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Lz_蚂蚱

园龄：5年3个月粉丝：17关注：6

7.错误处理机制

目录

SpringBoot默认的错误处理机制

  • 浏览器，返回一个默认的错误页面

浏览器发送请求的请求头：

  • 其他客户端，默认响应一个json数据

错误处理机制原理

源码参照 ErrorMvcAutoConfiguration错误处理的自动配置类，给容器中添加了以下组件。

  • DefaultErrorAttributes
  • BasicErrorController
  • ErrorPageCustomizer
  • DefaultErrorViewResolver

步骤：

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；就会被BasicErrorController处理；

ErrorPageCustomizer

public class ErrorMvcAutoConfiguration {
    private static class ErrorPageCustomizer implements ErrorPageRegistrar, Ordered {
 
        private final ServerProperties properties;
 
        protected ErrorPageCustomizer(ServerProperties properties) {
            this.properties = properties;
        }
 
        // 注册错误响应页面
        @Override
        public void registerErrorPages(ErrorPageRegistry errorPageRegistry) {
            ErrorPage errorPage = new ErrorPage(this.properties.getServletPrefix()
                                                // 获取错误页面请求路径
                                                + this.properties.getError().getPath());
            errorPageRegistry.addErrorPages(errorPage);
        }
 
        @Override
        public int getOrder() {
            return 0;
        }
 
    }
}
public class ErrorProperties {
 
    /**
     * Path of the error controller.
     */
    @Value("${error.path:/error}")
    private String path = "/error";
 
    /**
     * When to include a "stacktrace" attribute.
     */
    private IncludeStacktrace includeStacktrace = IncludeStacktrace.NEVER;
 
    public String getPath() {
        return this.path;
    }
}
public class ErrorMvcAutoConfiguration {
    @Bean
    @ConditionalOnMissingBean(value = ErrorController.class, search = SearchStrategy.CURRENT)
    public BasicErrorController basicErrorController(ErrorAttributes errorAttributes) {
        return new BasicErrorController(errorAttributes, this.serverProperties.getError(),
                                        this.errorViewResolvers);
    }
}

BasicErrorController：处理默认/error请求

@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);
        // getErrorAttributes() 获取model
        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);
    }
}

DefaultErrorAttributes

public abstract class AbstractErrorController implements ErrorController {
    protected Map<String, Object> getErrorAttributes(HttpServletRequest request,
                                                     boolean includeStackTrace) {
 
        RequestAttributes requestAttributes = new ServletRequestAttributes(request);
        return this.errorAttributes.getErrorAttributes(requestAttributes,
                                                       includeStackTrace);
    }
}

帮我们在页面共享信息

@Order(Ordered.HIGHEST_PRECEDENCE)
public class DefaultErrorAttributes implements ErrorAttributes, HandlerExceptionResolver, Ordered {
 
        @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;
    }
}

DefaultErrorAttributes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

视图解析

public abstract class AbstractErrorController implements ErrorController {
    protected ModelAndView resolveErrorView(HttpServletRequest request,
                                            HttpServletResponse response, HttpStatus status, Map<String, Object> model) {
 
        //所有的异常视图解析器ErrorViewResolver得到ModelAndView
        for (ErrorViewResolver resolver : this.errorViewResolvers) {
            // 响应页面是由DefaultErrorViewResolver解析得到的
            ModelAndView modelAndView = resolver.resolveErrorView(request, status, model);
            if (modelAndView != null) {
                return modelAndView;
            }
        }
        return null;
    }
}

DefaultErrorViewResolver

public class DefaultErrorViewResolver implements ErrorViewResolver, Ordered {
    private static final Map<Series, String> SERIES_VIEWS;
 
    static {
        Map<Series, String> views = new HashMap<Series, String>();
        views.put(Series.CLIENT_ERROR, "4xx"); // 客户端错误用4xx
        views.put(Series.SERVER_ERROR, "5xx"); // 服务端错误用5xx
        SERIES_VIEWS = Collections.unmodifiableMap(views);
    }
 
    @Override
    public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status,
                                         Map<String, Object> model) {
        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，viewName就是上面传入的状态码：error/404
        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) {
        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;
    }
}

错误页面处理过程：

1、在有模板引擎的情况下，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，当发生此状态码的错误就会来到 对应的页面；

当4xx错误码页面很多，每个错误码写一个错误页面不方便，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）。

2、没有模板引擎（模板引擎找不到这个错误页面），在静态资源static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；

@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {
    @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());
		ModelAndView modelAndView = resolveErrorView(request, response, status, model);
                // 当modelAndView为null，使用error视图名的视图对象
		return (modelAndView == null ? new ModelAndView("error", model) : modelAndView);
	}
}
public class ErrorMvcAutoConfiguration {
    @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>");
 
        // 名称为 error的bean
        @Bean(name = "error")
        @ConditionalOnMissingBean(name = "error")
        public View defaultErrorView() {
            return this.defaultErrorView;
        }
    }
}

默认的视图defaultErrorView：

自定义错误json数据响应

方式一：自定义异常处理&返回定制json数据

@ControllerAdvice
public class MyExceptionHandler {
 
    @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;
    }
}

以上全局异常处理方式，没有自适应效果，浏览器与客户端返回的都是json数据。根据不同客户端返回不同结果方式如下。

方式二：转发到 /error进行自适应响应效果处理

@ControllerAdvice
public class MyExceptionHandler { 
    @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，否则就不会进入定制错误页面的解析流程
        request.setAttribute("javax.servlet.error.status_code",500);
        map.put("code","user.notexist");
        map.put("message", e.getMessage());
        //转发到 /error
        return "forward:/error";
    }
}

上面出现错误会显式自定义错误页面，但是展示的错误信息不是我们定制的map.put("message", e.getMessage());错误信息，将我们的定制数据携带出去，需要在出现错误以后，会来到 /error请求，会被BasicErrorController处理，响应出去可以获取的数据是由getErrorAttributes得到的（是AbstractErrorController（ErrorController）规定的方法）；

处理方式：

  • 办法1：

完全来编写一个ErrorController的实现类【或者是编写AbstractErrorController的子类】，放在容器中；

  • 办法2：(推荐)

页面上能用的数据，或者是json返回能用的数据都是通过errorAttributes.getErrorAttributes得到；容器中DefaultErrorAttributes.getErrorAttributes()；默认进行数据处理的；

@ControllerAdvice
public class MyExceptionHandler { 
    @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，否则就不会进入定制错误页面的解析流程
        request.setAttribute("javax.servlet.error.status_code",500);
        map.put("code","user.notexist");
        map.put("message", e.getMessage());
        // 自定义扩展数据放在request域中
        request.setAttribute("ext", map);
        
        return "forward:/error";
    }
}

自定义ErrorAttributes

//给容器中加入我们自己定义的ErrorAttributes
@Component
public class MyErrorAttributes extends DefaultErrorAttributes {
 
    /*
    * 返回值的Map就是页面和json能获取的所有字段
    * RequestAttributes就是包装的Request
    */
    @Override
    public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes, boolean includeStackTrace) {
        Map<String, Object> map = super.getErrorAttributes(requestAttributes, includeStackTrace);
        map.put("company","hguo");
        // RequestAttributes.SCOPE_REQUEST 代表从request域中获取。获取异常处理器携带的数据
        Map<String, Object> ext = (Map<String, Object>) requestAttributes.getAttribute("ext", RequestAttributes.SCOPE_REQUEST);
        map.put("ext", ext);
        return map;
    }
}

最终的效果：响应是自适应的，可以通过定制ErrorAttributes改变需要返回的内容。

posted @   Lz_蚂蚱  阅读(32)  评论(0)  编辑  收藏  举报
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