GiG.Core.Messaging.Avro.Schema.Generator.MSBuild.md

GiG.Core.Messaging.Avro.Schema.Generator.MSBuild

This Library provides a Code Generator that generates the Avro schema for Public Events objects.

Schema Generator Basic Usage

This code generation package leverages Roslyn both for code generation and code analysis. It does not load application binaries and as a result avoids issues caused by clashing dependency versions and differing target frameworks.

This packages should be installed into all projects which contain Public.Events. Installing a package injects a target into the project which will generate code at build time.

Usage

• Identify the project containing Public.Events that need to be published to the Avro Schema Registry and Kafka.
• Install package [GiG.Core.Messaging.Avro.Schema.Abstractions]
• Install package [GiG.Core.Messaging.Avro.Schema.Generator.MSBuild]
• Decorate classes with [NamedSchema(doc: "")] and properties with [Field("")]
• Build you project

Example of generated code

Event model, including NamedSchema and Field attributes:

[NamedSchema(doc: "Represents a person")]
public partial class Person
{
	[Field(nameof(Email))]
	public string Email { get; set; }

	[Field(nameof(Id))]
	public Guid Id { get; set; }

	[Field(nameof(Address))]
	public Address Address { get; set; }

	[Field(nameof(Gender), defaultValue: Gender.Unspecified)]
	public Gender Gender { get; set; }

	[Field(nameof(Age), "Person's age", -1)]
	public int? Age { get; set; }

	[Field(nameof(Fullname))]
	public string Fullname { get; set; }

	[Field(nameof(DateOfBirth))]
	public DateTime DateOfBirth { get; set; }
	
	[Field(nameof(Data))]
	public byte[] Data { get; set; }
}

Generated code

public partial class Person : ISpecificRecord
{
	// ReSharper disable once InconsistentNaming
	// ReSharper disable once MemberCanBePrivate.Global
	// ReSharper disable once FieldCanBeMadeReadOnly.Global
	public static Schema _SCHEMA = Schema.Parse(@"{""type"":""record"",""name"":""Person"",""namespace"":""KafkaMessaging.Models"",""doc"":""Represents a person"",""fields"":[{""name"":""Email"",""type"":""string""},{""name"":""Id"",""type"":{""name"":""Id"",""type"":""fixed"",""size"":16}},{""name"":""Address"",""type"":{""type"":""record"",""name"":""Address"",""namespace"":""KafkaMessaging.Models"",""doc"":""Represents an address"",""fields"":[{""name"":""AddressLine1"",""type"":""string""},{""name"":""AddressLine2"",""type"":""string""},{""name"":""City"",""type"":""string""},{""name"":""Country"",""type"":{""name"":""Country"",""type"":""enum"",""symbols"":[""UNSPECIFIED"",""MALTA"",""GOZO"",""COMINO""]},""default"":""UNSPECIFIED""},{""name"":""Region"",""type"":{""type"":""record"",""name"":""Region"",""namespace"":""KafkaMessaging.Models"",""doc"":""Represents a Region"",""fields"":[{""name"":""Name"",""type"":""string""}]}}]}},{""name"":""Gender"",""type"":{""name"":""Gender"",""type"":""enum"",""symbols"":[""UNSPECIFIED"",""MALE"",""FEMALE""]},""default"":""UNSPECIFIED""},{""name"":""Age"",""type"":{""type"":""array"",""items"":""int""}},{""name"":""Fullname"",""type"":""string""},{""name"":""DateOfBirth"",""type"":""long"",""logicalType"":""timestamp-millis""},{""name"":""Data"",""type"":""bytes""}]}");

	public object Get(int fieldPos)
	{
		switch (fieldPos)
		{
			case 0: return Email;
			case 1: return Id.ToString();
			case 2: return Address;
			case 3: return SerializeEnum(Gender);
			case 4: return Age.GetValueOrDefault();
			case 5: return Fullname;
			case 6: return SerializeDateTime(DateOfBirth);
			case 7: return SerializeBytes(Data);

			default: throw new AvroRuntimeException("Bad index " + fieldPos + " in Get()");
		}
	}

	public void Put(int fieldPos, object fieldValue)
	{
		switch (fieldPos)
		{
			case 0: Email = (string)fieldValue; break;
			case 1: Id = Guid.Parse((string)fieldValue); break;
			case 2: Address = (KafkaMessaging.Models.Address)fieldValue; break;
			case 3: Gender = DeserializeEnum<KafkaMessaging.Models.Gender>(fieldValue); break;
			case 4: Age = (int?)fieldValue; break;
			case 5: Fullname = (string)fieldValue; break;
			case 6: DateOfBirth = DeserializeDateTime((long)fieldValue); break;
			case 7: Data = DeserializeBytes((byte[])fieldValue); break;

			default: throw new AvroRuntimeException("Bad index " + fieldPos + " in Put()");
		}
	}

	public Schema Schema => _SCHEMA;
	
	#region DateTime serialization helpers
	
	private static long SerializeDateTime(DateTime timestamp)
	{
		var dateTimeOffset = new DateTimeOffset(timestamp.ToUniversalTime());
		return dateTimeOffset.ToUnixTimeMilliseconds();
	}
	
	private static DateTime DeserializeDateTime(long timestamp)
	{
		var dateTimeOffset = DateTimeOffset.FromUnixTimeMilliseconds(timestamp);
		return dateTimeOffset.UtcDateTime;
	}
	
	#endregion
	
	#region Bytes serialization helpers

	private static readonly byte[] DefaultByteArray = new byte[0];
	
	private static byte[] SerializeBytes(byte[] data)
	{
		return data ?? DefaultByteArray;
	}
	
	private static byte[] DeserializeBytes(byte[] data)
	{
		return data?.Length > 0 ? data : null;
	}
	
	#endregion
	
	#region Enum serialization helpers
	
	private static string SerializeEnum(Enum value)
	{
		return value.ToString().ToUpperInvariant();
	}
	
	private static TModel DeserializeEnum<TModel>(object data)
	{
		var val = Enum.Parse(typeof(TModel), data.ToString());
		return (TModel) val;
	}
	
	#endregion
}