important! I have to change the project name to ajson
Hello, everyone, I wrote a json parsing library, can quickly and easily get the value, I hope you can try.
project github
Inspiration comes from gjson in golang
Installation
Add it to your Cargo.toml file:
[dependencies]
ajson = "0.1"
Then add it to your code:
extern crate ajson;
A simple example
AJSON get json value with specified path, such as project.name or project.version. When the path matches, it returns immediately!
let data = r#"
{
"project": {
"name": "ajson",
"maintainer": "importcjj",
"version": 0.1,
"rusts": ["stable", "nightly"]
}
}
"#;
let name = ajson::get(data, "project.name");
println!("{}", name.as_str()); // ajson
Syntax
JSON example
{
"name": {"first": "Tom", "last": "Anderson"},
"age":37,
"children": ["Sara","Alex","Jack"],
"fav.movie": "Deer Hunter",
"friends": [
{"first": "Dale", "last": "Murphy", "age": 44, "nets": ["ig", "fb", "tw"]},
{"first": "Roger", "last": "Craig", "age": 68, "nets": ["fb", "tw"]},
{"first": "Jane", "last": "Murphy", "age": 47, "nets": ["ig", "tw"]}
]
}
basic
Below is a quick overview of the path syntax, for more complete information please check out GJSON Syntax.
A path is a series of keys separated by a dot. A key may contain special wildcard characters '*' and '?'. To access an array value use the index as the key. To get the number of elements in an array or to access a child path, use the '#' character. The dot and wildcard characters can be escaped with ''.
name.last >> "Anderson"
age >> 37
children >> ["Sara","Alex","Jack"]
children.# >> 3
children.1 >> "Alex"
child*.2 >> "Jack"
c?ildren.0 >> "Sara"
fav\.movie >> "Deer Hunter"
friends.#.first >> ["Dale","Roger","Jane"]
friends.1.last >> "Craig"
Escape character
Special purpose characters, such as ., *, and ? can be escaped with .
fav\.movie "Deer Hunter"
Arrays
The # character allows for digging into JSON Arrays.To get the length of an array you'll just use the # all by itself.
friends.# 3
friends.#.age [44,68,47]
queries
You can also query an array for the first match by using #(...), or find all matches with #(...)#. Queries support the ==, !=, <, <=, >, >= comparison operators and the simple pattern matching % (like) and !% (not like) operators.
friends.#(last=="Murphy").first >> "Dale"
friends.#(last=="Murphy")#.first >> ["Dale","Jane"]
friends.#(age>45)#.last >> ["Craig","Murphy"]
friends.#(first%"D*").last >> "Murphy"
friends.#(nets.#(=="fb"))#.first >> ["Dale","Roger"]
construct
Basically, you can use selectors to assemble whatever you want, and of course, the result is still a json 
{name.first,age,"murphys":friends.#(last="Murphy")#.first}
[name.first,age,children.0]
ajson::get(json, "name.[first,last]").as_array();
ajson::get(json, "name.first");
ajson::get(json, "name.last");
io::Read
Not only string, AJSON also can parse JSON from io::Read.
use std::fs::File;
let f = file::Open("path/to/json").unwrap();
let json = ajson::parse_from_read(f);
let value = json.get("a.b");
println!("{}", value.as_str());
Value
Value types.
enum Value {
String(String),
Number(Number),
Object(String),
Array(String),
Boolean(bool),
Null,
NotExist,
}
Value has a number of methods that meet your different needs.
value.as_str() -> &str
value.as_u64() -> u64
value.as_i64() -> i64
value.as_f64() -> f64
value.as_bool() -> bool
value.as_array() -> Vec<Value>
value.as_map() -> HashMap<String, Value>
value.get(&str) -> Value
value.exsits() -> bool
value.is_number() -> bool
value.is_string() -> bool
value.is_bool() -> bool
value.is_object() -> bool
value.is_array() -> bool
value.is_null() -> bool
Sometimes you need to check if value exists, you can use exsits(). Notice that when used for null values, exsits returns true.
let v = ajson::get(json, "path");
if v.exsits() {
println!("got it {}", value);
}
get or parse?
Parse needs to read a complete json element, but get returns the result immediately, so get is recommended if you want to simply get a value
Validate
AJSON can help you get the desired value from flawed JSON, but it's worth being more careful because of its looseness.
be careful!!!
Maybe need a validate function 
Performance
$ cargo bench
- ajson
*[serde_json - rust-json
ajson benchmark time: [6.7000 us 6.8023 us 6.9081 us]
change: [-1.8368% -0.4152% +1.0466%] (p = 0.58 > 0.05)
No change in performance detected.
Found 3 outliers among 100 measurements (3.00%)
3 (3.00%) high mild
serde_json benchmark time: [48.196 us 48.543 us 48.947 us]
change: [+2.9073% +4.4909% +6.3532%] (p = 0.00 < 0.05)
Performance has regressed.
Found 3 outliers among 100 measurements (3.00%)
1 (1.00%) high mild
2 (2.00%) high severe
json-rust benchmark time: [24.540 us 24.773 us 25.061 us]
change: [+4.8288% +6.0452% +7.4633%] (p = 0.00 < 0.05)
Performance has regressed.
Found 5 outliers among 100 measurements (5.00%)
4 (4.00%) high mild
1 (1.00%) high severe
- MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports)
- 2.7 GHz Intel Core i7
- 16 GB 2133 MHz LPDDR3
problems
AJSON has just been finished, there may be some bugs and shortcomings, please feel free to issue. Also, Rust is a new language for me, and maybe ajson isn't rust enough, so I hope you have some suggestions.
License
MIT License.
