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背景：项目中有些接口的入参需要用户id信息，最简单的做法在每个Controller方法调用的时候获取登录信息然后给入参设置用户id，但是这样就会有很多重复性的工作。另一个可行的也更好的方案可以使用HandlerMethodArgumentResolver来实现。

部分示例代码如下：

1、需要用户id的入参基类

@Data
@ToString
public class WarehouseBaseReq implements Serializable {private String userId;
}

2、新增自定义的解析器处理接口入参设置用户id

@Slf4j
@Component
public class LycMethodArgumentResolver implements HandlerMethodArgumentResolver, InitializingBean {@Autowiredprivate RequestMappingHandlerAdapter adapter;private HandlerMethodArgumentResolver delegate;@Overridepublic void afterPropertiesSet() throws Exception {List<HandlerMethodArgumentResolver> argumentResolvers = adapter.getArgumentResolvers();List<HandlerMethodArgumentResolver> resolverList = new ArrayList<>(argumentResolvers);// 用自定义的resolver代理decorateResolvers(resolverList);adapter.setArgumentResolvers(resolverList);}@Overridepublic boolean supportsParameter(MethodParameter methodParameter) {return delegate.supportsParameter(methodParameter);}@Overridepublic Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {Object obj = delegate.resolveArgument(methodParameter,mavContainer,webRequest,binderFactory);// 判断只有当入参是指定类型才设置if (obj instanceof WarehouseBaseReq) {WarehouseBaseReq requestObj = (WarehouseBaseReq)obj;// 从ThreadLocal中获取登录用户信息UserDto userDto = UserThreadLocal.getUser();if (null != userDto) {// 给接口入参设置用户idrequestObj.setUserId(userDto.getId());}}return obj;}private void decorateResolvers(List<HandlerMethodArgumentResolver> resolverList){for (int i=0; i<resolverList.size();i++){HandlerMethodArgumentResolver resolver = resolverList.get(i);if (resolver instanceof RequestResponseBodyMethodProcessor){this.delegate = resolver;resolverList.set(i,this);break;}}}
}

3、模拟查询仓库的入参

@Data
@ToString(callSuper = true)
public class WarehouseDto extends WarehouseBaseReq {private Long warehouseId;private String warehouseName;private String warehouseCode;
}

4、模拟查询仓库的controller方法

@RestController
@RequestMapping("/web/warehouse")
public class WarehouseController {@Autowiredprivate WarehouseBizService warehouseBizService;@RequestMapping("/testById")public BizRsp<WarehouseDto> testQueryById(@RequestBody WarehouseDto warehouseDto) {log.info("testQueryById方法执行,warehouseDto：{}",warehouseDto);LearingAssert.notNull(warehouseDto.getUserId(),"用户id不能为空");return BizRspUtil.success(warehouseBizService.queryById(warehouseDto));}
}

5、postman中模拟调用接口，入参只需要传递其他参数，结构如下：

{
“warehouseId”:1
}

自此调用方无需传递用户id，controller的方法也无需写重复代码设置用户id即可实现统一添加接口入参参数的效果。
在spring中还有其他一些处理器，可在一些场景下帮助我们更好的实现一些功能。

参考博客：
[1] spring中的各种处理器
[2]方法参数解析器