Jackson: @JsonSerialize: Custom serialization

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"]]

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