JSONLD-JAVA

This is a Java implementation of the JSON-LD specification (http://json-ld.org/).

The code is based off the jsonld.js and PyLD implementations found on the json-ld homepage.

USAGE

In Java

compiling

jsonld-java uses maven to compile

mvn compile

packaging

Either run mvn jar:jar and grab the generated jar file from target/jsonld-java-1.0.0-SNAPSHOT.jar or run mvn install -Dmaven.test.skip=true to install the jar into your local maven repository.

in your project (maven specific)

<dependency>
    <groupId>dfki.km.json</groupId>
    <artifactId>jsonld-java</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</dependency>

Note that the dependencies for the various rdf libraries are marked as optional, and will not be included unless specifically stated in your project's pom (this means that you will get a ClassNotFoundException for anything in the de.dfki.km.jsonld.impl package unless you specifically specify their dependencies in your pom).

E.g. if you wish to use the JenaJSONLDSerializer or the JenaTripleCallback add the following to your project's pom.

<dependency>
    <groupId>com.hp.hpl.jena</groupId>
	<artifactId>jena</artifactId>
    <version>2.6.4</version>
</dependency>

or if you want to use the Sesame libraries:

<dependency>
    <groupId>org.openrdf.sesame</groupId>
	<artifactId>sesame-model</artifactId>
	<version>2.6.4</version>
</dependency>

This also allows you to specify the version or this library you wish to use (however, if you don't use the same version it's not garanteed that the api will be the same which may cause some problems).

running tests

mvn test

Note that these currently fail due to the lack of an implementation of frame.

code example

// Open a valid json(-ld) input file
InputStream inputStream = new FileInputStream("input.json");
// Read the file into an Object (The type of this object will be a List, Map, String, Boolean,
// Number or null depending on the root object in the file).
Object jsonObject = JSONUtils.fromInputStream(inputStream);
// Create a JSONLDProcessor
JSONLDProcessor processor = new JSONLDProcessor();
// Call whichever JSONLD function you want! (e.g. normalize)
Object normalized = processor.normalize(jsonObject);
// Print out the result (or don't, it's your call!)
System.out.println(JSONUtils.toString(normalized));

Adding JSON-LD triples to Jena

// Create a JenaTripleCallback object
JenaTripleCallback callback = new JenaTripleCallback();
// Optionally add your Jena Model to the callback (a default Model will be created if you don't
// run this).
callback.setJenaModel(jenaModel);
// call the triples function of the processor
processor.triples(jsonObject, callback);
// If you didn't use your own Jena Model, get the resulting one with:
Model m = callback.getJenaModel();

Adding JSON-LD triples to Sesame

// Create a SesameTripleCallback object
SesameTripleCallback callback = new SesameTripleCallback();
// Optionally add your Sesame Graph to the callback (a default Graph will be created if you don't
// run this).
callback.setStorageGraph(storageGraph);
// call the triples function of the processor
processor.triples(jsonObject, callback);
// If you didn't use your own Sesame graph, get the resulting one with:
Graph output = callback.getStorageGraph();

Serializing a Jena Model to JSON-LD

// Create an instance of the Jena serializer
JenaJSONLDSerializer serializer = new JenaJSONLDSerializer();
// import the Jena Model
serializer.importModel(model);
// grab the resulting JSON-LD map
Map<String,Object> jsonld = serializer.asObject();

Serializing to JSON-LD from other sources

// Create an instance of the serializer
JSONLDSerializer serializer = new JSONLDSerializer();
// Optionally Add and extra prefix->uri mappinds you want (e.g. the following line)
serializer.setPrefix("http://xmlns.com/foaf/0.1/", "foaf");
// for each triple you have where the object is a literal
// (if datatypeURI is null, a plain literal will be assumed and language may be null or an empty string)
serializer.triple(subjectURI, perdicateURI, value, datatypeURI, language);
// for each triple you have where the object is an URI
serializer.triple(subjectURI, predicateURI, objectURI);
// grab the resulting JSON-LD map
Map<String,Object> jsonld = serializer.asObject();

Non-Specification Extras

Ignore Keywords

The function ignoreKeyword(String) in the JSONLDProcessor allows you to specify any keys that should not be treated as JSON-LD, and thus not processed. Any keys specified to be ignored will still be present in resulting objects, but will be exactly the same as their original. The only exception is triples, which simply skips over the keys as it doesn't make sense to generate triples for objects that aren't RDF.

Simplify

The function simplify(Object) goes over all the keys in the input and attempts to make "SimpleName":"URI" mappings for each key and generates a new context for the input based on these mappings. The resulting output should look like a very basic JSON document except for the @ keys.

RDF2JSONLD

This is a simple function which takes an input file in rdfxml or n3 and outputs it in JSON-LD

initial setup

mvn -quiet clean package
chmod +x ./target/appassembler/bin/rdf2jsonld

usage

./target/appassembler/bin/rdf2jsonld <options> <input>
    input: a filename or URL to the rdf input (in rdfxml or n3)
    options:
            -expand : expand the jsonld output
            -normalize : normalize the jsonld output

NOTES

TODO

• Make sure Jena Implementation is correct (i.e. write some real tests)
• Tests for the serializations
• Implement frame.
• As the code is almost a direct translation from the javascript and python implementation, there is probably a lot of optimization work to do.