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);

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);