Overview

This is a Gradle plugin to allow easily performing Java code generation for Apache Avro. It supports JSON schema declaration files, JSON protocol declaration files, and Avro IDL files.

Compatibility

• Java 6 or higher required
• Currently built against Gradle 3.3
  • Currently tested against Gradle 2.0-2.14.1 and 3.0-3.3; other versions may be compatible, but 1.x versions are unlikely to work
• Currently built against Avro 1.8.1
  • Currently tested against Avro 1.8.0-1.8.1; other versions may be compatible
  • If you need support for Avro 1.7.x, try plugin version 0.8.0; versions of Avro before that are unlikely to work

Usage

Add the following to your build.gradle file. Substitute the desired version based on CHANGES.md.

// Gradle 2.1 and later
plugins {
    id "com.commercehub.gradle.plugin.avro" version "VERSION"
}

// Earlier versions of Gradle
buildscript {
    repositories {
        maven {
            url "https://plugins.gradle.org/m2/"
        }
    }
    dependencies {
        classpath "com.commercehub.gradle.plugin:gradle-avro-plugin:VERSION"
    }
}
apply plugin: "com.commercehub.gradle.plugin.avro"

Additionally, ensure that you have a compile dependency on Avro, such as:

repositories {
    jcenter()
}
dependencies {
    compile "org.apache.avro:avro:1.8.1"
}

If you now run gradle build, Java classes will be compiled from Avro files in src/main/avro. Actually, it will attempt to process an "avro" directory in every SourceSet (main, test, etc.)

Configuration

There are a number of configuration options supported in the avro block.

option	default	description
createSetters	true	createSetters passed to Avro compiler
fieldVisibility	"PUBLIC_DEPRECATED"	fieldVisibility passed to Avro compiler
outputCharacterEncoding	see below	outputCharacterEncoding passed to Avro compiler
stringType	"String"	stringType passed to Avro compiler
templateDirectory	see below	templateDir passed to Avro compiler

createSetters

Valid values: true (default), false; supports equivalent String values

Set to false to not create setter methods in the generated classes.

Example:

avro {
    createSetters = false
}

fieldVisibility

Valid values: any FieldVisibility or equivalent String name (matched case-insensitively); default "PUBLIC_DEPRECATED" (default)

By default, the fields in generated Java files will have public visibility and be annotated with @Deprecated. Set to "PRIVATE" to restrict visibility of the fields, or "PUBLIC" to remove the @Deprecated annotations.

Example:

avro {
    fieldVisibility = "PRIVATE"
}

outputCharacterEncoding

Valid values: any Charset or equivalent String name

Controls the character encoding of generated Java files. If the associated JavaCompile task has a configured encoding, it will be used automatically. Otherwise, it will use the value configured in the avro block, defaulting to "UTF-8".

Examples:

// Option 1: configure compilation task (avro plugin will automatically match)
tasks.withType(JavaCompile) {
    options.encoding = 'UTF-8'
}
// Option 2: just configure avro plugin
avro {
    outputCharacterEncoding = "UTF-8"
}

stringType

Valid values: any StringType or equivalent String name (matched case-insensitively); default "String" (default)

By default, the generated Java files will use java.lang.String to represent string types. Alternatively, you can set it to "Utf8" to use org.apache.avro.util.Utf8 or "charSequence" to use java.lang.CharSequence.

avro {
    stringType = "CharSequence"
}

templateDirectory

By default, files will be generated using Avro's default templates. If desired, you can override the template set used by either setting this property or the "org.apache.avro.specific.templates" System property.

avro {
    templateDirectory = "/path/to/velocity/templates"
}

IntelliJ Integration

The plugin attempts to make IntelliJ play more smoothly with generated sources when using Gradle-generated project files. However, there are still some rough edges. It will work best if you first run gradle build, and after that run gradle idea. If you do it in the other order, IntelliJ may not properly exclude some directories within your build directory.

Alternate Usage

If the defaults used by the plugin don't work for you, you can still use the tasks by themselves. In this case, use the com.commercehub.gradle.plugin.avro-base plugin instead, and create tasks of type GenerateAvroJavaTask and/or GenerateAvroProtocolTask.

Here's a short example of what this might look like:

apply plugin: "java"
apply plugin: "com.commercehub.gradle.plugin.avro-base"

dependencies {
    compile "org.apache.avro:avro:1.8.1"
}

task generateAvro(type: com.commercehub.gradle.plugin.avro.GenerateAvroJavaTask) {
    source("src/avro")
    outputDir = file("dest/avro")
}

compileJava.source(generateAvro.outputs)

File Processing

When using this plugin, it is recommended to define each record/enum/fixed type in its own file rather than using inline type definitions. This approach allows defining any type of schema structure, and eliminates the potential for conflicting definitions of a type between multiple files. The plugin will automatically recognize the dependency and compile the files in the correct order. For example, instead of Cat.avsc:

{
    "name": "Cat",
    "namespace": "example",
    "type": "record",
    "fields" : [
        {
            "name": "breed",
            "type": {
                "name": "Breed",
                "type": "enum",
                "symbols" : [
                    "ABYSSINIAN", "AMERICAN_SHORTHAIR", "BIRMAN", "MAINE_COON", "ORIENTAL", "PERSIAN", "RAGDOLL", "SIAMESE", "SPHYNX"
                ]
            }
        }
    ]
}

use Breed.avsc:

{
    "name": "Breed",
    "namespace": "example",
    "type": "enum",
    "symbols" : ["ABYSSINIAN", "AMERICAN_SHORTHAIR", "BIRMAN", "MAINE_COON", "ORIENTAL", "PERSIAN", "RAGDOLL", "SIAMESE", "SPHYNX"]
}

and Cat.avsc:

{
    "name": "Cat",
    "namespace": "example",
    "type": "record",
    "fields" : [
        {"name": "breed", "type": "Breed"}
    ]
}

There may be cases where the schema files contain inline type definitions and it is undesirable to modify them. In this case, the plugin will automatically recognize any duplicate type definitions and check if they match. If any conflicts are identified, it will cause a build failure.