请求json的具体布局取决于JAX-RS框架的配置，但默认情况下，它是不带包装的普通JSON对象.在您的情况下，我将发送以下JSON:

The concrete layout of the request json depends on the configuration of the JAX-RS framework, but by default it is a plain JSON object without a wrapper. In your case, I would send this JSON:

{
   "userId": "arun0009", 
   "extension": ".png",    
   "text": null,
   "image": "BASE_64_ENCODED_IMAGE"
}

java端已经知道"期望的对象，因此添加的包装器不是必需的，并且(如您所注意到的)添加无效.

The java side already "knows" what object to expect, so the wrapper you added is not necessary and (as you noticed) not valid to add.