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Overview

exificient-for-json is an implementation of the EXI4JSON specification (see https://www.w3.org/TR/exi-for-json/) in Java. EXI4JSON converts JSON to event streams which result in a very processing efficient and compact format. Lossless round-trip conversion back to the original JSON structures is supported. EXI4JSON is based on EXI and uses its built-in datatypes.

The project uses MIT license.

Background

Due to its EXI/XML nature EXI4JSON can be serialized/visualized as XML. Most of the use-case do not need this features but in some situation it may turn out very hand.

A JSON example

{
  "keyNumber": 123,
  "keyArrayStrings": [
    "s1",
    "s2"
  ]
}

can be transformed to

<j:map xmlns:j="http://www.w3.org/2015/EXI/json">
  <j:keyNumber>
    <j:number>123</j:number>
  </j:keyNumber>
  <j:keyArrayStrings>
    <j:array>
      <j:string>s1</j:string>
      <j:string>s2</j:string>
    </j:array>
  </j:keyArrayStrings>
</j:map>

How to get it

Released with Maven

<dependency>
    <groupId>com.siemens.ct.exi</groupId>
    <artifactId>exificient-for-json</artifactId>
    <version>1.0.0</version>
</dependency>

or also as snapshot.

<dependency>
    <groupId>com.siemens.ct.exi</groupId>
    <artifactId>exificient-for-json</artifactId>
    <version>1.0.1-SNAPSHOT</version>
</dependency>

How to use the library

Java API for JSON Processing

// generate by simply providing input and output
EXIforJSONGenerator e4jGenerator = new EXIforJSONGenerator();
e4jGenerator.generate(isJSON, osEXI4JSON);
// Note: one can also fire events like writeStartObject(),  writeKeyName(key) etc

// parse by simply providing input and output again
EXIforJSONParser e4jParser = new EXIforJSONParser();
e4jParser.parse(isEXI4JSON, osJSON);
// Note: one can again read events by readNextEvent(), getKeyName(),  getValueString() etc

Jackson

EXI4JSONFactory fEXI = new EXI4JSONFactory();
ObjectMapper mapperEXI = new ObjectMapper(fEXI);
ObjectMapper mapperJSON = new ObjectMapper();

String carJson =
    "{ \"brand\" : \"Mercedes\", \"doors\" : 5 }";
JsonNode car = mapperJSON.readTree(carJson); 

// generate
OutputStream e4jOS = ...; // output stream
mapperEXI.writeTree(fEXI.createGenerator(e4jOS), car);
// parse
OutputStream e4jIS = ...; // input stream
EXI4JSONParser eparser = fEXI.createParser(e4jIS);
JsonNode carAgain = mapperJSON.readTree(eparser);

Compression Results

See test-data in https://github.com/EXIficient/exificient-for-json/tree/master/src/test/resources.

On average "EXI4JSON" is about 48% of the original JSON filesize! On average "EXI4JSON" is about 50% smaller than the CBOR binary encoded file!