Controller層方法參數自動注入用戶信息

有時候我們要在controller層每個方法中判斷用戶是否已經登錄了，假如一個一個去判斷的話會很繁瑣。可以采用HandlerMethodArgumentResolver來進行參數自動注入

1 自定義參數解析類UserArgumentResolver ，並將其注入到了argumentResolvers中，注入失敗會拋出自定義異常

@Configuration
public class WebConfig  extends WebMvcConfigurerAdapter{


    @Autowired
    UserArgumentResolver userArgumentResolver;
    

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        //注入自定義參數解析器
        argumentResolvers.add(userArgumentResolver);
    }
    

}

@Service
public class UserArgumentResolver implements HandlerMethodArgumentResolver {

    @Autowired
    MiaoshaUserService userService;

    //只解析方法中參數類型是MiaoshaUser的參數
    public boolean supportsParameter(MethodParameter parameter) {
        Class<?> clazz = parameter.getParameterType();
        return clazz== MiaoshaUser.class;
    }

    //從cookie或者請求參數中獲取token，然后通過token獲取MiaoshaUser對象，
    // 如果獲取不到MiaoshaUser對象，拋出異常，然后被GlobalExceptionHandler捕獲異常，返回給前端
    //如果可以獲取到MiaoshaUser對象，controller方法中的MiaoshaUser類型的參數就被注入值了
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
                                  NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);

        String paramToken = request.getParameter(MiaoshaUserService.COOKI_NAME_TOKEN);
        String cookieToken = getCookieValue(request, MiaoshaUserService.COOKI_NAME_TOKEN);
        if(StringUtils.isEmpty(cookieToken) && StringUtils.isEmpty(paramToken)) {
            throw new GlobalException(CodeMsg.SESSION_ERROR);
        }
        String token = StringUtils.isEmpty(paramToken)?cookieToken:paramToken;
        return userService.getByToken(response, token);
    }

    private String getCookieValue(HttpServletRequest request, String cookiName) {
        Cookie[]  cookies = request.getCookies();
        if(cookies != null && cookies.length > 0 ){
            for(Cookie cookie : cookies) {
                if(cookie.getName().equals(cookiName)) {
                    return cookie.getValue();
                }
            }
        }
        return null;
    }


}

2 全局異常捕獲

public class GlobalException extends RuntimeException{

    private static final long serialVersionUID = 1L;
    
    private CodeMsg cm;
    
    public GlobalException(CodeMsg cm) {
        super(cm.toString());
        this.cm = cm;
    }

    public CodeMsg getCm() {
        return cm;
    }

}

@ControllerAdvice
@ResponseBody
public class GlobalExceptionHandler {

    @ExceptionHandler(value=Exception.class)
    public Result<String> exceptionHandler(HttpServletRequest request, HttpServletResponse response ,Exception e){
        e.printStackTrace();
        if(e instanceof GlobalException) {
            GlobalException ex = (GlobalException)e;
            response.setCharacterEncoding("UTF-8");
            response.setContentType("application/json; charset=utf-8");
            PrintWriter out = null;
            try {
                out = response.getWriter();
                out.append(JSON.toJSONString(Result.error(ex.getCm())));
            } catch (Exception exx) {
                exx.printStackTrace();
            } finally {
                if (out != null) {
                    out.close();
                }
            }
            return null;
        }else if(e instanceof BindException) {
            BindException ex = (BindException)e;
            List<ObjectError> errors = ex.getAllErrors();
            ObjectError error = errors.get(0);
            String msg = error.getDefaultMessage();
            return Result.error(CodeMsg.BIND_ERROR.fillArgs(msg));
        }else {
            return Result.error(CodeMsg.SERVER_ERROR);
        }
    }
}

3 controller層中的方法 MiaoshaUser是被自動注入的。如果注入失敗會拋出異常，把異常返回給前端

@Controller
@RequestMapping("/goods")
public class GoodsController {

    @RequestMapping(value="/to_list")
    @ResponseBody
    public String list(HttpServletRequest request, HttpServletResponse response, Model model, MiaoshaUser user) {
        System.out.println(user);
        model.addAttribute("user", user);
        return "goods_list";
    }
}