Jackson: Handling enums

By default Jackson use, name() method of enum to serialize and deserialize the information.

Month.java

package com.sample.app.model;

public enum Month {
 SUNDAY("Sunny Sunday"), MONDAY("Morning Monday"), TUESDAY("Good tuesday"), WEDNESDAY("Happy Wednesday"),
 THURSDAY("Great Tuesday"), FRIDAY("Good Friday"), SATURDAY("Sleepy Saturday");

 private String data;

 Month(String data) {
  this.data = data;
 }

 public String getData() {
  return data;
 }

 public void setData(String data) {
  this.data = data;
 }

}

Employee.java

package com.sample.app.model;

public class Employee {
 private String firstName;
 private String lastName;
 private Month monthOfBirth;

 public Employee() {

 }

 public Employee(String firstName, String lastName, Month monthOfBirth) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.monthOfBirth = monthOfBirth;
 }

 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 Month getMonthOfBirth() {
  return monthOfBirth;
 }

 public void setMonthOfBirth(Month monthOfBirth) {
  this.monthOfBirth = monthOfBirth;
 }

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

}

App.java

package com.sample.app;

import com.sample.app.model.Employee;
import com.sample.app.model.Month;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class App {

 public static void main(String args[]) throws JsonGenerationException, JsonMappingException, IOException {
  Employee emp1 = new Employee("Rama Krishna", "Gurram", Month.TUESDAY);

  ObjectMapper mapper = new ObjectMapper();
  String json = mapper.writeValueAsString(emp1);
  System.out.println("Serialized Data :\n" + json + "\n");

  Employee emp2 = mapper.readValue(json, Employee.class);
  System.out.println("DeSerialized Data :\n" + emp2 + "\n");

 }

}

Output

Serialized Data :
{"firstName":"Rama Krishna","lastName":"Gurram","monthOfBirth":"TUESDAY"}

DeSerialized Data :
Employee [firstName=Rama Krishna, lastName=Gurram, monthOfBirth=TUESDAY]

Customize serialization and deserialization

By providing custom serializer and deserializer you can customize serialization process.

Create MonthSerializer and MonthDeserializer classes.

MonthSerializer.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.Month;

public class MonthSerializer extends JsonSerializer<Month> {

 @Override
 public void serialize(Month month, JsonGenerator gen, SerializerProvider serializers)
   throws IOException, JsonProcessingException {
  gen.writeStartObject();
  gen.writeStringField("monthOfBirth", month.getData());
  gen.writeEndObject();

 }

}

MonthDeserializer.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.Month;

public class MonthDeserializer extends JsonDeserializer<Month> {

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

  String monthOfBirth = node.get("monthOfBirth").toString();
  
  // REMOVE DOUBLE QUOTES
  monthOfBirth = monthOfBirth.substring(1, monthOfBirth.length()-1);

  if (monthOfBirth.equals(Month.SUNDAY.getData())) {
   return Month.SUNDAY;
  } else if (monthOfBirth.equals(Month.MONDAY.getData())) {
   return Month.MONDAY;
  } else if (monthOfBirth.equals(Month.TUESDAY.getData())) {
   return Month.TUESDAY;
  } else if (monthOfBirth.equals(Month.WEDNESDAY.getData())) {
   return Month.WEDNESDAY;
  } else if (monthOfBirth.equals(Month.THURSDAY.getData())) {
   return Month.THURSDAY;
  } else if (monthOfBirth.equals(Month.FRIDAY.getData())) {
   return Month.FRIDAY;
  } else {
   return Month.SATURDAY;
  }

 }

}

Create custom module and register serializer, deserializers.

MonthModule.java

package com.sample.app.serializer;

import com.fasterxml.jackson.core.util.VersionUtil;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.sample.app.model.Month;

public class MonthModule extends SimpleModule{
     private static final long serialVersionUID = 1L;
     
     private static final String NAME = "CustomAddressModule";
     private static final VersionUtil VERSION_UTIL = new VersionUtil() {
     };

     public MonthModule() {
             super(NAME, VERSION_UTIL.version());
             addSerializer(Month.class, new MonthSerializer());
             addDeserializer(Month.class, new MonthDeserializer());
     }
}

App.java

package com.sample.app;

import com.sample.app.model.Employee;
import com.sample.app.model.Month;
import com.sample.app.serializer.MonthModule;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class App {

 public static void main(String args[]) throws JsonGenerationException, JsonMappingException, IOException {
  Employee emp1 = new Employee("Rama Krishna", "Gurram", Month.TUESDAY);

  ObjectMapper mapper = new ObjectMapper();
  mapper.registerModule(new MonthModule());

  String json = mapper.writeValueAsString(emp1);
  System.out.println("Serialized Data :\n" + json + "\n");

  Employee emp2 = mapper.readValue(json, Employee.class);
  System.out.println("DeSerialized Data :\n" + emp2 + "\n");

 }

}

Output

Serialized Data :
{"firstName":"Rama Krishna","lastName":"Gurram","monthOfBirth":{"monthOfBirth":"Good tuesday"}}

DeSerialized Data :
Employee [firstName=Rama Krishna, lastName=Gurram, monthOfBirth=TUESDAY]

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