簡單的實現登錄攔截及統一異常處理（自定義異常）

webmvc配置類：

@Configuration
public class WebMvcConfig extends WebMvcConfigurationSupport{

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
        .addPathPatterns("/**")
        .excludePathPatterns("/user/login")；
    }
}

註：registry.addInterceptor(攔截器類對象).addPathPatterns("需要攔截的請求路徑").excludePathPatterns("可以放行的請求路徑");

攔截器類，這裡為登錄攔截

public class LoginInterceptor implements HandlerInterceptor{

    @Override
    public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
            throws Exception {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
            throws Exception {
        // TODO Auto-generated method stub
        
    }

    @Override
    public boolean preHandle(HttpServletRequest hServletRequest, HttpServletResponse hServletResponse, Object object) throws Exception {
        // 案例採用session存儲登錄用戶，所以從session獲取登錄用戶
　　　　 HttpSession session = hServletRequest.getSession();
        TUser tUser=(TUser)session.getAttribute("user");
        // 判斷session里是否能取出用戶
        if(tUser==null) {
            returnErrorMessage(hServletResponse, "當前操作需要先進行用戶登錄");
            return false;
        }
        return true;
    }

    private void returnErrorMessage(HttpServletResponse response, String errorMessage) throws IOException {
        response.setCharacterEncoding("utf-8");
        Map<String, Object> var=new HashMap<>();
        var.put("success", false);
        var.put("errorMessage", errorMessage);
        response.setContentType("application/json");
        PrintWriter out = response.getWriter();
        ObjectMapper mapper = new ObjectMapper();
        String jsonOfRST =mapper.writeValueAsString(var);
        out.print(jsonOfRST);
        out.flush();
    }
}

到這裡實現了簡單的登錄攔截，但是上面通過response對象獲取的輸出流來寫入錯誤信息，下麵採用自定義異常來處理

異常類

public class UnloggedException extends RuntimeException{
    private static final long serialVersionUID = 181074719716690931L;
    
    public UnloggedException() {
        super("當前操作需要先進行登錄");
    }
}

修改攔截器類的preHandle方法，於是returnErrorMessage方法可以去掉了

@Override
    public boolean preHandle(HttpServletRequest hServletRequest, HttpServletResponse hServletResponse, Object object) throws Exception {
        HttpSession session = hServletRequest.getSession();
        TUser tUser=(TUser)session.getAttribute("user");
        if(tUser==null) {
            throw new UnloggedException();
        }
        return true;
    }

最後配置異常處理類

@ControllerAdvice
@ResponseBody
public class GlobalExceptionHandler {
    @ExceptionHandler
    public JSONObject handleException(Exception e) {
        return ActionHelper.responseFailed(e.getMessage());
    }
}

上面的返回值及ActionHelper為我使用的返回工具類，依賴為com.alibaba的fastjson，版本參考1.2.49。

可以根據實際情況修改返回方式及返回值。

此後所有的異常，都可以通過自定義異常的方式，交由異常處理類來進行處理，返回結果。