protovalidate-java

Protovalidate provides standard annotations to validate common constraints on messages and fields, as well as the ability to use CEL to write custom constraints. It's the next generation of protoc-gen-validate, the only widely used validation library for Protobuf.

With Protovalidate, you can annotate your Protobuf messages with both standard and custom validation rules:

syntax = "proto3";

package banking.v1;

import "buf/validate/validate.proto";

message MoneyTransfer {
  string to_account_id = 1 [
    // Standard rule: `to_account_id` must be a UUID
    (buf.validate.field).string.uuid = true
  ];

  string from_account_id = 2 [
    // Standard rule: `from_account_id` must be a UUID
    (buf.validate.field).string.uuid = true
  ];

  // Custom rule: `to_account_id` and `from_account_id` can't be the same.
  option (buf.validate.message).cel = {
    id: "to_account_id.not.from_account_id"
    message: "to_account_id and from_account_id should not be the same value"
    expression: "this.to_account_id != this.from_account_id"
  };
}

Once you've added protovalidate-java to your project, validation is idiomatic Java:

ValidationResult result = validator.validate(message);
if (!result.isSuccess()) {
    // Handle failure.
}

Installation

Tip

The easiest way to get started with Protovalidate for RPC APIs are the quickstarts in Buf's documentation. There's one available for Java and gRPC.

protovalidate-java is listed in Maven Central, which provides installation snippets for Gradle, Maven, and other package managers. In Gradle, it's:

dependencies {
    implementation 'build.buf:protovalidate:<version>'
}

Documentation

Comprehensive documentation for Protovalidate is available in Buf's documentation library.

Highlights for Java developers include:

• The developer quickstart
• A comprehensive RPC quickstart for Java and gRPC
• A migration guide for protoc-gen-validate users

Additional Languages and Repositories

Protovalidate isn't just for Java! You might be interested in sibling repositories for other languages:

• protovalidate-go (Go)
• protovalidate-python (Python)
• protovalidate-cc (C++)
• protovalidate-es (TypeScript and JavaScript, coming soon!)

Additionally, protovalidate's core repository provides:

• Protovalidate's Protobuf API
• Conformance testing utilities for acceptance testing of protovalidate implementations

Contribution

We genuinely appreciate any help! If you'd like to contribute, check out these resources:

• Contributing Guidelines: Guidelines to make your contribution process straightforward and meaningful
• Conformance testing utilities: Utilities providing acceptance testing of protovalidate implementations

Related Sites

• Buf: Enterprise-grade Kafka and gRPC for the modern age
• Common Expression Language (CEL): The open-source technology at the core of Protovalidate

Legal

Offered under the Apache 2 license.