之前遇到jdk版本升级，新版本的JDK对一些反射相关的功能进行了限制从而引发的问题，我自己遇到的是在上传excel文件失败，开始以为是文件上传方式的问题，检测无误后还是没解决。

1.下面是controller

@PostMapping(value = "/importExcel", consumes = "multipart/*", headers = "content-type=multipart/form-data")
    @ResponseBody
    public void importExcel(@RequestPart(value = "file") MultipartFile file) throws Exception {

consumes = "multipart/*" 加不加这个也没啥用。
@RequestParam或者@RequestPart都可以

2.网络请求-标头

请求 URL: http://localhost:8080/api/merchantscarrier/importExcel
请求方法: POST
状态代码: 415 
远程地址: [::1]:8080
引用站点策略: strict-origin-when-cross-origin
Accept: multipart/form-data, multipart/*
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: http://localhost:8000
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Connection: keep-alive
Content-Encoding: gzip
Content-Type: application/json
Date: Fri, 17 Jun 2022 09:06:21 GMT
Expires: 0
Keep-Alive: timeout=60
Pragma: no-cache
Transfer-Encoding: chunked
Vary: origin,access-control-request-method,access-control-request-headers,accept-encoding
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 1; mode=block
Accept: application/json
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9
Authorization: Bearer eyJhbGciOiJIUzIXXX
Connection: keep-alive
Content-Length: 2
Content-Type: application/json;charset=UTF-8
Host: localhost:8080
Origin: http://localhost:8000
Referer: http://localhost:8000/
sec-ch-ua: " Not A;Brand";v="99", "Chromium";v="102", "Microsoft Edge";v="102"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-site
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.5005.124 Safari/537.36 Edg/102.0.1245.41

3.响应的错误信息

2022-06-17 17:05:44 WARN  o.s.w.s.m.s.DefaultHandlerExceptionResolver - Resolved [org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json;charset=UTF-8' not supported]

从网页测试根本行不通，我用apipostman测试，文件可以过来但是报新的错误

Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @6a400542

4.解决

这是由于 JDK 8 中有关反射相关的功能自从 JDK 9 开始就已经被限制了，为了兼容原先的版本，需要在运行项目时添加 --add-opens java.base/java.lang=ALL-UNNAMED 选项来开启这种默认不被允许的行为。

--add-opens java.base/java.lang=ALL-UNNAMED

除了添加选项启动选项之外，由于原本的项目是在 JDK 8 的环境中运行的，此时需要将运行的 JDK 转变为 JDK 11，具体做法（仅针对 Maven 项目）：将父 pom.xml 文件中的 <java.version> 标签中的 java 版本修改为需要运行的版本，具体如下所示：

<properties>
    <java.version>17</java.version>
</properties>