golang-显示字符，不显示ascii。 类似于“＆”，而不是“ \ 0026”

This is my testing code.Just make a simple http server. Then generating a json data that it's value is "&". But the result is what i don't want. The result is below the code block.

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"
)

func testFunc(w http.ResponseWriter, r *http.Request) {
    data := make(map[string]string)
    data["key"] = "&"
    bytes, err := json.Marshal(data)
    if err != nil {
        fmt.Fprintln(w, "generator json error")
    } else {
        //print console
        fmt.Println(string(bytes))
        fmt.Println("&")
        //print broswer
        fmt.Fprintln(w, string(bytes))
        fmt.Fprintln(w, "&")
    }
}

func main() {
    http.HandleFunc("/", testFunc)
    err := http.ListenAndServe(":9090", nil)
    if err != nil {
        log.Fatal("ListenAndServe", err)
    }

}

result: Chrome browser show:

{"key":"\u0026"}

&

Console also show:

{"key":"\u0026"}

&

When '&' not in json, browser and console will print '&'.

From the docs (emphasis by me):

String values encode as JSON strings. InvalidUTF8Error will be returned if an invalid UTF-8 sequence is encountered. The angle brackets "<" and ">" are escaped to "\u003c" and "\u003e" to keep some browsers from misinterpreting JSON output as HTML. Ampersand "&" is also escaped to "\u0026" for the same reason.

Apparently if you want to send '&' as is, you'll need to either create a custom Marshaler, or use RawMessage type like this: http://play.golang.org/p/HKP0eLogQX.

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
)

type Search struct {
    Query string `json:"query"`
}

func main() {
    data := &Search{Query: "http://google.com/?q=stackoverflow&ie=UTF-8"}
    responseJSON, _ := JSONMarshal(data, true)
    fmt.Println(string(responseJSON))

}

func JSONMarshal(v interface{}, safeEncoding bool) ([]byte, error) {
    b, err := json.Marshal(v)

    if safeEncoding {
        b = bytes.Replace(b, []byte("\\u003c"), []byte("<"), -1)
        b = bytes.Replace(b, []byte("\\u003e"), []byte(">"), -1)
        b = bytes.Replace(b, []byte("\\u0026"), []byte("&"), -1)
    }
    return b, err
}

Results:

JSONMarshal(data, true)
{"query":"http://google.com/?q=stackoverflow&ie=UTF-8"}

JSONMarshal(data, false)
{"query":"http://google.com/?q=stackoverflow\u0026ie=UTF-8"}

Credits: https://github.com/clbanning/mxj/blob/master/json.go#L20

Playbook: http://play.golang.org/p/c7M32gICl8

In Go1.7 they have added a new option to fix this:

encoding/json: add Encoder.DisableHTMLEscaping This provides a way to disable the escaping of <, >, and & in JSON strings.

The relevant function is

func (*Encoder) SetEscapeHTML

That should be applied to a Encoder.

enc := json.NewEncoder(os.Stdout)
enc.SetEscapeHTML(false)

The example of stupidbodo modified: https://play.golang.org/p/HnWGJAjqPA

Another way to solve the problem is to simply replace those escaped characters in json.RawMessage into just valid UTF-8 characters, after the json.Marshal() call.

You can use the strconv.Quote() and strconv.Unquote() to do so.

func _UnescapeUnicodeCharactersInJSON(_jsonRaw json.RawMessage) (json.RawMessage, error) {
    str, err := strconv.Unquote(strings.Replace(strconv.Quote(string(_jsonRaw)), `\\u`, `\u`, -1))
    if err != nil {
        return nil, err
    }
    return []byte(str), nil
}

func main() {
    // Both are valid JSON.
    var jsonRawEscaped json.RawMessage   // json raw with escaped unicode chars
    var jsonRawUnescaped json.RawMessage // json raw with unescaped unicode chars

    // '\u263a' == '☺'
    jsonRawEscaped = []byte(`{"HelloWorld": "\uC548\uB155, \uC138\uC0C1(\u4E16\u4E0A). \u263a"}`) // "\\u263a"
    jsonRawUnescaped, _ = _UnescapeUnicodeCharactersInJSON(jsonRawEscaped)                        // "☺"

    fmt.Println(string(jsonRawEscaped))   // {"HelloWorld": "\uC548\uB155, \uC138\uC0C1(\u4E16\u4E0A). \u263a"}
    fmt.Println(string(jsonRawUnescaped)) // {"HelloWorld": "안녕, 세상(世上). ☺"}
}

https://play.golang.org/p/pUsrzrrcDG-

Hope this helps.