AutoValue: Moshi Extension

An extension for Google's AutoValue that creates a simple Moshi JsonAdapterFactory for each AutoValue annotated object.

Usage

Simply include auto-value-moshi in your project and annotate your target autovalue class with Moshi's @JsonClass annotation. generateAdapter must be true, and the generator property value should be "avm".

@JsonClass(generateAdapter = true, generator = "avm")
@AutoValue
public abstract class Foo {
  abstract String bar();
  @Json(name="Baz") abstract String baz();

  public static JsonAdapter<Foo> jsonAdapter(Moshi moshi) {
    return new AutoValue_Foo.MoshiJsonAdapter(moshi);
  }
}

Using @JsonClass, no further configuration is necessary. Moshi 1.9+ will automatically pick these types up at runtime.

Legacy alternative

Add a public static method with the following signature to classes you want to get Moshi JsonAdapters. You can also annotate your properties using @Json to define an alternate name for de/serialization.

@AutoValue public abstract class Foo {
  abstract String bar();
  @Json(name="Baz") abstract String baz();

  public static JsonAdapter<Foo> jsonAdapter(Moshi moshi) {
    return new AutoValue_Foo.MoshiJsonAdapter(moshi);
  }
}

Now build your project and de/serialize your Foo.

Generics support

note: this section only applies if using the legacy opt-in via static method. If using @JsonClass, Moshi will handle this automatically.

If the annotated class uses generics, the static method needs a little modification. Simply add a Type[] parameter and pass it to the generated MoshiJsonAdapter class.

@AutoValue public abstract class Foo<T> {
    abstract T data();
    
    public static <T> JsonAdapter<Foo<T>> jsonAdapter(Moshi moshi, Type[] types) {
        return new AutoValue_Foo.MoshiJsonAdapter(moshi, types);
    }
}

Builder Support

If your @AutoValue class has a builder, auto-value-moshi will use the builder to instantiate the class. If the @AutoValue class has a static no-argument factory method for its builder, it will be used. If there are multiple factory methods, the one annotated @AutoValueMoshiBuilder will be used. This can be useful for setting default values.

@JsonClass(generateAdapter = true, generator = "avm")
@AutoValue
public abstract class Foo {
  abstract int bar();
  abstract String quux();

  public static Builder builder() {
    return new AutoValue_Foo.Builder();
  }

  @AutoValueMoshiBuilder
  public static Builder builderWithDefaults() {
    return new builder().quux("QUUX");
  }
}

Factory

note: this section only applies if using the legacy opt-in via static method. If using @JsonClass, Moshi will handle this automatically.

Optionally, auto-value-moshi can create a single JsonAdapter.Factory so that you don't have to add each generated JsonAdapter to your Moshi instance manually.

To generate a JsonAdapter.Factory for all of your auto-value-moshi classes, simply create an abstract class that implements JsonAdapter.Factory and annotate it with @MoshiAdapterFactory, and auto-value-moshi will create an implementation for you. You simply need to provide a static factory method, just like your AutoValue classes, and you can use the generated JsonAdapter.Factory to help Moshi de/serialize your types.

@MoshiAdapterFactory
public abstract class MyAdapterFactory implements JsonAdapter.Factory {

  // Static factory method to access the package
  // private generated implementation
  public static JsonAdapter.Factory create() {
    return new AutoValueMoshi_MyAdapterFactory();
  }
  
}

Then you simply need to register the Factory with Moshi.

Moshi moshi = new Moshi.Builder()
    .add(MyAdapterFactory.create())
    .build();

Transient types

To ignore certain properties from serialization, you can use the @AutoTransient annotation. This comes from a shared transience annotations library and is an api dependency of the runtime artifact. You can annotate a property and it will be treated as transient for both serialization and deserialization. Note that this should only be applied to nullable properties.

Download

Add a Gradle dependency:

annotationProcessor("com.ryanharter.auto.value:auto-value-moshi-extension:1.1.0")
implementation("com.ryanharter.auto.value:auto-value-moshi-runtime:1.1.0")

// If using optional @MoshiAdapterFactory factory
annotationProcessor("com.ryanharter.auto.value:auto-value-moshi-factory:1.1.0")

License

Copyright 2015 Ryan Harter.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.