addErrorMessage(errorAttributes, error);      if (includeStackTrace) {        addStackTrace(errorAttributes, error);      }    }    Object message = getAttribute(requestAttributes, "javax.servlet.error.message");    if ((!StringUtils.isEmpty(message) || errorAttributes.get("message") == null)        && !(error instanceof BindingResult)) {      errorAttributes.put("message",          StringUtils.isEmpty(message) ? "No message available" : message);    }  }  private void addErrorMessage(Map<String, Object> errorAttributes, Throwable error) {    BindingResult result = extractBindingResult(error);    if (result == null) {      errorAttributes.put("message", error.getMessage());      return;    }    if (result.getErrorCount() > 0) {      errorAttributes.put("errors", result.getAllErrors());      errorAttributes.put("message",          "Validation failed for object='" + result.getObjectName()              + "'. Error count: " + result.getErrorCount());    }    else {      errorAttributes.put("message", "No errors");    }  }  private BindingResult extractBindingResult(Throwable error) {    if (error instanceof BindingResult) {      return (BindingResult) error;    }    if (error instanceof MethodArgumentNotValidException) {      return ((MethodArgumentNotValidException) error).getBindingResult();    }    return null;  }  private void addStackTrace(Map<String, Object> errorAttributes, Throwable error) {    StringWriter stackTrace = new StringWriter();    error.printStackTrace(new PrintWriter(stackTrace));    stackTrace.flush();    errorAttributes.put("trace", stackTrace.toString());  }  private void addPath(Map<String, Object> errorAttributes,      RequestAttributes requestAttributes) {    String path = getAttribute(requestAttributes, "javax.servlet.error.request_uri");    if (path != null) {      errorAttributes.put("path", path);    }  }  @Override  public Throwable getError(RequestAttributes requestAttributes) {    Throwable exception = getAttribute(requestAttributes, ERROR_ATTRIBUTE);    if (exception == null) {      exception = getAttribute(requestAttributes, "javax.servlet.error.exception");    }    return exception;  }  @SuppressWarnings("unchecked")  private <T> T getAttribute(RequestAttributes requestAttributes, String name) {    return (T) requestAttributes.getAttribute(name, RequestAttributes.SCOPE_REQUEST);  }}

即，填充错误数据！

② BasicErrorController

@Bean@ConditionalOnMissingBean(value = ErrorController.class, search = SearchStrategy.CURRENT)public BasicErrorController basicErrorController(ErrorAttributes errorAttributes) {  return new BasicErrorController(errorAttributes, this.serverProperties.getError(),      this.errorViewResolvers);}

跟踪其源码：

@Controller@RequestMapping("${server.error.path:${error.path:/error}}")public class BasicErrorController extends AbstractErrorController {  //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) {    HttpStatus status = getStatus(request);    Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(        request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));    response.setStatus(status.value());    //去哪个页面作为错误页面；包含页面地址和页面内容    ModelAndView modelAndView = resolveErrorView(request, response, status, model);    return (modelAndView == null ? new ModelAndView("error", model) : modelAndView);  }  //产生json数据，其他客户端来到这个方法处理；  @RequestMapping  @ResponseBody  public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {    Map<String, Object> body = getErrorAttributes(request,        isIncludeStackTrace(request, MediaType.ALL));    HttpStatus status = getStatus(request);    return new ResponseEntity<Map<String, Object>>(body, status);  }  //...}

其中 resolveErrorView(request, response, status, model);方法跟踪如下：

public abstract class AbstractErrorController implements ErrorController {protected ModelAndView resolveErrorView(HttpServletRequest request,      HttpServletResponse response, HttpStatus status, Map<String, Object> model) {      //拿到所有的错误视图解析器    for (ErrorViewResolver resolver : this.errorViewResolvers) {      ModelAndView modelAndView = resolver.resolveErrorView(request, status, model);      if (modelAndView != null) {        return modelAndView;      }    }    return null;  }//...}

③ ErrorPageCustomizer

@Beanpublic ErrorPageCustomizer errorPageCustomizer() {  return new ErrorPageCustomizer(this.serverProperties);}

跟踪其源码：

@Overridepublic void registerErrorPages(ErrorPageRegistry errorPageRegistry) {  ErrorPage errorPage = new ErrorPage(this.properties.getServletPrefix()      + this.properties.getError().getPath());  errorPageRegistry.addErrorPages(errorPage);}//getPath()->go on  /**   * Path of the error controller.   */  @Value("${error.path:/error}")  private String path = "/error";

即，系统出现错误以后来到error请求进行处理（web.xml注册的错误页面规则）。

④ DefaultErrorViewResolver

@Bean@ConditionalOnBean(DispatcherServlet.class)@ConditionalOnMissingBeanpublic DefaultErrorViewResolver conventionErrorViewResolver() {  return new DefaultErrorViewResolver(this.applicationContext,      this.resourceProperties);}

跟踪其源码：

public class DefaultErrorViewResolver implements ErrorViewResolver, Ordered {  private static final Map<Series, String> SERIES_VIEWS;  //错误状态码  static {    Map<Series, String> views = new HashMap<Series, String>();    views.put(Series.CLIENT_ERROR, "4xx");    views.put(Series.SERVER_ERROR, "5xx");    SERIES_VIEWS = Collections.unmodifiableMap(views);  }  //...  @Override  public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status,      Map<String, Object> model) {  // 这里如果没有拿到精确状态码(如404)的视图，则尝试拿4XX(或5XX)的视图    ModelAndView modelAndView = resolve(String.valueOf(status), model);    if (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) {      modelAndView = resolve(SERIES_VIEWS.get(status.series()), model);    }    return modelAndView;  }  private ModelAndView resolve(String viewName, Map<String, Object> model) {    //默认SpringBoot可以去找到一个页面？ error/404||error/4xx    String errorViewName = "error/" + viewName;    //模板引擎可以解析这个页面地址就用模板引擎解析    TemplateAvailabilityProvider provider = this.templateAvailabilityProviders        .getProvider(errorViewName, this.applicationContext);    if (provider != null) {      //模板引擎可用的情况下返回到errorViewName指定的视图地址      return new ModelAndView(errorViewName, model);    }    //模板引擎不可用，就在静态资源文件夹下找errorViewName对应的页面 error/404.html    return resolveResource(errorViewName, model);  }  private ModelAndView resolveResource(String viewName, Map<String, Object> model) {    //从静态资源文件夹下面找错误页面    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;  }

总结如下：

一但系统出现4xx或者5xx之类的错误，ErrorPageCustomizer就会生效（定制错误的响应规则），就会来到/error请求，然后被BasicErrorController处理返回ModelAndView或者JSON。

【3】定制错误响应

① 定制错误响应页面

1）有模板引擎的情况下

error/状态码将错误页面命名为错误状态码.html 放在模板引擎文件夹里面的error文件夹下，发生此状态码的错误就会来到对应的页面。

我们可以使用4xx和5xx作为错误页面的文件名来匹配这种类型的所有错误，精确优先（优先寻找精确的状态码.html）。

如下图所示：

页面能获取的信息；

timestamp：时间戳
status：状态码
error：错误提示
exception：异常对象
message：异常消息
errors：JSR303数据校验的错误都在这里

2）没有模板引擎（模板引擎找不到这个错误页面），静态资源文件夹下找。

3）以上都没有错误页面，就是默认来到SpringBoot默认的错误提示页面。

WebMVCAutoConfiguration源码如下：

@Configuration@ConditionalOnProperty(prefix = "server.error.whitelabel", name = "enabled", matchIfMissing = true)@Conditional(ErrorTemplateMissingCondition.class)protected static class WhitelabelErrorViewConfiguration {  private final SpelView defaultErrorView = new SpelView(      "<html><body><h1>Whitelabel Error Page</h1>"          + "<p>This application has no explicit mapping for /error, so you are seeing this as a fallback.</p>"          + "<div id='created'>${timestamp}</div>"          + "<div>There was an unexpected error (type=${error}, status=${status}).</div>"          + "<div>${message}</div></body></html>");  @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(BeanNameViewResolver.class)  public BeanNameViewResolver beanNameViewResolver() {    BeanNameViewResolver resolver = new BeanNameViewResolver();    resolver.setOrder(Ordered.LOWEST_PRECEDENCE - 10);    return resolver;  }}

② 定制错误响应数据

第一种，使用SpringMVC的异常处理器

@ControllerAdvicepublic class MyExceptionHandler {  //浏览器客户端返回的都是json  @ResponseBody  @ExceptionHandler(UserNotExistException.class)  public Map<String,Object> handleException(Exception e){    Map<String,Object> map = new HashMap<>();    map.put("code","user.notexist");    map.put("message",e.getMessage());    return map;  }}

这样无论浏览器还是PostMan返回的都是JSON！

第二种，转发到/error请求进行自适应效果处理

 @ExceptionHandler(UserNotExistException.class) public String handleException(Exception e, HttpServletRequest request){    Map<String,Object> map = new HashMap<>();    //传入我们自己的错误状态码 4xx 5xx    /**    * Integer statusCode = (Integer) request    .getAttribute("javax.servlet.error.status_code");    */    request.setAttribute("javax.servlet.error.status_code",500);    map.put("code","user.notexist");    map.put("message","用户出错啦");    //转发到/error    return "forward:/error";  }

但是此时没有将自定义 code message传过去！

第三种，注册MyErrorAttributes继承自DefaultErrorAttributes(推荐)

从第【2】部分(默认错误处理原理)中知道错误数据都是通过DefaultErrorAttributes.getErrorAttributes()方法获取，如下所示：

  @Override  public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes,      boolean includeStackTrace) {    Map<String, Object> errorAttributes = new LinkedHashMap<String, Object>();    errorAttributes.put("timestamp", new Date());    addStatus(errorAttributes, requestAttributes);    addErrorDetails(errorAttributes, requestAttributes, includeStackTrace);    addPath(errorAttributes, requestAttributes);    return errorAttributes;  }

我们可以编写一个MyErrorAttributes继承自DefaultErrorAttributes重写其getErrorAttributes方法将我们的错误数据添加进去。

示例如下：

//给容器中加入我们自己定义的ErrorAttributes@Componentpublic class MyErrorAttributes extends DefaultErrorAttributes {  //返回值的map就是页面和json能获取的所有字段  @Override  public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes, boolean includeStackTrace) {    //DefaultErrorAttributes的错误数据    Map<String, Object> map = super.getErrorAttributes(requestAttributes, includeStackTrace);    map.put("company","SpringBoot");    //我们的异常处理器携带的数据    Map<String,Object> ext = (Map<String, Object>) requestAttributes.getAttribute("ext", 0);    map.put("ext",ext);    return map;  }}

异常处理器修改如下：

@ExceptionHandler(UserNotExistException.class)public String handleException(Exception e, HttpServletRequest request){   Map<String,Object> map = new HashMap<>();   //传入我们自己的错误状态码 4xx 5xx   /**   * Integer statusCode = (Integer) request   .getAttribute("javax.servlet.error.status_code");   */   request.setAttribute("javax.servlet.error.status_code",500);   map.put("code","user.notexist");   map.put("message","用户出错啦");  //将自定义错误数据放入request中   request.setAttribute("ext",map);   //转发到/error   return "forward:/error"; }

5xx.html页面代码如下：

//...<main role="main" class="col-md-9 ml-sm-auto col-lg-10 pt-3 px-4">  <h1>status:[[${status}]]</h1>  <h2>timestamp:[[${timestamp}]]</h2>  <h2>exception:[[${exception}]]</h2>  <h2>message:[[${message}]]</h2>  <h2>ext:[[${ext.code}]]</h2>  <h2>ext:[[${ext.message}]]</h2></main>//...

浏览器测试效果如下：