A Java implementation of the Ion data notation.

This repository contains a git submodule called ion-tests, which holds test data used by ion-java's unit tests.

The easiest way to clone the ion-java repository and initialize its ion-tests submodule is to run the following command.

$ git clone --recursive https://github.com/amazon-ion/ion-java.git ion-java

Alternatively, the submodule may be initialized independently from the clone by running the following commands.

$ git submodule init
$ git submodule update

The submodule points to the tip of the branch of the ion-tests repository specified in ion-java's .gitmodules file.

ion-java may now be built and installed into the local Maven repository with the following command.

$ ./gradlew publishToMavenLocal

To pull upstream changes into ion-java, start with a simple git pull. This will pull in any changes to ion-java itself (including any changes to its .gitmodules file), but not any changes to the ion-tests submodule. To make sure the submodule is up-to-date, use the following command.

$ git submodule update --remote

This will fetch and update the ion-tests submodule from the ion-tests branch currently specified in the .gitmodules file.

For detailed walkthroughs of git submodule usage, see the Git Tools documentation.

To start using ion-java in your code, refer to ion-java on Maven Central to find snippets for adding a dependency on the latest version of the library using your favorite build tool.

Originally ion-java was published using the group id software.amazon.ion. Since 1.4.0 the official groupId was changed to com.amazon.ion to be consistent with other Amazon open source libraries. We still maintain the legacy group id but strongly encourage users to migrate to the official one.

A great way to get started is to use the Ion cookbook. The API documentation will give a lot of detailed information about how to use the library.

If you are looking for an in-memory Ion data model, this library provides IonValue, but you should consider using IonElement from ion-element-kotlin instead.

IonElement is a better choice than IonValue as long as you can work within its limitations. IonElement has significantly less memory overhead than IonValue. It is immutable and does not have references to parent values, so it is always threadsafe, and unlike IonValue there is no need to make deep copies of IonElement. The limitations of IonElement are that it does not support symbols with unknown text, it will bring a dependency on the Kotlin Stdlib, and you may need to change some logic in your application if it relies on being able to access the parent container of an Ion value.

The Ion maintainers recommend using IonElement instead of IonValue whenever possible. For more information, see "Why is IonElement needed?"