rustHow to read JSON file in Rust

Reading a JSON file in Rust is relatively straightforward. First, you need to use the serde_json crate to parse the JSON file. Then, you can use the serde::Deserialize trait to deserialize the JSON data into a Rust struct. Finally, you can use the serde::Serialize trait to serialize the data back into a JSON string. The following ## Code example shows how to read a JSON file and deserialize it into a Rust struct:

use serde::{Deserialize, Serialize};
use serde_json::Result;

#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: u8,
    phones: Vec<String>,
}

fn main() -> Result<()> {
    // Open the file in read-only mode with buffer.
    let file = std::fs::File::open("person.json")?;
    let reader = std::io::BufReader::new(file);

    // Read the JSON contents of the file as an instance of `Person`.
    let p: Person = serde_json::from_reader(reader)?;

    println!("{} is {} years old", p.name, p.age);

    // Convert `Person` back to a JSON string.
    let j = serde_json::to_string(&p)?;

    println!("{}", j);
    Ok(())
}

The output of the above ## Code example would be:

John is 30 years old
{"name":"John","age":30,"phones":["555-1234","555-2345"]}

The serde_json crate provides the serde::Deserialize and serde::Serialize traits which allow you to easily deserialize and serialize JSON data into Rust structs. The serde_json::from_reader function is used to read the JSON file and deserialize it into a Rust struct. The serde_json::to_string function is used to serialize the data back into a JSON string.

Helpful links

• serde_json crate
• serde::Deserialize trait
• serde::Serialize trait

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