Genson: JSON Processing API for Java and Scala

Using @JsonSerialize annotation, you can specify custom serializer for a model class and @JsonDeserialize annotation used to specify custom deserializer.

Step 1: Define serializer by extending JsonSerializer class.

public class AddressSerializer extends JsonSerializer<Address> {

        @Override
        public void serialize(Address address, JsonGenerator gen, SerializerProvider serializers)
                        throws IOException, JsonProcessingException {
                gen.writeStartObject();
                gen.writeStringField("address", getCommmaSeparatedAddress(address));
                gen.writeEndObject();

        }

        private static String getCommmaSeparatedAddress(Address address) {
                StringBuilder builder = new StringBuilder();
                builder.append(address.getStreet()).append(",").append(address.getCity()).append(",")
                                .append(address.getCountry());
                return builder.toString();
        }

}

Step 2: Define deserializer by extending JsonDeserializer class.

public class AddressDeserializer extends JsonDeserializer<Address> {

        @Override
        public Address deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
                TreeNode node = jp.getCodec().readTree(jp);

                String addressStr = node.get("address").toString();

                return getAddress(addressStr);
        }

        private static Address getAddress(String addr) {
                Address address = new Address();

                String[] tokens = addr.split(",");
                address.setStreet(tokens[0]);
                address.setCity(tokens[1]);
                address.setCountry(tokens[2]);

                return address;
        }

}

Step 3: Specify serializer using @JsonSerialize annotation and deserializer using @JsonDeserialize annotation.

@JsonDeserialize(using = AddressDeserializer.class)
@JsonSerialize(using = AddressSerializer.class)
public class Address {
        .....
        .....
}

Find the below working application.

Address.java

package com.sample.app.model;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.sample.app.serializer.AddressDeserializer;
import com.sample.app.serializer.AddressSerializer;

@JsonDeserialize(using = AddressDeserializer.class)
@JsonSerialize(using = AddressSerializer.class)
public class Address {

        private String street;
        private String city;
        private String country;

        public String getStreet() {
                return street;
        }

        public void setStreet(String street) {
                this.street = street;
        }

        public String getCity() {
                return city;
        }

        public void setCity(String city) {
                this.city = city;
        }

        public String getCountry() {
                return country;
        }

        public void setCountry(String country) {
                this.country = country;
        }

        @Override
        public String toString() {
                StringBuilder builder = new StringBuilder();
                builder.append("Address [street=");
                builder.append(street);
                builder.append(", city=");
                builder.append(city);
                builder.append(", country=");
                builder.append(country);
                builder.append("]");
                return builder.toString();
        }

}

Employee.java

package com.sample.app.model;

public class Employee {
        private String firstName;
        private String lastName;
        private Address address;

        public String getFirstName() {
                return firstName;
        }

        public void setFirstName(String firstName) {
                this.firstName = firstName;
        }

        public String getLastName() {
                return lastName;
        }

        public void setLastName(String lastName) {
                this.lastName = lastName;
        }

        public Address getAddress() {
                return address;
        }

        public void setAddress(Address address) {
                this.address = address;
        }

        @Override
        public String toString() {
                StringBuilder builder = new StringBuilder();
                builder.append("Employee [firstName=");
                builder.append(firstName);
                builder.append(", lastName=");
                builder.append(lastName);
                builder.append(", address=");
                builder.append(address);
                builder.append("]");
                return builder.toString();
        }

}

AddressSerializer.java

package com.sample.app.serializer;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.sample.app.model.Address;

public class AddressSerializer extends JsonSerializer<Address> {

        @Override
        public void serialize(Address address, JsonGenerator gen, SerializerProvider serializers)
                        throws IOException, JsonProcessingException {
                gen.writeStartObject();
                gen.writeStringField("address", getCommmaSeparatedAddress(address));
                gen.writeEndObject();

        }

        private static String getCommmaSeparatedAddress(Address address) {
                StringBuilder builder = new StringBuilder();
                builder.append(address.getStreet()).append(",").append(address.getCity()).append(",")
                                .append(address.getCountry());
                return builder.toString();
        }

}

AddressDeserializer.java

package com.sample.app.serializer;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.TreeNode;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.sample.app.model.Address;

public class AddressDeserializer extends JsonDeserializer<Address> {

        @Override
        public Address deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
                TreeNode node = jp.getCodec().readTree(jp);

                String addressStr = node.get("address").toString();

                return getAddress(addressStr);
        }

        private static Address getAddress(String addr) {
                Address address = new Address();

                String[] tokens = addr.split(",");
                address.setStreet(tokens[0]);
                address.setCity(tokens[1]);
                address.setCountry(tokens[2]);

                return address;
        }

}

App.java

package com.sample.app;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.sample.app.model.Address;
import com.sample.app.model.Employee;

public class App {

        public static void main(String args[]) throws JsonParseException, JsonMappingException, IOException {

                ObjectMapper mapper = new ObjectMapper();

                Address address = new Address();
                address.setCity("Bangalore");
                address.setStreet("Chowdeswari Street");
                address.setCountry("India");

                Employee emp = new Employee();
                emp.setFirstName("Rama Krishna");
                emp.setLastName("Gurram");
                emp.setAddress(address);

                String json = mapper.writeValueAsString(emp);

                Employee emp1 = mapper.readValue(json, Employee.class);

                System.out.println("Serialized Data : \n" + json);
                System.out.println("\nDeserialized Data : \n" + emp1);

        }

}

Run App.java, you will see below messages in console.

Serialized Data : 
{"firstName":"Rama Krishna","lastName":"Gurram","address":{"address":"Chowdeswari Street,Bangalore,India"}}

Deserialized Data : 
Employee [firstName=Rama Krishna, lastName=Gurram, address=Address [street="Chowdeswari Street, city=Bangalore, country=India"]]

Previous                                                    Next                                                    Home

Genson is an API, used to process JSON for Java and Scala languages. it is easy to use.

Following are the key features of Genson API.

         a. Convert Java object to JSON and Vice versa

         b. Full support of generic types, polymorphic types and immutable objects that don't provide a default constructor.

I copied following figure from Genson home page (http://owlike.github.io/genson/), seems to be this figure is interesting. It compares Jackson, Genson ad Gson libraries

In following posts, I am going to explain,

Convert Java object to Json

Convert JSON to Java object

Convert json to list of objects

Convert json to map

Exclude a property from serialization

Skip null values

Pretty json

Work with constructor with arguments

Object serialization and deserialization

Previous                                                 Next                                                 Home