本来想加一个Jackson的配置类修改ObjectMapper实现把null转空字符串或空数组，但是加上之后发现没效果，找不到问题在哪里，不知道是不是我使用@RestControllerAdvice全局返回处理类的问题，所以就自己写了一个工具类方法处理，就在全局返回处理类里面调用
找到配置不生效的问题在哪里了，见springboot中添加Jackson配置类不生效
全局返回处理类是用kotlin写的，用来封装统一响应实体和处理全局异常的，用java也是一样的，语法换成java就行。当然，这不是这篇的博文重点，重点是处理null的方法
package com.gt.gxjhpt.configurationimport cn.dev33.satoken.exception.NotLoginExceptionimport cn.dev33.satoken.exception.NotPermissionExceptionimport cn.dev33.satoken.exception.NotRoleExceptionimport cn.hutool.json.JSONUtilimport com.gt.gxjhpt.entity.RestfulRespimport com.gt.gxjhpt.enumeration.RespCodeEnumimport com.gt.gxjhpt.exception.MyExceptionimport com.gt.gxjhpt.utils.MyUtilsimport org.springframework.core.MethodParameterimport org.springframework.http.HttpStatusimport org.springframework.http.MediaTypeimport org.springframework.http.converter.HttpMessageConverterimport org.springframework.http.server.ServerHttpRequestimport org.springframework.http.server.ServerHttpResponseimport org.springframework.http.server.ServletServerHttpResponseimport org.springframework.validation.BindExceptionimport org.springframework.web.bind.MethodArgumentNotValidExceptionimport org.springframework.web.bind.annotation.ExceptionHandlerimport org.springframework.web.bind.annotation.ResponseStatusimport org.springframework.web.bind.annotation.RestControllerAdviceimport org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdviceimport javax.validation.ConstraintViolationException@RestControllerAdviceclass GlobalResponseBodyAdvice : ResponseBodyAdvice<Any> {override fun supports(returnType: MethodParameter, converterType: Class<out HttpMessageConverter<*>>): Boolean {return true}override fun beforeBodyWrite(body: Any?,returnType: MethodParameter,selectedContentType: MediaType,selectedConverterType: Class<out HttpMessageConverter<*>>,request: ServerHttpRequest,response: ServerHttpResponse): Any? {return when (body) {is RestfulResp<*> -> bodyis String -> JSONUtil.toJsonStr(RestfulResp<Any>().success(body))null -> RestfulResp<Any>().success()else -> {val httpResponse = response as ServletServerHttpResponseif (httpResponse.servletResponse.status.equals(200)) {// 设置null值为空字符串或空数组MyUtils.setNullValue(body)return RestfulResp<Any>().success(body)} else {return body}}}}//其他参数异常@ResponseStatus(HttpStatus.BAD_REQUEST)@ExceptionHandler(value = [BindException::class])fun handleBindException(): RestfulResp<*>? {return RestfulResp<Any>().enumResp(RespCodeEnum.PARAM_ERR)}//parameter异常//为了安全，就不将报错信息返回到前端，只返回粗略信息@ResponseStatus(HttpStatus.BAD_REQUEST)@ExceptionHandler(value = [ConstraintViolationException::class])fun handleValidationException(): RestfulResp<*>? {return RestfulResp<Any>().enumResp(RespCodeEnum.PARAM_ERR)}//bean异常//为了安全，就不将报错信息返回到前端，只返回粗略信息@ResponseStatus(HttpStatus.BAD_REQUEST)@ExceptionHandler(value = [MethodArgumentNotValidException::class])fun handleMethodArgumentNotValidException(ex: MethodArgumentNotValidException?): RestfulResp<*>? {return RestfulResp<Any>().enumResp(RespCodeEnum.PARAM_ERR)}//我的自定义异常@ResponseStatus(HttpStatus.BAD_REQUEST)@ExceptionHandler(MyException::class)fun myException(e: MyException): RestfulResp<*>? {e.printStackTrace()return if (e.msg != null) {RestfulResp<Any>().error(e.msg, e.code)} else if (e.respCodeEnum != null) {RestfulResp<Any>().enumResp(e.respCodeEnum)} else {RestfulResp<Any>().unknown()}}//运行时异常@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)@ExceptionHandler(RuntimeException::class)fun runtimeException(e: RuntimeException): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown(e.message)}//空指针异常@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)@ExceptionHandler(NullPointerException::class)fun nullPointerException(e: NullPointerException): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown("空指针-->>" + e.stackTrace[0].toString())}//未知异常@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)@ExceptionHandler(Exception::class)fun exception(e: Exception): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown(e.message)}// 未提供token@ResponseStatus(HttpStatus.UNAUTHORIZED)@ExceptionHandler(value = [NotLoginException::class])fun exception(e: NotLoginException): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown(e.message)}// 无角色@ResponseStatus(HttpStatus.FORBIDDEN)@ExceptionHandler(NotRoleException::class)fun exception(e: NotRoleException): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown(e.message)}// 无权限@ResponseStatus(HttpStatus.FORBIDDEN)@ExceptionHandler(NotPermissionException::class)fun exception(e: NotPermissionException): RestfulResp<*>? {e.printStackTrace()return RestfulResp<Any>().unknown(e.message)}}
处理null的方法，不需要继续递归的类型，要写在第一个else if条件里面，工具类使用hutool
public static void setNullValue(Object body) throws IllegalAccessException, InstantiationException {Class<?> aClass = body.getClass();if (Collection.class.isAssignableFrom(aClass)) {for (Object it : Convert.toList(body)) {MyUtils.setNullValue(it);}} else if (String.class.isAssignableFrom(aClass) || NumberUtil.isNumber(body.toString())|| BooleanUtil.isBoolean(aClass) || CharUtil.isChar(body) || Date.class.isAssignableFrom(aClass)) {} else if (Map.class.isAssignableFrom(aClass)) {Map<String, Object> objectMap = Convert.toMap(String.class, Object.class, body);objectMap.forEach((k, v) -> {try {if (v == null) {v = "";} else {MyUtils.setNullValue(v);}} catch (IllegalAccessException | InstantiationException e) {e.printStackTrace();}objectMap.put(k, v);});} else { // 自定义响应对象List<Field> fields = CollUtil.toList(aClass.getDeclaredFields());// 父类属性Class<?> superclass = aClass.getSuperclass();while (superclass != null && superclass != Object.class) {fields.addAll(CollUtil.toList(superclass.getDeclaredFields()));superclass = superclass.getSuperclass();}for (Field field : fields) {// 取消权限检查field.setAccessible(true);Object value = field.get(body);if (value == null) {if (Collection.class.isAssignableFrom(field.getType())) {field.set(body, new ArrayList<>());} else if (String.class.isAssignableFrom(field.getType())) {field.set(body, "");}} else {MyUtils.setNullValue(value);}}}}
