@Component
public class LoginIntercepetor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 判斷用戶登錄
        HttpSession session = request.getSession(false);
        if(session!=null && session.getAttribute(ApplicationVariable.SESSION_USERINFO_KEY)!=null){
            // 用戶已經(jīng)登錄
            return true;
        }
        // 當(dāng)代碼執(zhí)行到此處說(shuō)明用戶未登錄
        response.sendRedirect("/login.html");
        return false;
    }
}

@Configuration
public class MyConfig implements WebMvcConfigurer {
    @Autowired
    private LoginInterceptor loginInterceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(loginInterceptor)
                .addPathPatterns("/**") //攔截所有的URL
                .excludePathPatterns("/user/login") // 排除 url /user/login 不攔截
                .excludePathPatterns("/user/reg") // 排除 url /user/login 不攔截
        ;
    }
}

@ControllerAdvice
@ResponseBody
public class MyExceptionAdvice {
}

@ExceptionHandler(NullPointerException.class)
public HashMap<String,Object> dpNullPointerException(NullPointerException e){
        HashMap<String,Object> result = new HashMap<>();
        result.put("code",-1);
        result.put("msg","空指針: "+e.getMessage());
        result.put("data",null);
        return result;
        }

@ExceptionHandler(Exception.class)
    public HashMap<String,Object> doException(Exception e){
        HashMap<String,Object> result = new HashMap<>();
        result.put("code",-1);
        result.put("msg","Exception: "+e.getMessage());
        result.put("data",null);
        return result;
    }

@ControllerAdvice
public class MyResponseAdvice implements ResponseBodyAdvice {
    @Autowired
    ObjectMapper objectMapper;
    /**
     * 是否執(zhí)行 beforeBodyWrite 方法,true=執(zhí)行 重寫(xiě)返回結(jié)果,false=不執(zhí)行
     *
     * @param returnType
     * @param converterType
     * @return
     */
    @Override
    public boolean supports(MethodParameter returnType, Class converterType) {
        return true;
    }
    /**
     * 在返回?cái)?shù)據(jù)之前進(jìn)行數(shù)據(jù)重寫(xiě)
     *
     * @param body     原始返回值
     * @param returnType
     * @param selectedContentType
     * @param selectedConverterType
     * @param request
     * @param response
     * @return
     */
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
        //定義一個(gè)標(biāo)準(zhǔn)的返回格式
        //Hash<String,Object> code,msg,data
        if(body instanceof HashMap){
            return body;
        }
        // 重寫(xiě)返回結(jié)果,讓其返回一個(gè)統(tǒng)一的數(shù)據(jù)格式
        HashMap<String,Object> result = new HashMap<>();
        result.put("code",200);
        result.put("msg","");
        result.put("data",body);
        if(body instanceof String){
            // 返回一個(gè) String 字符串
            try {
                objectMapper.writeValueAsString(result);
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
            return result;
        }
        return result;
    }
}