springboot 2.7.6 fastjson 2.0.21 Controller 接收@RequestBody参数 提示非法反射警告

我不确定这个是我配置问题还是bug，所以提了个问题支持；
## pom
``` xml

4.0.0

org.springframework.boot
spring-boot-starter-parent
2.7.6


com.example
demo
0.0.1-SNAPSHOT
demo
demo

11



org.springframework.boot
spring-boot-starter-web



org.springframework.boot
spring-boot-starter-json

com.alibaba.fastjson2
fastjson2
2.0.21


com.alibaba.fastjson2
fastjson2-extension
2.0.21

org.springframework.boot
spring-boot-maven-plugin

```

剔除了jackson依赖 然后配置了FastJsonHttpMessageConverter
``` java
package com.example.demo.config;

import com.alibaba.fastjson2.JSONWriter;
import com.alibaba.fastjson2.support.config.FastJsonConfig;
import com.alibaba.fastjson2.support.spring.http.converter.FastJsonHttpMessageConverter;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

import java.nio.charset.StandardCharsets;
import java.util.Collections;
import java.util.List;

@Configuration
public class BackendWebMvcConfig extends WebMvcConfigurationSupport {

@Override
public void configureMessageConverters(List> converters) {
//定义一个convert转换消息的对象
FastJsonHttpMessageConverter fastConverter=new FastJsonHttpMessageConverter();
//添加fastjson的配置信息，比如是否要格式化返回的json数据；
FastJsonConfig fastJsonConfig = new FastJsonConfig();
fastJsonConfig.setWriterFeatures(
//是否输出值为null的字段,默认为false
JSONWriter.Feature.WriteMapNullValue,
//将Collection类型字段的字段空值输出为[]
JSONWriter.Feature.WriteNullListAsEmpty,
//将字符串类型字段的空值输出为空字符串
JSONWriter.Feature.WriteNullStringAsEmpty
);
//在convert中添加配置信息
fastConverter.setFastJsonConfig(fastJsonConfig);
//设置支持的媒体类型
fastConverter.setSupportedMediaTypes(Collections.singletonList(MediaType.APPLICATION_JSON));
//设置默认字符集
fastConverter.setDefaultCharset(StandardCharsets.UTF_8);
//将convert添加到converters
converters.add(0, fastConverter);

//解决返回字符串带双引号问题
StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
stringHttpMessageConverter.setSupportedMediaTypes(Collections.singletonList(MediaType.TEXT_PLAIN));
stringHttpMessageConverter.setDefaultCharset(StandardCharsets.UTF_8);
converters.add(0, stringHttpMessageConverter);

super.addDefaultHttpMessageConverters(converters);
}
}
```
Controller 代码
``` java
package com.example.demo.user;

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {

@RequestMapping("test")
public String test(){
return "test";
}

@PostMapping("login")
public User login(@RequestBody User user){
System.out.println(user);
return user;
}
}

```

User 代码
``` java
package com.example.demo.user;

public class User {

private String username;
private String password;

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

@Override
public String toString() {
return "User{" +
"username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}

```
调用 login 方法后

警告：
```
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.alibaba.fastjson2.util.JDKUtils (file:/E:/DEV/maven/maven-Repository/com/alibaba/fastjson2/fastjson2/2.0.21/fastjson2-2.0.21.jar) to field java.lang.String.COMPACT_STRINGS
WARNING: Please consider reporting this to the maintainers of com.alibaba.fastjson2.util.JDKUtils
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
```

不确定这个警告后期有没有影响过来问一下 ，有消除这个警告的方法么？

Start with the supplied pom.xml, BackendWebMvcConfig, UserController, and User class, then reproduce the login request on Java 11 with fastjson2 2.0.21. Inspect the warning from com.alibaba.fastjson2.util.JDKUtils regarding java.lang.String.COMPACT_STRINGS and determine whether the warning is expected; done means the cause and any supported way to remove or avoid it are documented or verified.

Written by the indexing model from the issue text.