private ModelAndView resolve(String viewName, Map<String, Object> model) {
	// 定義視圖名，這里我們可以確定視圖名：error/錯(cuò)誤碼，例如：error/404，
    String errorViewName = "error/" + viewName;
    // 這里結(jié)合上面的errorViewName，其實(shí)就是在template目錄下的error目錄進(jìn)行查找
    // 我們默認(rèn)情況下是沒(méi)有error目錄，這里的provide最終值為null，代碼較多就不一一展示，有興趣的可以跟下去
    TemplateAvailabilityProvider provider = this.templateAvailabilityProviders.getProvider(errorViewName, this.applicationContext);
    // 根據(jù)判定，這里會(huì)接著調(diào)用下面的resolveResource方法
    return provider != null ? new ModelAndView(errorViewName, model) : this.resolveResource(errorViewName, model);
}
private ModelAndView resolveResource(String viewName, Map<String, Object> model) {
	//  getStaticLocations()獲取的是靜態(tài)資源路徑："classpath:/META-INF/resources/", "classpath:/resources/","classpath:/static/", "classpath:/public/"
    String[] var3 = this.resourceProperties.getStaticLocations();
    int var4 = var3.length;
	// 遍歷上面的4個(gè)靜態(tài)資源路徑
    for(int var5 = 0; var5 < var4; ++var5) {
        String location = var3[var5];
        try {
            Resource resource = this.applicationContext.getResource(location);
            // 創(chuàng)建resource對(duì)象，例如error/404.html
            resource = resource.createRelative(viewName + ".html");
            // 查找在對(duì)應(yīng)靜態(tài)資源目錄下是否有上面的這個(gè)資源對(duì)象，有就創(chuàng)建視圖對(duì)象
            if (resource.exists()) {
                return new ModelAndView(new DefaultErrorViewResolver.HtmlResourceView(resource), model);
            }
        } catch (Exception var8) {
            ;
        }
    }
	// 都沒(méi)找到就返回null，默認(rèn)情況下是不存在error目錄的，所以這里最終返回null
    return null;
}

static {
    Map<Series, String> views = new EnumMap(Series.class);
    views.put(Series.CLIENT_ERROR, "4xx");
    views.put(Series.SERVER_ERROR, "5xx");
    SERIES_VIEWS = Collections.unmodifiableMap(views);
}

 public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status, Map<String, Object> model) {
 		// 按狀態(tài)碼精確查找
        ModelAndView modelAndView = this.resolve(String.valueOf(status.value()), model);
        // 若精確查找未找到再來(lái)模糊查找
        // status.series()方法可以自己看一下，就是在獲取錯(cuò)誤碼的首位
        if (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) {
            modelAndView = this.resolve((String)SERIES_VIEWS.get(status.series()), model);
        }
        return modelAndView;
    }

    public ModelAndView errorHtml(HttpServletRequest request, HttpServletResponse response) {
        HttpStatus status = this.getStatus(request);
        Map<String, Object> model = Collections.unmodifiableMap(this.getErrorAttributes(request, this.isIncludeStackTrace(request, MediaType.TEXT_HTML)));
        response.setStatus(status.value());
        ModelAndView modelAndView = this.resolveErrorView(request, response, status, model);
        return modelAndView != null ? modelAndView : new ModelAndView("error", model);
    }
    @RequestMapping
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        Map<String, Object> body = this.getErrorAttributes(request, this.isIncludeStackTrace(request, MediaType.ALL));
        HttpStatus status = this.getStatus(request);
        return new ResponseEntity(body, status);
    }

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

public class MyException extends RuntimeException {
    
    public MyException() {
        super("發(fā)生異常了");
    }
}

@ResponseBody
@RequestMapping("/hello")
public String hello(@RequestParam("username") String username){
	// 當(dāng)username值為aaa是拋出異常
    if(username.equals("aaa")){
        throw new MyException();
    }
    return "hello";
}

@ControllerAdvice
public class ExceptionController {
	  @ExceptionHandler(MyException.class)
	  public String f(HttpServletRequest request){
	      // 這里要更改狀態(tài)碼，前面訪問(wèn)路徑是沒(méi)有問(wèn)題的，所以狀態(tài)碼為200
	      // 若想要進(jìn)入springboot錯(cuò)誤處理流程，必須重設(shè)狀態(tài)碼
	      // 并且其key值為：javax.servlet.error.status_code
	      request.setAttribute("javax.servlet.error.status_code",500);
	      // 這里可以添加信息到request中，到后面的取出添加到map中
	      request.setAttribute("data","我的錯(cuò)誤消息");
	      // 轉(zhuǎn)發(fā)到 /error請(qǐng)求，交給springboot處理
	      return "forward:/error";
	  }
}

// 注意，給類(lèi)必須添加到容器中，否則不生效
// 添加后將會(huì)覆蓋原有的DefaultErrorAttributes，采用我們自己的MyErrorAtribute
@Component
public class MyErrorAtribute extends DefaultErrorAttributes {
    @Override
    public Map<String, Object> getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {
        // 獲取包含錯(cuò)誤信息的map
        Map<String, Object> map = super.getErrorAttributes(webRequest, includeStackTrace);
        // 添加自己的錯(cuò)誤數(shù)據(jù)
        map.put("company","lr");
        //獲取轉(zhuǎn)發(fā)過(guò)來(lái)時(shí)添加的數(shù)據(jù)
        // 第二個(gè)參數(shù)表示在哪個(gè)域中獲取，0：request，1：session
        String data = (String)webRequest.getAttribute("data", 0);
        map.put("data",data); // 添加到map
        return map;
    }
}