Amazon Ion Java

A Java implementation of the Ion data notation.

Setup

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

Pulling in Upstream Changes

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.

Depending on the Library

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.

Legacy group id

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.

Using the Library

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.

Alternatives

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?”