Springboot自定义异常处理

背景

Springboot 默认把异常的处理集中到一个ModelAndView中了，但项目的实际过程中，这样做，并不能满足我们的要求。具体的自定义异常的处理，参看以下

前提

Springboot
默认的application properties
Spring Boot异常处理详解

具体实现

如果仔细看完Spring boot的异常处理详解，并且研究过源码后，我觉得具体的实现可以不用看了。。。 

重写定义错误页面的url，默认只有一个/error

@Bean
public EmbeddedServletContainerCustomizer containerCustomizer(){
return new EmbeddedServletContainerCustomizer(){
@Override
public void customize(ConfigurableEmbeddedServletContainer container) {
container.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/error/404"));
container.addErrorPages(new ErrorPage(HttpStatus.INTERNAL_SERVER_ERROR, "/error/500"));
container.addErrorPages(new ErrorPage(java.lang.Throwable.class,"/error/500"));
}
};
}

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重写通过实现ErrorController，重写BasicErrorController的功能实现

**
* 重写BasicErrorController,主要负责系统的异常页面的处理以及错误信息的显示
* @see org.springframework.boot.autoconfigure.web.BasicErrorController
* @see org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration
*
* @author Jonathan
* @version 2016/5/31 11:22
* @since JDK 7.0+
*/
@Controller
@RequestMapping(value = "error")
@EnableConfigurationProperties({ServerProperties.class})
public class ExceptionController implements ErrorController {

private ErrorAttributes errorAttributes;

@Autowired
private ServerProperties serverProperties;

/**
* 初始化ExceptionController
* @param errorAttributes
*/
@Autowired
public ExceptionController(ErrorAttributes errorAttributes) {
Assert.notNull(errorAttributes, "ErrorAttributes must not be null");
this.errorAttributes = errorAttributes;
}

/**
* 定义404的ModelAndView
* @param request
* @param response
* @return
*/
@RequestMapping(produces = "text/html",value = "404")
public ModelAndView errorHtml404(HttpServletRequest request,
HttpServletResponse response) {
response.setStatus(getStatus(request).value());
Map<String, Object> model = getErrorAttributes(request,
isIncludeStackTrace(request, MediaType.TEXT_HTML));
return new ModelAndView("error/404", model);
}

/**
* 定义404的JSON数据
* @param request
* @return
*/
@RequestMapping(value = "404")
@ResponseBody
public ResponseEntity<Map<String, Object>> error404(HttpServletRequest request) {
Map<String, Object> body = getErrorAttributes(request,
isIncludeStackTrace(request, MediaType.TEXT_HTML));
HttpStatus status = getStatus(request);
return new ResponseEntity<Map<String, Object>>(body, status);
}

/**
* 定义500的ModelAndView
* @param request
* @param response
* @return
*/
@RequestMapping(produces = "text/html",value = "500")
public ModelAndView errorHtml500(HttpServletRequest request,
HttpServletResponse response) {
response.setStatus(getStatus(request).value());
Map<String, Object> model = getErrorAttributes(request,
isIncludeStackTrace(request, MediaType.TEXT_HTML));
return new ModelAndView("error/500", model);
}

/**
* 定义500的错误JSON信息
* @param request
* @return
*/
@RequestMapping(value = "500")
@ResponseBody
public ResponseEntity<Map<String, Object>> error500(HttpServletRequest request) {
Map<String, Object> body = getErrorAttributes(request,
isIncludeStackTrace(request, MediaType.TEXT_HTML));
HttpStatus status = getStatus(request);
return new ResponseEntity<Map<String, Object>>(body, status);
}

/**
* Determine if the stacktrace attribute should be included.
* @param request the source request
* @param produces the media type produced (or {@code MediaType.ALL})
* @return if the stacktrace attribute should be included
*/
protected boolean isIncludeStackTrace(HttpServletRequest request,
MediaType produces) {
ErrorProperties.IncludeStacktrace include = this.serverProperties.getError().getIncludeStacktrace();
if (include == ErrorProperties.IncludeStacktrace.ALWAYS) {
return true;
}
if (include == ErrorProperties.IncludeStacktrace.ON_TRACE_PARAM) {
return getTraceParameter(request);
}
return false;
}

/**
* 获取错误的信息
* @param request
* @param includeStackTrace
* @return
*/
private Map<String, Object> getErrorAttributes(HttpServletRequest request,
boolean includeStackTrace) {
RequestAttributes requestAttributes = new ServletRequestAttributes(request);
return this.errorAttributes.getErrorAttributes(requestAttributes,
includeStackTrace);
}

/**
* 是否包含trace
* @param request
* @return
*/
private boolean getTraceParameter(HttpServletRequest request) {
String parameter = request.getParameter("trace");
if (parameter == null) {
return false;
}
return !"false".equals(parameter.toLowerCase());
}

/**
* 获取错误编码
* @param request
* @return
*/
private HttpStatus getStatus(HttpServletRequest request) {
Integer statusCode = (Integer) request
.getAttribute("javax.servlet.error.status_code");
if (statusCode == null) {
return HttpStatus.INTERNAL_SERVER_ERROR;
}
try {
return HttpStatus.valueOf(statusCode);
}
catch (Exception ex) {
return HttpStatus.INTERNAL_SERVER_ERROR;
}
}

/**
* 实现错误路径,暂时无用
* @see ExceptionMvcAutoConfiguration#containerCustomizer()
* @return
*/
@Override
public String getErrorPath() {
return "";
}

}

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总结

第一步，通过定义containerCustomizer,重写定义了异常处理对应的视图。目前定义了404和500，可以继续扩展。 

第二步，重写BasicErrorController,当然可以直接定义一个普通的controller类，直接实现第一步定义的视图的方法。重写的目的是重用ErrorAttributes。这样在页面，直接可以获取到status,message,exception,trace等内容。 

如果仅仅是把异常处理的视图作为静态页面，不需要看到异常信息内容的话，直接第一步后，再定义error/404，error/500等静态视图即可。

ErrorController根据Accept头的内容，输出不同格式的错误响应。比如针对浏览器的请求生成html页面，针对其它请求生成json格式的返回

以上两步的操作，比网上流传的更能实现自定义化。