ig-json-parser

Fast JSON parser for java projects

Getting started

The easiest way to get started is to look at maven-example. For more comprehensive examples, check out the unit tests or the demo.

Maven

To use this library, add this to your build.gradle file:

ext {
  generatedSourcesDir = file("gen-src/main/java")
}

repositories {
  mavenCentral()
}

sourceSets {
  main {
    java {
      srcDir 'src/main/java'
    }
  }
}

dependencies {
  compile group: 'com.instagram', name: 'ig-json-parser-processor', version: '0.0.6+'
}

Requirements for model classes

There should be a package-visible no-argument constructor for each of your model classes. The fields also need to be package-visible.

Each class that needs a serializer/deserializer generated should be annotated with @JsonType. Each field that needs to be mapped to/from JSON should be annotated with @JsonField. The @JsonField annotation has one mandatory argument, which is the fieldname for the field in the JSON.

The following is an example of a very simple model class:

@JsonType
class Dessert {
  @JsonField(fieldName="type")
  String type;

  @JsonField(fieldName="rating")
  float rating;
}

Serializer/deserializer

Compiling your model classes with the annotations will automatically generate the serializer and deserializer. They will be in a generated class with the same name as your class, except with the suffix __JsonHelper. For example, to deserialize the Dessert class above, simply run the code:

Dessert parsed = Dessert__JsonHelper.parseFromJson(inputJsonString);

To serialize a class, run:

String serialized = Dessert__JsonHelper.serializeToJson(dessertObject);

Supported data types

The following scalar types are supported:

• String
• boolean/Boolean
• int/Integer
• long/Long
• float/Float
• double/Double

If a json field is another dictionary, it can be represented by another model class. That model class must also have the @JsonType annotation.

Lists of objects are supported either as Java Lists or Queues.

Proguard

Add the following lines to your proguard-rules file:

-dontwarn sun.misc.Unsafe
-dontwarn javax.annotation.**

Advanced features

Postprocessing

TODO: Document this. See the documentation in common/src/main/java/com/instagram/common/json/annotation/JsonType.java in the meanwhile.

Customized parsing code

TODO: Document this. See the documentation in common/src/main/java/com/instagram/common/json/annotation/JsonField.java in the meanwhile.

Optional serializer generation

To save generating serializer code if you only need deserialization, serializer generation can be disabled or enabled globally and per-class. The default is to generate serializers for all classes. To disable generation globally, pass

-AgenerateSerializer=false

to the command-line arguments of javac. To override the default generation option for a single class, see JsonType.generateSerializer().