serde

Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.

仅依赖syn ,quote ,proc-macro2

基本操作

use serde::{Deserialize, Serialize};
// 主要是 Serialize，Deserialize 这两个宏
#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point { x: 1, y: 2 };

    // Convert the Point to a JSON string.
    let serialized = serde_json::to_string(&point).unwrap();

    // Prints serialized = {"x":1,"y":2}
    println!("serialized = {}", serialized);

    // Convert the JSON string back to a Point.
    let deserialized: Point = serde_json::from_str(&serialized).unwrap();

    // Prints deserialized = Point { x: 1, y: 2 }
    println!("deserialized = {:?}", deserialized);
}

Deserialize

#![allow(unused)]
fn main() {
// 以该结构为例子
#[derive(Serialize,Debug)]
struct Duration{
    secs:usize,
    nanos:usize,
}

// 方便反序列化
impl Duration {
    fn new(secs:usize,nanos:usize) -> Duration{
        return Duration {
            secs:secs,
            nanos:nanos,
        }
    }
}

// 实现反序列化

impl<'de> Deserialize<'de> for Duration {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        enum Field { Secs, Nanos }

        // This part could also be generated independently by:
        //
        //    #[derive(Deserialize)]
        //    #[serde(field_identifier, rename_all = "lowercase")]
        //    enum Field { Secs, Nanos }
        // 给每个字段实现反序列化
        impl<'de> Deserialize<'de> for Field {
            fn deserialize<D>(deserializer: D) -> Result<Field, D::Error>
            where
                D: Deserializer<'de>,
            {

                struct FieldVisitor;
                // visitor用于处理基本类型
                impl<'de> Visitor<'de> for FieldVisitor {
                    type Value = Field;

                    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                        formatter.write_str("`secs` or `nanos`")
                    }

                    fn visit_str<E>(self, value: &str) -> Result<Field, E>
                    where
                        E: de::Error,
                    {
                        match value {
                            "secs" => Ok(Field::Secs),
                            "nanos" => Ok(Field::Nanos),
                            _ => Err(de::Error::unknown_field(value, FIELDS)),
                        }
                    }
                }

                // 处理字段名
                deserializer.deserialize_identifier(FieldVisitor)
            }
        }

        struct DurationVisitor;

        impl<'de> Visitor<'de> for DurationVisitor {
            type Value = Duration;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("struct Duration")
            }
            // 针对序列
            fn visit_seq<V>(self, mut seq: V) -> Result<Duration, V::Error>
            where
                V: SeqAccess<'de>,
            {
                let secs = seq.next_element()?
                    .ok_or_else(|| de::Error::invalid_length(0, &self))?;
                let nanos = seq.next_element()?
                    .ok_or_else(|| de::Error::invalid_length(1, &self))?;
                Ok(Duration::new(secs, nanos))
            }
            // 常见的反序列化map
            fn visit_map<V>(self, mut map: V) -> Result<Duration, V::Error>
            where
                V: MapAccess<'de>,
            {
                let mut secs = None;
                let mut nanos = None;
                while let Some(key) = map.next_key()? {
                    match key {
                        Field::Secs => {
                            if secs.is_some() {
                                return Err(de::Error::duplicate_field("secs"));
                            }
                            secs = Some(map.next_value()?);
                        }
                        Field::Nanos => {
                            if nanos.is_some() {
                                return Err(de::Error::duplicate_field("nanos"));
                            }
                            nanos = Some(map.next_value()?);
                        }
                    }
                }
                let secs = secs.ok_or_else(|| de::Error::missing_field("secs"))?;
                let nanos = nanos.ok_or_else(|| de::Error::missing_field("nanos"))?;
                Ok(Duration::new(secs, nanos))
            }
        }

        const FIELDS: &'static [&'static str] = &["secs", "nanos"];
        deserializer.deserialize_struct("Duration", FIELDS, DurationVisitor)
    }
}

// 最后测试
    let d = Duration{secs:123,nanos:345};
    let ds = serde_json::to_string(&d).unwrap();
    println!("{}",ds);
    let dd:Duration = serde_json::from_str(&ds).unwrap();
    println!("{:#?}",dd);


}