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<!--
SPDX-FileCopyrightText: © 2021 Matthias Andreas Benkard <code@mail.matthias.benkard.de>
SPDX-License-Identifier: GFDL-1.3-or-later
-->
# GVariant for Java
This library provides a [GVariant][] parser in pure Java.
## Overview
`jgvariant-core` provides `Decoder<T>`, which read a given type of
GVariant-encoded value from a [ByteBuffer][]. The class also contains
factory methods to acquire those instances.
The various subclasses of `Decoder` together implement the [GVariant
serialization][] specification.
`jgvariant-ostree` provides instances of `Decoder<T>` for various
[GVariant][] types used in [OSTree][] repositories.
## Example
To parse a [GVariant][] value of type `"a(si)"`, which is an array of
pairs of [String][] and `int`, you can use the following code:
record ExampleRecord(String s, int i) {}
var decoder =
Decoder.ofArray(
Decoder.ofStructure(
ExampleRecord.class,
Decoder.ofString(StandardCharsets.UTF_8),
Decoder.ofInt().withByteOrder(ByteOrder.LITTLE_ENDIAN)));
byte[] bytes = ...;
List<ExampleRecord> example = decoder.decode(ByteBuffer.wrap(bytes));
## Command line tool
The `jgvariant-tool` module contains a tool called `jgvariant` that can
be used to manipulate [GVariant][]-formatted files from the command line.
Its primary purpose is to enable the scripting of [OSTree][] repository
management tasks.
Usage example (dumping the contents of an [OSTree][] summary file):
$ jgvariant ostree summary read ./jgvariant-ostree/src/test/resources/ostree/summary
You can build the tool either as a shaded JAR or as a native executable.
To build and run a shaded JAR:
$ mvn package -pl jgvariant-tool -am -Pshade
$ java -jar /home/mulk/Arbeitskasten/jgvariant/jgvariant-tool/target/jgvariant-tool-*.jar
To build and run a native executable:
$ mvn package -pl jgvariant-tool -am -Pnative
$ ./jgvariant-tool/target/jgvariant
## Library installation
### Usage with Maven
<project>
...
<dependencyManagement>
...
<dependencies>
<dependency>
<groupId>eu.mulk.jgvariant</groupId>
<artifactId>jgvariant-bom</artifactId>
<version>0.1.7</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
...
</dependencyManagement>
<dependencies>
...
<dependency>
<groupId>eu.mulk.jgvariant</groupId>
<artifactId>jgvariant-core</artifactId>
</dependency>
<dependency>
<groupId>eu.mulk.jgvariant</groupId>
<artifactId>jgvariant-ostree</artifactId>
</dependency>
...
</dependencies>
...
</project>
### Usage with Gradle
dependencies {
...
implementation(platform("eu.mulk.jgvariant:jgvariant-bom:0.1.7")
implementation("eu.mulk.jgvariant:jgvariant-core")
implementation("eu.mulk.jgvariant:jgvariant-ostree")
...
}
[ByteBuffer]: https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/nio/ByteBuffer.html
[GVariant]: https://docs.gtk.org/glib/struct.Variant.html
[GVariant serialization]: https://people.gnome.org/~desrt/gvariant-serialisation.pdf
[OSTree]: https://ostreedev.github.io/ostree/
[String]: https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html
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