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")

  ...
}