jiangshikun / jackson-utils

Useful utilities when using Jackson for JSON serialization and deserialization

jackson-utils

Utilities for reading and writing JSON and XML using Jackson.

Requirements

• Compatible with Java 8+

Serialization and Deserialization

Enumerated Types

When deserializating strings into Java Enum types, it's useful to be able to accept lowercase, uppercase and mixed-cased string input.

This deserializer attempts to coerce the string value using the provided case first, but then falls back to UPPERCASE or lowercase if needed.

objectMapper.registerModule(new SimpleModule()
        .setDeserializerModifier(new EnumUppercaseDeserializerModifier()));

Trimming Whitespace

When deserializing string values, it's useful to automatically trim leading and trailing whitespace including newlines, tabs, etc.

This deserializer uses the Character.isWhitespace(char) function to determine what is whitespace.

objectMapper.registerModule(new SimpleModule()
        .addDeserializer(String.class, TrimWhitespaceDeserializer.SINGLETON));

ZonedDateTime

When serializing and deserializing ZonedDateTime values, it's useful to accept a wide variety of string formats.

In addition to the widely-supported ISO date format, you also get variety of other common formats:

• yyyy-MM-dd
• yyyyMMdd
• yyyyMMMddd
• MM/dd/yyyy
• MM-dd-yyyy
• MM.dd.yyyy
• dd-MMM-yyyy
• MMM dd, YYYY
• MMMM dd, yyyy

objectMapper.registerModule(new SimpleModule()
        .addSerializer(new ZonedDateTimeSerializer()) //
        .addDeserializer(ZonedDateTime.class, new ZonedDateTimeDeserializer());

GeoPoint

This library exposes an immutable GeoPoint class that represents a lat/lon coordinate. GeoPoint supports a variety of serialization and deserialization options, which happen to be compatible with those used by Elasticsearch.

Latitude and longitude fields

"location": {
  "lat": 41.12,
  "lon": -71.34
}

Comma separated latitude and longitude

"location": "41.12,-71.34"

Geohash

"location": "drm3btev3e86"

MapPath

When deserializing JSON that does not conform to a fixed schema, it's sometimes useful to deserialize the JSON to native Java objects like Map and List instead using Jackson's tree structure (e.g. JsonNode).

When we do this however we lose the ability to traverse the data in an easy way and null-safe manner. Enter MapPath, which is loosely inspired by JsonPath.

Let's assume the following JSON input:

{
  "store": {
    "book": [
      {
        "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
      },
      {
        "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
      },
      {
        "category": "fiction",
        "author": "Herman Melville",
        "title": "Moby Dick",
        "isbn": "0-553-21311-3",
        "price": 8.99
      },
      {
        "category": "fiction",
        "author": "J. R. R. Tolkien",
        "title": "The Lord of the Rings",
        "isbn": "0-395-19395-8",
        "price": 22.99
      }
    ],
    "bicycle": {
      "color": "red",
      "price": 19.95
    }
  },
  "expensive": 10
}

Let's use Jackson to parse this JSON into a Map.

String json = "...see above...";
Map map = objectMapper.readValue(json, Map.class);

Let's wrap the Map using MapPath

MapPath mapPath = MapPath.of(map);

Now we can traverse the properties of the map very easily:

   mapPath.getString("store.bicycle.color")    ' red
   mapPath.getDouble("store.bicycle.price")    ' 19.95
   mapPath.getInt("expensive")                 ' 10

Installation

The library is available on Maven Central.

Maven

Add the following to your pom.xml:

<repositories>
    <repository>
        <id>central</id>
        <name>Central Repository</name>
        <url>http://repo.maven.apache.org/maven2</url>
        <releases>
            <enabled>true</enabled>
        </releases>
    </repository>
</repositories>

...

<dependency>
    <groupId>com.arakelian</groupId>
    <artifactId>jackson-utils</artifactId>
    <version>3.8.0</version>
    <scope>compile</scope>
</dependency>

Gradle

Add the following to your build.gradle:

repositories {
  mavenCentral()
}

dependencies {
  compile 'com.arakelian:jackson-utils:3.8.0'
}

Licence

Apache Version 2.0