In this post, Alan Zimmer explains how the Azure SDK for Java transitioned from jackson-databind to in-house azure-json and azure-xml libraries, exploring the technical motivations, migration details, and integration points with common serialization frameworks.

Overview

jackson-databind (Jackson) has been a foundation for JSON serialization in the Java ecosystem. However, maintaining reliability in the Azure SDK for Java became challenging due to dependency version conflicts and the Java module system’s stricter requirements. To address these, the Azure SDK for Java team developed and adopted azure-json and azure-xml libraries.

Why Replace jackson-databind?

  • Dependency Conflicts: Different Java libraries pull in unique versions of Jackson, which can lead to runtime issues when dependencies clash.
  • Reflection Issues: Jackson’s heavy reliance on reflection makes it less compatible with the Java module system and can impact security policies.
  • SDK Compatibility: Reducing dependency issues improves the Azure SDK’s flexibility and reliability for diverse Java environments.

Introducing azure-json and azure-xml

To minimize reliance on Jackson, Azure SDK for Java now provides:

Key Features

  • Both libraries support streaming readers and writers.
  • Offer interfaces (JsonSerializable and XmlSerializable) for custom serialization behavior.
  • No runtime dependencies, mitigating further dependency conflicts.

azure-json

  • Includes JsonReader, JsonWriter, and JsonSerializable.
  • Inspired by the JSON specification, jackson-core, and Gson.
  • Uses a JsonProvider SPI, with the default implementation leveraging shaded jackson-core.
  • Offers a model-based JSON structure in com.azure.json.models.

azure-xml

  • Provides XmlReader, XmlWriter, and XmlSerializable.
  • Modeled after Java’s javax.xml.stream streaming APIs.
  • Uses and wraps Java’s XMLStreamReader and XMLStreamWriter.
  • For performance, resorts to shaded aalto-xml if possible.

Result: Reduced dependency on Jackson and reflection, and improved module-system compatibility.

Changes in Azure SDK for Java Model Serialization

  • Before: Models used jackson-annotations.
  • Now: Models implement JsonSerializable and XmlSerializable.

Benefits:

  • Reduces the need for reflection.
  • Eases the support for dual JSON and XML serialization.

Integrating with Jackson and Gson

To facilitate interoperability, the Azure SDK team provides helpers for integrating with Jackson and Gson:

  • Jackson Integration:

    • Use JacksonJsonProvider.getJsonSerializableDatabindModule() to register with Jackson’s ObjectMapper:

      ObjectMapper objectMapper = JsonMapper.builder()
    .addModule(JacksonJsonProvider.getJsonSerializableDatabindModule())
    .build();
  • Gson Integration:

    • Use GsonJsonProvider.getJsonSerializableTypeAdapterFactory() to register with Gson’s GsonBuilder:

      Gson gson = new GsonBuilder()
    .registerTypeAdapterFactory(GsonJsonProvider.getJsonSerializableTypeAdapterFactory())
    .create();

These providers ensure JsonSerializable types in the Azure SDK work seamlessly with these popular serialization frameworks.

Status of Jackson Dependencies

  • Current State:
    • Azure SDK for Java client libraries still depend on jackson-annotations, jackson-core, and jackson-databind within azure-core where streaming APIs or other features can’t yet be replaced.
    • jackson-dataformat-xml has been removed.
    • Most libraries outside of azure-core* removed direct Jackson dependencies, relying on the Azure libraries instead.
  • Future Direction:
    • The team is researching the possibility of completely removing Jackson from azure-core.

Feedback

For questions or concerns, developers are encouraged to contact the Azure SDK for Java team on GitHub.

Post by Alan Zimmer for the Azure SDK Blog.

This post appeared first on “Microsoft DevBlog”. Read the entire article here