在 Spring Controller 中返回原始类型/包装器的最佳方法是什么？

Question

When I return Integer or other wrapper from my Spring Controller like that:

@GetMapping(path = "test1")
public Integer test1() {
    return 1;
}

The response to the user has the following body:

1

It's not a valid JSON. Are there any practices on how such values should be returned? The concern is that I want my all API to return a valid JSON. I created a wrapper that returns:

{
    "value": 1
}

But, maybe there is a better way to tackle these cases?

Answer 1

If the return value is returned as plain text, eg a String is returned without double-quotes, then the following would be true:

• You use @RestController or @ResponseBody

• Your code doesn't specify a response content type

• The client prefers text response over JSON response

To force the response to JSON, you need to tell Spring by specifying:

@GetMapping(path = "test1", produces = "application/json")

or

@GetMapping(path = "test1", produces = MediaType.APPLICATION_JSON_VALUE)

---

Since your response is just a number, you could decide that it is just that, and not JSON, by specifying eg text/plain as the response content type. As with any other response, it is up to the client to correctly interpret the response value.

However, the plain 1-byte response 1 is valid JSON, so you can keep that, or you can do the { "value": 1 } JSON response if you want. It is your API, so you get to decide what the response format is.

Just remember to document it, so whoever writes client code will know what to expect.