在J2EE项目的开发中,不管是对底层的数据库操作过程,还是业务层的处理过程,还是控制层的处理过程,都不可避免会遇到各种可预知的、不可预知的异常需要处理。每个过程都单独处理异常,系统的代码耦合度高,工作量大且不好统一,维护的工作量也很大。 那么,能不能将所有类型的异常处理从各处理过程解耦出来,这样既保证了相关处理过程的功能较单一,也实现了异常信息的统一处理和维护?答案是肯定的。下面将介绍使用Spring MVC统一处理异常的解决和实现过程。
- 使用Spring MVC提供的SimpleMappingExceptionResolver
- 实现Spring的异常处理接口HandlerExceptionResolver 自定义自己的异常处理器
- 使用@ExceptionHandler注解实现异常处理
(一) SimpleMappingExceptionResolver
使用这种方式具有集成简单、有良好的扩展性、对已有代码没有入侵性等优点,但该方法仅能获取到异常信息,若在出现异常时,对需要获取除异常以外的数据的情况不适用。
1 @Configuration 2 @EnableWebMvc 3 @ComponentScan(basePackages = {"com.balbala.mvc.web"}) 4 public class WebMVCConfig extends WebMvcConfigurerAdapter{ 5 @Bean 6 public SimpleMappingExceptionResolver simpleMappingExceptionResolver() 7 { 8 SimpleMappingExceptionResolver b = new SimpleMappingExceptionResolver(); 9 Properties mappings = new Properties(); 10 mappings.put("org.springframework.web.servlet.PageNotFound", "page-404"); 11 mappings.put("org.springframework.dao.DataAccessException", "data-access"); 12 mappings.put("org.springframework.transaction.TransactionException", "transaction-Failure"); 13 b.setExceptionMappings(mappings); 14 return b; 15 } 16 }
(二) HandlerExceptionResolver
相比第一种来说,HandlerExceptionResolver能准确显示定义的异常处理页面,达到了统一异常处理的目标
1.定义一个类实现HandlerExceptionResolver接口
1 public class GlobalHandlerExceptionResolver implements HandlerExceptionResolver { 2 private static final Logger LOG = LoggerFactory.getLogger(GlobalHandlerExceptionResolver.class); 3 /** 4 * 在这里处理所有得异常信息 5 */ 6 @Override 7 public ModelAndView resolveException(HttpServletRequest req, HttpServletResponse resp, Object o, Exception ex) { 8 ex.printStackTrace(); 9 if (ex instanceof AthenaException) { 10 //AthenaException为一个自定义异常 11 ex.printStackTrace(); 12 printWrite(ex.toString(), resp); 13 return new ModelAndView(); 14 } 15 //RspMsg为一个自定义处理异常信息的类 16 //ResponseCode为一个自定义错误码的接口 17 RspMsg unknownException = null; 18 if (ex instanceof NullPointerException) { 19 unknownException = new RspMsg(ResponseCode.CODE_UNKNOWN, "业务判空异常", null); 20 } else { 21 unknownException = new RspMsg(ResponseCode.CODE_UNKNOWN, ex.getMessage(), null); } 22 printWrite(unknownException.toString(), resp); 23 return new ModelAndView(); 24 } 25 26 /** 27 * 将错误信息添加到response中 28 * 29 * @param msg 30 * @param response 31 * @throws IOException 32 */ 33 public static void printWrite(String msg, HttpServletResponse response) { 34 try { 35 PrintWriter pw = response.getWriter(); 36 pw.write(msg); 37 pw.flush(); 38 pw.close(); 39 } catch (Exception e) { 40 e.printStackTrace(); 41 } 42 } 43 }
这种方式实现的异常处理,可以针对不同的异常和自己定义的异常码进行翻译,然后输出到response中,在前端展示。
(三)@ExceptionHandler
1.首先定义一个父类,实现一些基础的方法
1 public class BaseGlobalExceptionHandler { 2 protected static final Logger logger = null; 3 protected static final String DEFAULT_ERROR_MESSAGE = "系统忙,请稍后再试"; 4 5 protected ModelAndView handleError(HttpServletRequest req, HttpServletResponse rsp, Exception e, String viewName, HttpStatus status) throws Exception { 6 if (AnnotationUtils.findAnnotation(e.getClass(), ResponseStatus.class) != null) 7 throw e; 8 String errorMsg = e instanceof MessageException ? e.getMessage() : DEFAULT_ERROR_MESSAGE; 9 String errorStack = Throwables.getStackTraceAsString(e); 10 11 getLogger().error("Request: {} raised {}", req.getRequestURI(), errorStack); 12 if (Ajax.isAjax(req)) { 13 return handleAjaxError(rsp, errorMsg, status); 14 } 15 return handleViewError(req.getRequestURL().toString(), errorStack, errorMsg, viewName); 16 } 17 18 protected ModelAndView handleViewError(String url, String errorStack, String errorMessage, String viewName) { 19 ModelAndView mav = new ModelAndView(); 20 mav.addObject("exception", errorStack); 21 mav.addObject("url", url); 22 mav.addObject("message", errorMessage); 23 mav.addObject("timestamp", new Date()); 24 mav.setViewName(viewName); 25 return mav; 26 } 27 28 protected ModelAndView handleAjaxError(HttpServletResponse rsp, String errorMessage, HttpStatus status) throws IOException { 29 rsp.setCharacterEncoding("UTF-8"); 30 rsp.setStatus(status.value()); 31 PrintWriter writer = rsp.getWriter(); 32 writer.write(errorMessage); 33 writer.flush(); 34 return null; 35 } 36 37 public Logger getLogger() { 38 return LoggerFactory.getLogger(BaseGlobalExceptionHandler.class); 39 } 40 }
2.针对你需要捕捉的异常实现相对应的处理方式
1 @ControllerAdvice 2 public class GlobalExceptionHandler extends BaseGlobalExceptionHandler { 3 4 //比如404的异常就会被这个方法捕获 5 @ExceptionHandler(NoHandlerFoundException.class) 6 @ResponseStatus(HttpStatus.NOT_FOUND) 7 public ModelAndView handle404Error(HttpServletRequest req, HttpServletResponse rsp, Exception e) throws Exception { 8 return handleError(req, rsp, e, "error-front", HttpStatus.NOT_FOUND); 9 } 10 11 //500的异常会被这个方法捕获 12 @ExceptionHandler(Exception.class) 13 @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR) 14 public ModelAndView handleError(HttpServletRequest req, HttpServletResponse rsp, Exception e) throws Exception { 15 return handleError(req, rsp, e, "error-front", HttpStatus.INTERNAL_SERVER_ERROR); 16 } 17 18 //TODO 你也可以再写一个方法来捕获你的自定义异常 19 //TRY NOW!!! 20 21 @Override 22 public Logger getLogger() { 23 return LoggerFactory.getLogger(GlobalExceptionHandler.class); 24 } 25 26 }
时间: 2024-10-10 10:21:03