Serde Json 简单使用

2022-12-30 381 words 2 minutes

Contents

Serde Json

添加依赖

cargo add serde --features derive
cargo add serde_json
cargo add serde_derive

结构体的序列化与反序列化

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point {x: 1, y: 2};
    let json: String = serde_json::to_string(&point).unwrap();
    println!("{}", json);

    let point: Point = serde_json::from_str(&json).unwrap();
    println!("{:#?}", point);
}

枚举的序列化与反序列化

第一种枚举类型

参照结构体的序列化和反序列化，如果对一个枚举进行序列化，我们发现

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
enum Week {
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday,
}

fn main() {
    let json: String = serde_json::to_string(&Week::Friday).unwrap();
    println!("{}", json);

    let week: Week = serde_json::from_str(&json).unwrap();
    println!("{:#?}", week);
}

运行结果如下

"Friday"
Friday

这个不是我们想的JSON格式，我们可以添加一个 serde(tag) 宏

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
#[serde(tag = "WeekDay")]
enum Week {
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday,
}

fn main() {
    let json: String = serde_json::to_string(&Week::Friday).unwrap();
    println!("{}", json);

    let week: Week = serde_json::from_str(&json).unwrap();
    println!("{:#?}", week);
}

运行结果如下

{
    "WeekDay": "Friday"
}

Friday

哟系，结果不错

第二种枚举类型

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
enum IP {
    IPv4(String),
    IPv6(String)
}

fn main() {
    let json: String = serde_json::to_string(&IP::IPv4("127.0.0.1".to_string())).unwrap();
    println!("{}", json);

    let ip: IP = serde_json::from_str(&json).unwrap();
    println!("{:#?}", ip);
}

运行结果如下

{
    "IPv4": "110.26.73.83"
}
IPv4(
    "110.26.73.83",
)

我们可以添加一些操作，让其结构变的更合理一些

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
#[serde(tag = "type", content = "ip")]
enum IP {
    IPv4(String),
    IPv6(String)
}

fn main() {
    let json: String = serde_json::to_string(&IP::IPv4("127.0.0.1".to_string())).unwrap();
    println!("{}", json);

    let ip: IP = serde_json::from_str(&json).unwrap();
    println!("{:#?}", ip);
}

运行结果如下

{
    "type": "IPv6",
    "ip": "::ffff:110.26.73.83"
}
IPv6(
    "::ffff:110.26.73.83",
)

Unit Struct 的序列化与反序列化

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
struct UnitStruct;

fn main() {
    let json: String = serde_json::to_string(&UnitStruct).unwrap();
    println!("{}", json);

    let n: UnitStruct = serde_json::from_str(&json).unwrap();
    println!("{:#?}", n);
}

运行结果如下

null
UnitStruct

一些选项

忽略某个字段

#[serde(skip_serialize)] 在序列化时忽略该字段
#[serde(skip_deserialize)] 在反序列化时忽略该字段
#[serde(skip)] 同时忽略这个字段

可是这样以后，结构体在反序列化时会造成运行时错误

#[macro_use]
extern crate serde_derive;

use serde::{Serialize, Deserialize};

#[derive(Debug, Serialize, Deserialize)]
struct Point {
    x: f64,
    #[serde(skip_serializing)]
    y: f64
}

fn main() {
    let point = Point {
	x: 1.0,
	y: 2.0
    };

    let json: String = serde_json::to_string(&point).unwrap(); // this is ok
    println!("{}", json);

    let point: Point = serde_json::from_str(&point).unwrap(); // this is not ok
    println("{:#?}", point);
}

提供默认值

在上面的例子中，我们可以通过提供默认值来解决错误

#[derive(Debug, Serialize, Deserialize)]
struct Point {
    x: f64,
    #[serde(skip_serializing, default)]
    y: f64
}

也可以手动设置提供值的函数

#[derive(Debug, Serialize, Deserialize)]
struct Point {
    x: f64,
    #[serde(skip_serializing, default="default_y")]
    y: f64
}

fn default_y() -> f64 {
    5.0
}

重命名字段

#[derive(Debug, Serialize, Deserialize)]
struct Point {
    #[serde(rename = "X")]
    x: f64,
    #[serde(rename = "Y")]
    y: f64,
}