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

1. Springboot 默认的application properties
2. 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"));
   		}
   	};
   }

   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 "";
   	}
   
   }

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。