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protovalidate-java

protovalidate-java is the Java language implementation of protovalidate designed to validate Protobuf messages at runtime based on user-defined validation constraints. Powered by Google's Common Expression Language (CEL), it provides a flexible and efficient foundation for defining and evaluating custom validation rules. The primary goal of protovalidate is to help developers ensure data consistency and integrity across the network without requiring generated code.

The protovalidate project

Head over to the core protovalidate repository for:

• The API definition: used to describe validation constraints
• Documentation: how to apply protovalidate effectively
• Migration tooling: incrementally migrate from protoc-gen-validate
• Conformance testing utilities: for acceptance testing of protovalidate implementations

Other protovalidate runtime implementations include:

• C++: protovalidate-cc
• Go: protovalidate-go
• Python: protovalidate-python

And others coming soon:

• TypeScript: protovalidate-ts

Installation

To include protovalidate-java in your project, add the following to your build file:

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

Remember to always check for the latest version of protovalidate-java on the project's GitHub releases page to ensure you're using the most up-to-date version.

Usage

Implementing validation constraints

Validation constraints are defined directly within .proto files. Documentation for adding constraints can be found in the protovalidate project README and its comprehensive docs.

syntax = "proto3";

package my.package;

import "google/protobuf/timestamp.proto";
import "buf/validate/validate.proto";

message Transaction {
  uint64 id = 1 [(buf.validate.field).uint64.gt = 999];
  google.protobuf.Timestamp purchase_date = 2;
  google.protobuf.Timestamp delivery_date = 3;
  
  string price = 4 [(buf.validate.field).cel = {
    id: "transaction.price",
    message: "price must be positive and include a valid currency symbol ($ or £)",
    expression: "(this.startsWith('$') || this.startsWith('£')) && double(this.substring(1)) > 0"
  }];
  
  option (buf.validate.message).cel = {
    id: "transaction.delivery_date",
    message: "delivery date must be after purchase date",
    expression: "this.delivery_date > this.purchase_date"
  };
}

Example

In your Java code, create an instance of the Validator class and use the validate method to validate your messages.

// Import the required packages
package build.buf;

import build.buf.protovalidate.results.ValidationException;
import build.buf.protovalidate.results.ValidationResult;
import com.my.package.Transaction;
import com.google.protobuf.Timestamp;

import build.buf.protovalidate.Validator;
import build.buf.protovalidate.Config;

public class Main {

    // Create timestamps for purchase and delivery date
    Timestamp purchaseDate = Timestamp.newBuilder().build();
    Timestamp deliveryDate = Timestamp.newBuilder().build();

    // Create a transaction object using the Builder pattern
    Transaction transaction =
            Transaction.newBuilder()
                    .setId(1234)
                    .setPrice("$5.67")
                    .setPurchaseDate(purchaseDate)
                    .setDeliveryDate(deliveryDate)
                    .build();

    // Create a validator object with the default Configuration
    Validator validator = new Validator();
    // Validate the transaction object using the validator
    try {
        ValidationResult result = validator.validate(transaction);

        // Check if there are any validation violations
        if (result.getViolations().isEmpty()) {
            // No violations, validation successful
            System.out.println("Validation succeeded");
        } else {
            // Print the violations if any found
            System.out.println(result.toString());
        }
    } catch (ValidationException e) {
        // Catch and print any ValidationExceptions thrown during the validation process
        System.out.println("Validation failed: " + e.getMessage());
    }
}

Ecosystem

• protovalidate core repository
• Buf
• CEL Spec

Legal

Offered under the Apache 2 license.