Data Validation in Rust: validator library

What is validator?

validator is a popular library for data validation in Rust. It provides flexible and expressive tools for checking the correctness of input data: strings, numbers, email addresses, URLs, IP addresses, UUIDs, and much more. The library is based on macros and traits, allowing you to easily combine validation rules and create custom checks.

Why is data validation needed?

In any application that works with user input, APIs, or configuration files, it is critically important to validate data before using it. Validation errors can lead to program crashes, vulnerabilities, or incorrect behavior. The validator library helps to:

Guarantee data integrity
Reduce the amount of boilerplate code
Ensure uniform error handling
Simplify testing

Installation

Add validator to the Cargo.toml file:

[dependencies]validator = "0.18"serde = { version = "1.0", features = ["derive"] }

serde is also often used for deserializing data before validation.

Main Features

Validation attributes — #[validate(...)] for struct fields
Built-in validators: length, range, email, url, ip, uuid, contains, regex, custom
Nested validation — recursive checking of nested structures
Custom validators — via functions or closures
Error grouping — collecting all validation errors into a single ValidationErrors object

Rust Code Example

use validator::Validate;use serde::Deserialize;

#[derive(Debug, Deserialize, Validate)]struct User {    #[validate(length(min = 2, max = 50))]    name: String,

    #[validate(email)]    email: String,

    #[validate(range(min = 13, max = 120))]    age: u8,

    #[validate(url)]    website: Option<String>,}

fn main() {    let user = User {        name: "A".to_string(),        email: "invalid-email".to_string(),        age: 10,        website: Some("not-a-url".to_string()),    };

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