# Jackson

Jackson is a multi-purpose Java library for processing JSON. Jackson aims to be the best possible combination of fast, correct, lightweight, and ergonomic for developers.

Jackson features:

Multi processing mode, and very good collaboration

Not only annotations, but also mixed annotations

Fully support generic types

Support polymorphic types

# Full Data Binding Example

JSON data

  "name" : { "first" : "Joe", "last" : "Sixpack" },
  "gender" : "MALE",
  "verified" : false,
  "userImage" : "keliuyue"

It takes two lines of Java to turn it into a User instance:

ObjectMapper mapper = new ObjectMapper(); // can reuse, share globally
User user = mapper.readValue(new File("user.json"), User.class);


public class User {

    public enum Gender {MALE, FEMALE};

    public static class Name {
        private String _first, _last;

        public String getFirst() {
            return _first;

        public String getLast() {
            return _last;

        public void setFirst(String s) {
            _first = s;

        public void setLast(String s) {
            _last = s;

    private Gender _gender;
    private Name _name;
    private boolean _isVerified;
    private byte[] _userImage;

    public Name getName() {
        return _name;

    public boolean isVerified() {
        return _isVerified;

    public Gender getGender() {
        return _gender;

    public byte[] getUserImage() {
        return _userImage;

    public void setName(Name n) {
        _name = n;

    public void setVerified(boolean b) {
        _isVerified = b;

    public void setGender(Gender g) {
        _gender = g;

    public void setUserImage(byte[] b) {
        _userImage = b;

Marshalling back to JSON is similarly straightforward:

mapper.writeValue(new File("user-modified.json"), user);