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 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> error404(HttpServletRequest request) {
        Map body = getErrorAttributes(request,
                isIncludeStackTrace(request, MediaType.TEXT_HTML));
        HttpStatus status = getStatus(request);
        return new ResponseEntity>(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 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> error500(HttpServletRequest request) {
        Map body = getErrorAttributes(request,
                isIncludeStackTrace(request, MediaType.TEXT_HTML));
        HttpStatus status = getStatus(request);
        return new ResponseEntity>(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 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。