详解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

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。希望对大家的学习有所帮助，也希望大家多多支持我们。