SpringBoot 错误处理机制与自定义错误处理实现详解

SpringBoot 错误处理机制与自定义错误处理实现详解

【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 getErrorAttributes(RequestAttributes requestAttributes,

boolean includeStackTrace) {

Map errorAttributes = new LinkedHashMap();

errorAttributes.put("timestamp", new Date());

addStatus(errorAttributes, requestAttributes);

addErrorDetails(errorAttributes, requestAttributes, includeStackTrace);

addPath(errorAttributes, requestAttributes);

return errorAttributes;

}

private void addStatus(Map 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 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 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 errorAttributes, Throwable error) {

StringWriter stackTrace = new StringWriter();

error.printStackTrace(new PrintWriter(stackTrace));

stackTrace.flush();

errorAttributes.put("trace", stackTrace.toString());

}

private void addPath(Map 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 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, seUIowVWVarch = 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 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 body = getErrorAttributes(request,

isIncludeStackTrace(request, MediaType.ALL));

HttpStatus status = getStatus(request);

return new ResponseEntity

}

//...

}

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 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

@Bean

public ErrorPageCustomizer errorPageCustomizer() {

return new ErrorPageCustomizer(this.serverProperties);

}

跟踪其源码：UIowVWV

@Override

public 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)

@ConditionalOnMissingBean

public 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_VIEWS;

//错误状态码

static {

Map views = new HashMap();

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 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);

ifUIowVWV (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) {

modelAndView = resolve(SERIES_VIEWS.get(status.series()), model);

}

return modelAndView;

}

private ModelAndView resolve(String viewName, Map 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 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(

"

+ "

This application has no explicit mapping for /error, so you are seeing this as a fallback.

+ "

+ "

+ "

@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

@ControllerAdvice

public class MyExceptionHandler {

//浏览器客户端返回的都是json

@ResponseBody

@ExceptionHandler(UserNotExistException.class)

public Map handleException(Exception e){

Map 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 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 getErrorAttributes(RequestAttributes requestAttributes,

boolean includeStackTrace) {

Map errorAttributes = new LinkedHashMap();

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

@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

@Override

public Map getErrorAttributes(RequestAttributes requestAttributes, boolean includeStackTrace) {

//DefaultErrorAttributes的错误数据

Map map = super.getErrorAttributes(requestAttributes, includeStackTrace);

map.put("company","SpringBoot");

//我们的异常处理器携带的数据

Map ext = (Map) 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 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：

//...

//...

浏览器测试效果如下：

Postman测试效果如下：

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