9 releases

0.1.8 May 25, 2023
0.1.7 May 19, 2023

#45 in Email


899 lines


A very simple and easy-to-use JSON generation tool that supports customizable formats and can be extended with custom Placeholders.


use mock_json::mock;
use serde_json::json;

let val = mock(&json!({
    "msg":"just text",
        "title": "@Title",
            "phones":["@Phone", 1, 3],
    }, 5, 20]

The above code will return a serde_json::Value, and after calling val.to_string(), its content will be as follows:

  "code": 0,
  "msg": "just text",
  "data": [
      "author": {
        "avatar": "https://dummyimage.com/80X80/f7f7f7/fff",
        "blog": "https://fvopl.ktuh.int/dcvr",
        "email": "vpar@hslsl.org",
        "id": "ceE68058-5EaB-4bc2-cCc8-F4a2Dff1Fe6A",
        "id_number": "646734191701136174",
        "ip": "",
        "name": "Patricia Garcia",
        "phones": [
      "datetime": "1960-02-12 03:49:48",
      "id": "3217A3bAAa",
      "title": "bymebox wpvvpv udp pcb lky onigkew sywtnhq"

Generating a List of Data

To generate a list of data, you can use the format [serde_json::Value, min, max], which generates a number of data greater than min and less than max.

 let val = mock(&json!([{"user_name": "@Name", "email": "@Email", "age":"@Number|18~100"}, 2, 5]));

then calling val.to_string(), its content will be:

        "age": 43,
        "email": "dbjfm@drgmz.com",
        "user_name":"Laura White"
        "age": 35,
        "email": "fbac@yefq.edu",
        "user_name":"Frank Hernandez"
        "age": 31,
        "email": "kkhbo@vbqv.cn",
        "user_name":"Jose Wilson"


The principle is to replace the placeholders with the corresponding content. Each placeholder starts with @, followed by a placeholder name, and optional parameters separated by |. For example, @Id will generate a string of length 12 containing [a-zA-Z0-9]. If you want to generate an id of length 5, just use @Id|5. The return value of each placeholder is serde_json::Value.


The default placeholders provided are as follows:


Randomly generates a string in the format of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, without any parameters.

mock(&json!("@Guid")); // String("753c33fE-fFdB-12aF-bC44-A9DD2D7E10aA")


Randomly generates a string of length 12 containing [a-zA-Z0-9]. If you want to generate an id of a custom length, use @Id|5 as an example.

// Default length: 12
mock($json!("@Id")); // String("YNyxSBVzgpQd")

// Custom length
mock(&json!("@Id|5")); // String("vygCt")


Randomly generates a Chinese ID number, no accept params.

mock(&json!("@IdNumber")); // String("665471198804049116")


Randomly generates a Chinese phone number, no accept params.

mock(&json!("@Phone")); // String("13983370699")
mock(&json!("@Phone|86")); // String("+86 13545607699")


Randomly generates a boolean value, no accept params.

mock(&json!("@Bool")); // Bool(true)


Randomly generates an English name. It can accept parameters. If you want to generate a Chinese name, you can pass the parameter cn.

mock(&json!("@Name")); // String("Donald Davis")

// Generate a Chinese name
mock(&jsonQ("@Name|cn")); // String("蔡茗泽")


Randomly generates a first name. It can accept parameters. If you want to generate a Chinese first name, you can pass the parameter cn.

mock(&json!("@FirstName")); // String("Mark")

// Generate a Chinese surname
mock(&json!("@FirstName|cn")); // String("张")


Randomly generates a last name. It can accept parameters. If you want to generate a Chinese last name, you can pass the parameter cn.

mock(&json!("@LastName")); // String("Martin")

// Generate a Chinese last name
mock(&json!("@LastName|cn")); // String("沐宸")


Randomly generates a URL. The protocol of the URL can be customized.

mock(&json!("@Url")); // String("https://mqezx.rpmy.int/gevc")

// Customize the URL protocol
mock(&json!("@Url|ftp")); // String("ftp://qjwb.wpukq.gov/tmkwq")


Randomly generates a token

mock(&json!("@Token")); // String("htK5pesIqPTJYK8Yn286.RG0mgC0vHPlQU7SnxWx3.fHsemPcj43bEY0hJSSfJ")


Randomly generates an email address, no accept params.

mock(&json!("@Email")); // String("hhci@engu.cn")


Randomly generates an IP address. By default, the IP format is IPv4, but it also supports generating IPv6 addresses by passing in ipV6.

// ipv4
mock(&json!("@Ip")); // String("")

// ipv6
mock(&json!("@Ip|ipV6")); // String("D991:53F9:2131:D6CA:86DA:56C4:156D:91B0")


Randomly generates a domain name, no accept params.

mock(&json!("@Domain")); // String("hxca.gov")


Randomly generates a paragraph. To generate a Chinese paragraph, pass in cn.

mock(&json!("@Paragraph")); // String("eetcttp jekaveq uwzkl abzciz bquijz biq ajfbnsjx ljmy khx,..., iilxxy mudlb xjz eipnm wnuc, takktis dus vwmubs ysckswn bju uffje.")

// Chinese paragraph
mock(&json!("@Paragraph|cn")); // String("却国华资称被素火用几花放西等,...,层间者场当族表眼日技里度,际感高一声新历院器火常问书则如。")


Randomly generates a sentence, To generate a Chinese sentence, pass in cn

mock(&json!("@Sentence")); //String("zcdh yiui qymurgx szaydjv yfb tkj znpeyy muzwrs okihyo")

// Chinese sentence
mock(&json!("@Sentence|cn")) // String("型有件次一通说存克这半确毛由")


Randomly generates a title. To generate a Chinese title, pass in cn. It is similar to @Sentence.

mock(&json!("@Title")); // String("fivms iiqq kdvyojq mibvzkx efhi six zpogksf")

// Chinese title
mock(&json!("@Title|cn")); // String("别话省报回京老住基")


Generates a URL for an image provided by https://dummyimage.com. The size, background color, and foreground color can be specified, but it is not possible to define only the background or foreground color.

// Default image size is 320X240, with black background and white foreground
mock(&json!("@Image"));  // String("https://dummyimage.com/320X240/000/fff")

// Custom image size
mock(&json!("@Image|40X40")); // String("https://dummyimage.com/40X40/000/fff")

// Custom size and background color
mock(&json!("@Image|40X40|f00")); // String("https://dummyimage.com/40X40/f00/fff")

// Custom size, background color, and foreground color
mock(&json!("@Image|40X40|f00|fea")); // String("https://dummyimage.com/40X40/f00/fea")


Randomly generates a natural number between 0 and 1000 by default. Accepts parameters to specify a range using @Number|min~max.

mock(&json!("@Number")); // Number(326)

mock(&json!("@Number|100~999")); //Number(437)

mock(&json!("@Number|-200~-100")); // Number(-147)


Randomly generates a floating-point number. Accepts two optional parameters. When there is only one parameter, if the parameter contains ~, it represents the range of values, otherwise, it represents the exact number of decimal places. When there are two parameters, the first parameter represents the exact number of decimal places, and the second parameter represents the range of values.

// default precision is 2
mock(&json!("@Float")); // Number(0.13)

// Specify precision
mock(&json!("@Float|3")); // Number(0.628)

// Specify value range
mock(&json!("@Float|100~999")); // Number(123.56)

// Specify precision and value range
mock(&json!("@Float|2|100~999")); // Number(131.99)


Randomly generates a postal code.

mock(&json!("@Zip")); // String("859615")


Randomly generates an address. Pass in cn to generate a Chinese address.

mock(&json!("@Address")); //String("2454 Kidd Avenue Anchorage Alaska")

// Generate a Chinese address
mock(&json!("@Address|cn")); //String("湖北省武汉市汉阳区仙山社区")


Randomly generates a date. The format can be customized.

mock(&json!("@Date")); //String("1984-09-28")

// Custom date format
mock(&json!("@Date|YYYY/MM/DD")); //String("1918/01/13")

mock(&json!("@Date|YY/M/D")); //String("36/2/1")


Randomly generates a time.

mock(&json!("@Time")); //String("09:58:54")


Randomly generates a date and time. The format can be customized.

mock(&json!("@DateTime")); //String("1937-06-24 10:47:53")

// Custom format
mock(&json!("@DateTime|YYYY/MM/DD hh:mm:ss")); //String("2007/01/23 16:52:03")


Randomly generates a timestamp.

mock(&json!("@Timestamp")); //Number(1812982294012)


Randomly generates a color in hex format.

mock(&json!("@Color")); //String("#F4F54B")


Randomly generates a color in RGB format.

mock(&json!("@RGB")); //String("rgb(79,134,9)")


Randomly generates a color in RGBA format.

mock(&json!("@RGBA")); //String("rgba(240,131,198,0.65)")


Randomly generates a color in HSL format.

mock(&json!("@HSL")); //String("hsl(343,50,32)")

Register your placeholders

The above are all the placeholders currently available. You can also register your own placeholders through the registry function, it must implements the MockFn trait. However, you cannot register placeholders that already exist. Although there is no strict naming convention for placeholders, it is still recommended to use camel case. Except for abbreviations like RGB.

For example: Now I want to register a placeholder called @CMYK, which is used to generate color in cmyk format.

pub struct MockCMYKFn;
impl MockFn for MockCMYKFn {
    // Ignore the parameter since it is not used here.
    fn mock(&self, _:Option<Vec<&str>>) -> Value {
        let mut rng = rand::thread_rng();
        let c = rng.gen_range(0..=100);
        let m = rng.gen_range(0..=100);
        let y = rng.gen_range(0..=100);
        let k = rng.gen_range(0..=100);
        json!(format!("cmyk({},{},{},{})", c, m, y, k))

// Register
registry("@CMYK", MockCMYKFn);

// Usage
mock(&json!("@CMYK")); // String("cmyk(99,20,87,54)))


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