SpringMVC對異常進行全局處理,並區分對待ajax和普通請求

異常信息應統一進行處理. 程序員開發過程中,應盡量少用try..catch.避免因為catch造成的業務歧義.
而在web開發中,普通的頁面提交動作,和ajax提交動作,處理方式不一樣,因為跳轉后直接顯示響應數據,而ajax是通過error回調函數進行處理.

這里的處理思路,適用springmvc和struts2. 只是叫法不一樣,一個是HandlerExceptionResolver ,一個是exceptioninterceptor.

下面是部分摘要,體現一下思路

首先定義異常攔截器:

@Component
public class MyExceptionHandler implements HandlerExceptionResolver {
    protected Log log = LogFactory.getLog(this.getClass());

    @Override
    public ModelAndView resolveException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex) {
        log.error("異常捕獲", ex);
        String requestURI = request.getRequestURI();
        String fileExtName = StringUtils.getFileExtName(requestURI);
        boolean isajax = "ajax".equals(fileExtName);
        Throwable parseException = parseException(ex);
        return ExceptionHandlerFactory.createExceptionhandler(parseException)
                .resolveException(request, response, handler, parseException, isajax);
    }
　　//這里要獲取到最內層的異常
    private static Throwable parseException(Throwable e){
        Throwable tmp = e;
        int breakPoint = 0;
        while(tmp.getCause()!=null){
            if(tmp.equals(tmp.getCause())){
                break;
            }
            tmp=tmp.getCause();
            breakPoint++;
            if(breakPoint>1000){
                break;
            }
        } 
        return tmp;
    }
}

然后是 ExceptionHandlerFactory 主要是用於生成 異常處理的具體類型

public class ExceptionHandlerFactory {
    
    /**
     *  外掛的自定義處理器,用於外部擴展
     */
    private static  Map<String , ExceptionHandler> handlerList = null;
    
    public static ExceptionHandler createExceptionhandler(Throwable ex){
        //這個是自定義的接口
        ExceptionHandler exceptionHandler=null;
        String packageName=ExceptionHandlerFactory.class.getName().replace(ExceptionHandlerFactory.class.getSimpleName(), "");
        String className = ex.getClass().getSimpleName();
        String classFullName = ex.getClass().getName();
 
        if(handlerList==null){
            handlerList = new HashMap<String, ExceptionHandler>();
        }
        if(handlerList.containsKey(classFullName)){
            return handlerList.get(classFullName);
        }
        
        //能走到這邊,說明自定義的沒有生效,走過之后,下面會將他緩存,也就是說,自定義的優先級永遠大過系統自帶的
        try {
　　　　　　　　//這里查找系統自帶的,按照捕獲的異常名稱+ Handler進行查找,算是簡單約定,因為框架開發中的內置我可以約定,擴展的使用配置文件進行
            exceptionHandler = (ExceptionHandler)Class.forName(packageName+ className+"Handler").newInstance(); 
        } catch (Exception e) { 
            e.printStackTrace();
        }   
        if(exceptionHandler==null){
            exceptionHandler =  new SimpleExceptionHandler();
        } 
        handlerList.put(classFullName, exceptionHandler);
         
        return exceptionHandler;
    }

    public Map<String, ExceptionHandler> getHandlerList() {
        return handlerList;
    }
　　//這里有getset,用於spring注入
    public void setHandlerList(Map<String, ExceptionHandler> handlerList) {
        ExceptionHandlerFactory.handlerList = handlerList;
    }
    
    
    
    
    
    
}

最后書寫一個用於驗證異常的處理類型

public class ConstraintViolationExceptionHandler  extends BaseExceptionHandler{

    @Override
    public Object processException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Throwable ex,
            boolean isajax) {
        ConstraintViolationException e=(ConstraintViolationException)ex;
        Set<ConstraintViolation<?>> constraintViolations = e.getConstraintViolations();
 　　　　　　//ValidateInfo包含當前出錯的字段,錯誤信息,出錯的字段所在的類型,等必要的信息
　　　　　　　// 在ajax特別是ajaxForm的提交中,只要前端約定好了命名規則,就可以根據返回的信息,進行界面提示,比如可渲染成和validate一樣的風格
　　　　　　// 也可以給出一個dialog提示,或者......

         List<ValidateInfo> validateInfos =new ArrayList<ValidateInfo>();
         if(constraintViolations!=null && !constraintViolations.isEmpty()){
            for(ConstraintViolation<?> violation : constraintViolations){
                ValidateInfo info = new ValidateInfo();
                info.setField(violation.getPropertyPath().toString().replaceAll("\\.","_"));
                info.setMessage(violation.getMessage());
                Class<? extends Object> class1 = violation.getRootBean().getClass();
                String simpleName =StringUtils.getSpringName(class1); 
                if(simpleName.indexOf("$pcsubclass")>-1){  //這個判斷是openjpa的代理類型,帶$的不光是代理類型,內部類的名稱同樣有,所以編碼上要約束
                     String[] ss = simpleName.split("\\$");
                     if(ss.length>1){
                         simpleName = ss[ss.length-2];
                         simpleName = simpleName.substring(0,1).toLowerCase()+simpleName.substring(1);
                     }
                }
                
                info.setClassName(simpleName);
                Object ov =violation.getInvalidValue();
                if(ov==null){
                    info.setCurrentValue("");
                }else{
                    info.setCurrentValue(ov.toString());
                }
                
                validateInfos.add(info);
            }
            
         }
        return validateInfos; //返回經過封裝的驗證信息,用於jquery ajax error回調方法進行統一處理
    }
}

而BaseExceptionHandler 只是對最后響應代碼做一個判斷

public abstract class BaseExceptionHandler implements ExceptionHandler{

    /**
     * 用於傳遞到頁面的值
     */
    protected Map<String, Object> data = new HashMap<String, Object>();
    
    /**
     * 寫到輸出流
     */
    protected ModelAndView write(HttpServletRequest request,
            HttpServletResponse response, Object handler, Throwable ex,
            boolean isajax,Object dt){
        int responseCode=500;
        if(ex instanceof BaseRuntimeException){
            responseCode=((BaseRuntimeException)ex).getResponseCode();
        }
        if(ex instanceof ConstraintViolationException){
            responseCode=5001;
        }
        response.setStatus(responseCode);
        if(!isajax){//非ajax,直接跳轉的,這里的是否ajax很簡單,我們約定,ajax請求全部使用.ajax擴展.當然通過httpheader也能,jquery還支持preFilter,可以在這里統一加參數
            ModelAndView modelAndView = new ModelAndView("/error/error");
            modelAndView.addObject("__exception__", ex);
            modelAndView.addAllObjects(data);
            if(dt!=null){
            modelAndView.addObject(dt);
            }
            return modelAndView;
        }
        //這個是封裝的標准返回值模版,包含相應code,錯誤信息和響應數據等字段
        ResultTemplate createFailResult = ResultTemplate.createFailResult(ex.getMessage());
        createFailResult.setData(dt);
        WebUtils.renderJson(createFailResult); 
        return null;
    }

    public abstract Object processException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Throwable ex,
            boolean isajax);
    
    
    @Override
    public ModelAndView resolveException(HttpServletRequest request,
            HttpServletResponse response, Object handler, Throwable ex,
            boolean isajax) { 
        Object d = processException(request,  response,   handler,   ex,  isajax); 
        return write(request,
                  response,   handler,   ex,
                  isajax,d);
    }
    
    
    
}

xml 配置

<bean class="com.core.web.interceptor.exceptionhandler.ExceptionHandlerFactory">
        <property name="handlerList">
                     <map>
                         <entry key="javax.validation.ConstraintViolationException" > <!-- jpa驗證異常,這里可以不配置,系統內置,也可以配置自己的,替換系統自帶的 -->
                          <bean class="com.core.web.interceptor.exceptionhandler.ConstraintViolationExceptionHandler"/> 
                         </entry>
                          
                     </map>
             </property> 
    </bean>