vavr-jackson

Jackson datatype module for Vavr library.

This module enables Jackson to seamlessly serialize and deserialize Vavr's functional data types, including immutable collections, tuples, and control types like Option and Either.

Usage

• Jackson 2.x with Vavr 0.x → use vavr-jackson 0.x
• Jackson 3.x with Vavr 0.x → use vavr-jackson 1.x

Maven

<dependency>
  <groupId>io.vavr</groupId>
  <artifactId>vavr-jackson</artifactId>
  <version>1.0.0</version>
</dependency>

Gradle

compile("io.vavr:vavr-jackson:1.0.0")

Registering the Module

Register the VavrModule with your Jackson ObjectMapper:

ObjectMapper mapper = JsonMapper.builder()
    .addModule(new VavrModule())
    .build();

Basic Usage

import io.vavr.collection.List;
import io.vavr.jackson.datatype.VavrModule;
import tools.jackson.core.type.TypeReference;
import tools.jackson.databind.ObjectMapper;
import tools.jackson.databind.json.JsonMapper;

ObjectMapper mapper = JsonMapper.builder()
  .addModule(new VavrModule())
  .build();

String json = mapper.writeValueAsString(List.of(1, 2, 3)); // Result: [1,2,3]
List<Integer> restored = mapper.readValue(json, new TypeReference<>() {}); // Result: List(1, 2, 3)

Supported Types

The module provides serialization and deserialization support for:

Collections

• Sequences: List, Array, Vector, Stream, Queue, IndexedSeq
• Sets: HashSet, LinkedHashSet, TreeSet, Set
• Maps: HashMap, LinkedHashMap, TreeMap, Map
• Multimaps: All Vavr Multimap implementations
• Other: PriorityQueue, CharSeq

Control Types

• Option - Optional values that can be Some or None
• Either - Values that can be Left or Right
• Lazy - Lazily evaluated values

Tuples

• Tuple0 through Tuple8 - Immutable tuples with 0 to 8 elements

Functions

• Function0 through Function8
• CheckedFunction0 through CheckedFunction8

Configuration

You can customize the module behavior using VavrModule.Settings:

Plain Option Format

By default, Option values are serialized in a plain format (just the value or null). You can change this behavior:

VavrModule.Settings settings = new VavrModule.Settings();
ObjectMapper mapper = JsonMapper.builder()
    .addModule(new VavrModule(settings))
    .build();

mapper.writeValueAsString(Option.of(42));  // Result: 42
mapper.writeValueAsString(Option.none());  // Result: null

VavrModule.Settings settings = new VavrModule.Settings().useOptionInPlainFormat(false);
ObjectMapper mapper = JsonMapper.builder()
    .addModule(new VavrModule(settings))
    .build();

mapper.writeValueAsString(Option.of(42));  // Result: ["defined",42]
mapper.writeValueAsString(Option.none());  // Result: ["undefined"]

Deserialize Null as Empty Collection

Configure whether null values should be deserialized as empty collections:

VavrModule.Settings settings = new VavrModule.Settings()
    .deserializeNullAsEmptyCollection(true);
ObjectMapper mapper = JsonMapper.builder()
    .addModule(new VavrModule(settings))
    .build();

List<Integer> result = mapper.readValue("null", new TypeReference<>() {});
// Result: List() (empty list instead of null)