1. extern crate serde_json;
    3. use serde_json::{Value, Map, Number};
    5. fn main() {
    6.     let mut inner_map = Map::new();
    7.     inner_map.insert("x".to_string(), Value::Number(Number::from(10u64)));
    8.     inner_map.insert("y".to_string(), Value::Number(Number::from(20u64)));
    10.     let mut map = Map::new();
    11.     map.insert("key1".to_string(), Value::String("test".to_string()));
    12.     map.insert(
    13.         "key2".to_string(),
    14.         Value::Array(vec![
    15.             Value::String("a".to_string()),
    16.             Value::String("b".to_string()),
    17.         ]),
    18.     );
    19.     map.insert("key3".to_string(), Value::Object(inner_map));
    21.     println!("{}", serde_json::to_string(&map).unwrap());
    22.     // => {"key1":"test","key2":["a","b"],"key3":{"x":10,"y":20}}
    23. }