【Spring MVC 系列】异常处理，为你的应用加层防护

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
          http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <error-page>
        <error-code>500</error-code>
        <location>/error/500</location>
        <exception-type>java.lang.Exception</exception-type>
    </error-page>
    <error-page>
        <error-code>404</error-code>
        <location>/error/404</location>
    </error-page>
    <error-page>
        <location>/error</location>
    </error-page>
</web-app>

public interface HandlerExceptionResolver {
  @Nullable
  ModelAndView resolveException(
      HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex);
}

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String hello() {
        throw new RuntimeException("处理器发生异常");
    }
    @ExceptionHandler(RuntimeException.class)
    public ModelAndView handleException(RuntimeException e) {
        ModelAndView modelAndView = new ModelAndView("error");
        modelAndView.addObject("exception", e);
        return modelAndView;
    }
}

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(RuntimeException.class)
    public Map<String, Object> handleException(RuntimeException e) {
        Map<String, Object> result = new HashMap<>();
        result.put("message", e.getMessage());
        return result;
    }
}

@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {
  @RequestMapping(produces = MediaType.TEXT_HTML_VALUE)
  public ModelAndView errorHtml(HttpServletRequest request, HttpServletResponse response) {
    HttpStatus status = getStatus(request);
    Map<String, Object> model = Collections
        .unmodifiableMap(getErrorAttributes(request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
    response.setStatus(status.value());
    ModelAndView modelAndView = resolveErrorView(request, response, status, model);
    return (modelAndView != null) ? modelAndView : new ModelAndView("error", model);
  }
}

public class DispatcherServlet extends FrameworkServlet {
  private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
                     @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
                     @Nullable Exception exception) throws Exception {
    boolean errorView = false;
    if (exception != null) {
      // 异常处理
      if (exception instanceof ModelAndViewDefiningException) {
        logger.debug("ModelAndViewDefiningException encountered", exception);
        mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      } else {
        Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
        mv = processHandlerException(request, response, handler, exception);
        errorView = (mv != null);
      }
    }
    // 视图渲染
    if (mv != null && !mv.wasCleared()) {
      render(mv, request, response);
      if (errorView) {
        WebUtils.clearErrorRequestAttributes(request);
      }
    } 
    ... 省略部分代码
  }
}

public class DispatcherServlet extends FrameworkServlet {
  @Nullable
  protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,
                           @Nullable Object handler, Exception ex) throws Exception {
    ModelAndView exMv = null;
    if (this.handlerExceptionResolvers != null) {
      // 使用异常解析器进行异常处理
      for (HandlerExceptionResolver resolver : this.handlerExceptionResolvers) {
        exMv = resolver.resolveException(request, response, handler, ex);
        if (exMv != null) {
          break;
        }
      }
    }
    if (exMv != null) {
      if (exMv.isEmpty()) {
        request.setAttribute(EXCEPTION_ATTRIBUTE, ex);
        return null;
      }
        ... 省略部分代码
      return exMv;
    }
    throw ex;
  }
}