Data Validation in Rust: validator Library

What is data validation in Rust and why is it needed?

Data validation is the process of checking the correctness of input data before processing it. In Rust, a systems programming language focused on safety and performance, validation is especially important as it helps prevent logical errors, data leaks, and program crashes. The validator library provides a declarative approach to checking struct fields using attributes, making the code clean and maintainable.

How to install the validator library?

Add the dependency to the Cargo.toml file:

[dependencies]validator = "0.16"validator_derive = "0.16"

Then run the cargo build command to download and compile the library.

Main features of the library

• Built-in validators: checking string length (min/max), email, URL, numeric ranges, regular expressions, and much more.
• Struct attributes: use #[derive(Validate)] and field annotations, for example #[validate(email)].
• Custom validators: create your own functions for specific rules.
• Error grouping: returns a collection of errors with the field name and message.
• Nested struct support: recursive validation of complex objects.

Rust code example

use validator::Validate;

#[derive(Debug, Validate)]struct User {    #[validate(length(min = 3, max = 20))]    username: String,    #[validate(email)]    email: String,    #[validate(range(min = 18, max = 120))]    age: u8,}

fn main() {    let user = User {        username: String::from("al"),        email: String::from("invalid-email"),        age: 15,    };

    match user.validate() {        Ok(_) => println!("Data is valid"),        Err(errors) => {            for (field, err) in &errors {                println!("Error in field {}: {:?}", field, err);            }        }    }}

In this example, the username length, email format, and age are checked. If they do not match, a list of errors is displayed.

When to use validator?

• When developing a REST API to validate incoming requests.
• In configuration files (YAML, JSON) to ensure settings are correct.
• When working with user input — registration, forms, comments.
• In data parsers where strict control of types and formats is required.
• In systems with high requirements for security and reliability.

The validator library is ideal for projects where Rust's performance and code readability are important. It integrates easily with other crates, such as serde for deserialization.