使用post方法时，使用requestBody接收数据时，如何将接收的实体中字段值为空字符串的字段转为null

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使用post方法时且使用requestBody接收数据时，如何将接收的实体中字段值为空字符串的字段值转为null

The issue does not name a source file, test, or entry point; it only asks how POST request-body entities can convert empty-string fields to null. Start by locating the request-body deserialization guidance or examples, then document the supported configuration or usage and verify the behavior with a focused example.

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