Golang error: 'unexpected end of JSON input' How to solve it?

In recent years, the go language (also known as golang) developed and launched by Google has become one of the choices of many developers. Golang is widely used for its fast compilation speed, efficient memory management and powerful network programming capabilities. But during development, we may encounter various problems. For example, when using the JSON parsing library, we may encounter the error "unexpected end of JSON input".

What is the "unexpected end of JSON input" error?

This error will be triggered when the end of the text is encountered while parsing the JSON text and the entire JSON text cannot be parsed correctly.

Use the encoding/json package to parse JSON in the go language. When we convert JSON into a struct object or map object, we can use the json.Unmarshal method to parse it.

For example, we have such an HTTP response message:

HTTP/1.1 200 OK
Content-Type: application/json

{"code": 200, "message": "success", "data": {"name": "John", "age": 18}}

In order to convert this JSON string into a struct object, we can do this:

type Response struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
    Data    struct {
        Name string `json:"name"`
        Age  int    `json:"age"`
    } `json:"data"`
}

...

resp, err := http.Get(url)
if err != nil {
    // handle error
}
defer resp.Body.Close()

var result Response
decoder := json.NewDecoder(resp.Body)
err = decoder.Decode(&result)
if err != nil {
    // handle error
}

In the above In the example, we obtain the HTTP response from the URL through http.Get and convert the JSON format in the response body into a Response struct object. When the JSON format is incorrect, the "unexpected end of JSON input" error will be triggered.

how to solve this problem?

When processing JSON format, we need to pay attention to some details, such as the correctness of JSON format. When parsing JSON text, you may find that the JSON format is incorrect, such as missing commas, missing quotes, or missing parentheses, etc. If we use the json.Unmarshal method, we must ensure that the JSON format is correct, otherwise we will encounter the "unexpected end of JSON input" error.

In the sample code, we parse the response body in JSON format into a Response structure through decoder.Decode(&result). However, if the response body format is incorrect, "unexpected end of JSON input" will be triggered. "mistake.

In order to solve this problem, we should verify the JSON format of the response body. We can use some tools, such as JSONLint, to verify the JSON format. If the JSON is well-formed, it can be parsed successfully. If the JSON format is incorrect, you need to fix the JSON format to correctly parse the response body.

In actual encoding, we can use the following approach to verify the JSON format:

resp, err := http.Get(url)
if err != nil {
    // handle error
}
defer resp.Body.Close()

result := make(map[string]interface{})
decoder := json.NewDecoder(resp.Body)
decoder.UseNumber() // 避免JSON数字溢出
err = decoder.Decode(&result)
if err != nil {
    // handle error
}

In the above example, we first created an empty map object. Then we obtain a decoder object through the json.NewDecoder method and parse the response body using the decoder.Decode method. We also call the decoder.UseNumber method to avoid JSON number overflow.

We need to handle errors when the JSON format is incorrect. We can handle errors using the following code:

respBody, err := ioutil.ReadAll(resp.Body)
if err != nil {
    // handle error
}

if err := json.Unmarshal(respBody, &result); err != nil {
    fmt.Println("JSON parse error:", err)
    return err
}

In the above example, we first read the response body and parsed the JSON text using the json.Unmarshal method. If the JSON format is incorrect, an error message is returned.

Through the above method, we can avoid the occurrence of "unexpected end of JSON input" errors and ensure that our code can correctly parse the JSON format. In actual development, we should also pay attention to the correctness and legality of the JSON format to ensure that our code can process data accurately and efficiently.

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