RAVE

RAVE (Runtime Annotation Validation Engine)

RAVE is a shield that prevents invalid data from crashing or causing hard to spot bugs in your Android apps. RAVE uses java annotation processing to leverage the annotations (Nullness, Value Constraint, Typedef) already present in your model classes to increase safety at runtime. Specifically, it ensures models adhere to the set of expectations that are described by their annotations.

Motivation

Android apps consume data from a variety of sources (network, disk, etc.) that you as an app developer don’t have control over. When external APIs behave badly and return null for something that’s supposed to be @NonNull, your app can crash. Even when APIs behave well, sometimes their corner cases aren’t well-documented, are unknown or may change overtime. RAVE ensures the data you receive from these sources adheres to the set of expectations described by the annotations present on your models.

Application of RAVE

• Validating responses from the network match what the client expects
• Avoiding errors caused by stale schemas when fetching data from disk
• Verifying models are valid after mutation
• Ensuring third party APIs don’t crash your app when providing unexpected data

Installation

Gradle

To integrate RAVE into your project add the following to your 'build.gradle' file:

buildscript {
    repositories {
        maven { url 'https://maven.google.com' }
    }
}

dependencies {
  annotationProcessor 'com.uber:rave-compiler:2.2.0'
  implementation 'com.uber:rave:2.2.0'
}

Proguard Settings

To ensure validators are not removed by Proguard, add the following to your proguard configuration:

-keep class * implements com.uber.rave.ValidatorFactory

If you're using a version of the Android gradle plugin below 2.2 you need to use the apt plugin.

Code Example

Step 1: Create a Factory Class in your module/library.

There can only be one ValidatorFactory in any given module/library. Example:

public final class SampleFactory implements ValidatorFactory {

    @NonNull
    @Override
    public BaseValidator generateValidator() {
        return new SampleFactory_Generated_Validator();
    }
}

In the example above SampleFactory_Generated_Validator is generated once a model references the SampleFactory class using the @Validated annotation. See Step 2.

Step 2: Annotate your models

Example:

@Validated(factory = SampleFactory.class)
public class SimpleModel {

    private String notNullField;
    private String canBeNullField;
    private List<String> names;

    private static final String MATCHED = "Matched";
    private static final String MATCHING = "Matching";
    private static final String NOT_MATCHED = "NotMatched";

    @StringDef({MATCHED, MATCHING, NOT_MATCHED})
    @Retention(RetentionPolicy.SOURCE)
    @interface StringVals { }

    public SimpleModel() {}

    @NonNull
    @StringVals
    public String getNotNullField() {
        return notNullField;
    }

    @Size(5)
    public List<String> getNames() {
        return names;
    }

    @MustBeFalse
    public boolean getIsFalse() {
        return names.size() > 2 && canBeNullField != null;
    }

    @StringVals
    public String getSomeString() {
        return "Matched";
    }
}

Step 3: Start Validating

public void validateMyModel(SimpleModel myModel) {
    try {
        Rave.getInstance().validate(myModel);
    } catch (UnsupportedObjectException e) {
        // handle unsupported error case.
    } catch (RaveException e) {
        // handle rave validation error.
    }
}

Use with Retrofit 2:

Here's a simple recipe to use Rave with Retrofit 2. This is documented and included in the RAVE sample app.

final class RaveConverterFactory extends Converter.Factory {

    static RaveConverterFactory create() {
        return new RaveConverterFactory();
    }

    @Override
    public Converter<ResponseBody, ?> responseBodyConverter(
            Type type, Annotation[] annotations, Retrofit retrofit) {
        Converter<ResponseBody, ?> delegateConverter = retrofit.nextResponseBodyConverter(this, type, annotations);
        return new RaveResponseConverter(delegateConverter);
    }

    private static final class RaveResponseConverter implements Converter<ResponseBody, Object> {

        private final Converter<ResponseBody, ?> delegateConverter;

        RaveResponseConverter(Converter<ResponseBody, ?> delegateConverter) {
            this.delegateConverter = delegateConverter;
        }

        @Override
        public Object convert(ResponseBody value) throws IOException {
            Object convert = delegateConverter.convert(value);
            try {
                Rave.getInstance().validate(convert);
            } catch (RaveException e) {
                // This response didn't pass RAVE validation, throw an exception.
                throw new RuntimeException(e);
            }
            return convert;
        }
    }
}

Advanced Usage

There may be some cases in which you want to exclude/ignore certain models from validation. To do this apply @Excluded to the method that should be exempted from validation. RAVE will not generate validation code for this method.

Supported Annotations

A list of supported annotations can be found here.

Limitations

Rave currently does not validate fields in a model. Rave only validates model methods. If you want a field in a model validated there must be a getter method for that field.

Contributors

We'd love for you to contribute to our open source projects. Before we can accept your contributions, we kindly ask you to sign our Uber Contributor License Agreement.

• If you find a bug, open an issue or submit a fix via a pull request.
• If you have a feature request, open an issue or submit an implementation via a pull request.
• If you want to contribute, submit a pull request.

License

RAVE is released under the Apache License, Version 2.0. See the LICENSE file for more information.