Serialize and Deserialize Booleans as Integers with Jackson

In Java, the Jackson library is the de-facto standard when it comes to processing JSON. In order to map a Boolean value to an integer value, Jackson’s well-defined defaults are not sufficient, and for that, we need to perform manual configuration.

In this section, we will understand how we can serialize Boolean values as Integers, numeric strings, and vice versa.

Let’s understand the serialization and deserialization one by one:

Serialization

As we already mentioned that Jackson’s well-defined defaults are not sufficient to map Boolean values to Integer values. So, we will perform manual configuration, i.e., Field Level Configuration and Global Configuration. Let’s understand both types of configuration one by one.

Field Level Configuration

We have one simple way of serializing Boolean into Integer by annotating our Boolean fields with @JsonFormat. We set the Shape with the Shape.Number in the following way:

  @JsonFormat(shape = Shape.NUMBER)  private Boolean passed;  @JsonFormat(shape = Shape.NUMBER)  private Boolean fail;  

Let’s take an example to understand how we can serialize Booleans into Integers.

SerializeBooleansAsIntegerExample1.java

  // import required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.annotation.JsonFormat;  import com.fasterxml.jackson.annotation.JsonFormat.Shape;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.ObjectMapper;    // create class SerializeBooleanAsIntegerExample1 to serialize java object by mapping Boolean as Integer  public class SerializeBooleanAsIntegerExample1 {    // main() method start  public static void main(String args[]) throws JsonProcessingException {    String id, name, status;  Boolean passed = false, fail = false;    // create an instance of Scanner class  Scanner sc = new Scanner(System.in);    System.out.println(“Enter Student Id: “);  id = sc.nextLine();    System.out.println(“Enter Student Name: “);  name = sc.nextLine();    System.out.println(“Is “+name+ “pass in exams(Yes/No)?: “);  status = sc.nextLine();    if(status.equals(“Yes”)) {  passed = true;  }    if(status.equals(“No”)) {  fail = false;  }    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name, passed, fail);    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            //serialize Student object to JSON      String jsonString = mapper.writeValueAsString(std);            System.out.println(“Java object after serializing:”+jsonString);  }    }  class Student {        private String stdId;      private String stdName;            @JsonFormat(shape = Shape.NUMBER)      private Boolean passed;            @JsonFormat(shape = Shape.NUMBER)      private Boolean fail;        public Student(String stdId, String stdName, Boolean passed, Boolean fail) {      this.stdId = stdId;      this.stdName = stdName;      this.passed = passed;      this.fail = fail;      }            public String getStdId() {      return stdId;      }            public String getStdName() {      return stdName;      }           public Boolean getPassed() {      return passed;      }           public Boolean getFail() {      return fail;      }        }  

Output:

Serialize and Deserialize Booleans as Integers with Jackson

Global Configuration

Sometimes, it is not possible to annotate each and every field. So, we use the concept of Global Configuration to configure Boolean to Integer serialization globally. Jackson allows us to globally configure @JsonFormat annotation by overriding the defaults in ObjectMapper class.

Let’s take an example to understand how to serialize Booleans into Integer by configure ObjectMapper class globally.

SerializeBooleanAsIntegerExample2.java

  //import required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.annotation.JsonFormat;  import com.fasterxml.jackson.annotation.JsonFormat.Shape;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.ObjectMapper;    //create class SerializeBooleanAsIntegerExample2 to serialize java object by mapping Boolean as Integer globally  public class SerializeBooleanAsIntegerExample2 {    // main() method start  public static void main(String args[]) throws JsonProcessingException {    String id, name, status;  Boolean passed = false, fail = false;    // create an instance of Scanner class  Scanner sc = new Scanner(System.in);    System.out.println(“Enter Student Id: “);  id = sc.nextLine();    System.out.println(“Enter Student Name: “);  name = sc.nextLine();    System.out.println(“Is “+name+ “pass in exams(Yes/No)?: “);  status = sc.nextLine();    if(status.equals(“Yes”)) {  passed = true;  }    if(status.equals(“No”)) {  fail = true;  }    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name, passed, fail);    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // configure ObjectMapper globally      mapper.configOverride(Boolean.class)      .setFormat(JsonFormat.Value.forShape(Shape.NUMBER));            //serialize Student object to JSON      String jsonString = mapper.writeValueAsString(std);            System.out.println(“Java object after serializing:”+jsonString);  }    }  class Student {    private String stdId;  private String stdName;  private Boolean passed;  private Boolean fail;    public Student(String stdId, String stdName, Boolean passed, Boolean fail) {  this.stdId = stdId;  this.stdName = stdName;  this.passed = passed;  this.fail = fail;  }     public String getStdId() {  return stdId;  }     public String getStdName() {  return stdName;  }     public Boolean getPassed() {  return passed;  }     public Boolean getFail() {  return fail;  }     }  

Output:

Serialize and Deserialize Booleans as Integers with Jackson

Deserialization

Just like serialization, we also need to perform deserialization of a string having values 0 and 1 for Boolean variables. So, we need to obtain Boolean values from Integers at the time of deserializing JSON strings into our models.

There is no need to use @JsonFormat annotation or any configuration for parsing Integers to Boolean because Jackson, by default, performs this task for us.

Let’s take an example to understand how deserialization is done:

DeserializeIntegerIntoBooleanExample.java

  //import  required classes and package if any  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.JsonMappingException;  import com.fasterxml.jackson.databind.ObjectMapper;  //create class DeserializeIntegerIntoBooleanExample to deserialize JSON string into pojo  public class DeserializeIntegerIntoBooleanExample {    // main() method start  public static void main(String args[]) throws JsonMappingException, JsonProcessingException{    // JSON string to parse  String jsonString = “{“stdId”:”121″, “stdName”:”Nicholas”, “passed”:1, “fail”:0}”;    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // deserialize JSON string into Java object      Student std = mapper.readValue(jsonString, Student.class);        // print student Id and Name      System.out.println(“Student Id: “+std.getStdId());      System.out.println(“Student Name: “+std.getStdName());      System.out.println(“is student passed?: “+std.getPassed());      System.out.println(“is student fail?: “+std.getFail());  }    }    class Student {    private String stdId;  private String stdName;  private Boolean passed;  private Boolean fail;    public Student() {  this.stdId = null;  this.stdName = null;  this.passed = null;  this.fail = null;  }    public Student(String stdId, String stdName, Boolean passed, Boolean fail) {  this.stdId = stdId;  this.stdName = stdName;  this.passed = passed;  this.fail = fail;  }     public String getStdId() {  return stdId;  }     public String getStdName() {  return stdName;  }     public Boolean getPassed() {  return passed;  }     public Boolean getFail() {  return fail;  }     }  

Output:

Serialize and Deserialize Booleans as Integers with Jackson

Numeric Strings Instead of Integers

Many times, we need to serialize/deserialize Boolean values into numeric strings. Let’s understand serialization and deserialization one by one:

Serializing into Numeric Strings

In order to serialize Booleans into Numeric strings, we need to create a custom serializer, and then we use it for serializing Booleans into Numeric strings.

Let’s first create a custom serializer, i.e., NumericStringSerializer, and then we will take an example in which we use this custom serializer for serializing Booleans into numeric strings.

NumericStringSerializer.java

  // import required classes and package  import java.io.IOException;  import com.fasterxml.jackson.core.JsonGenerator;  import com.fasterxml.jackson.databind.JsonSerializer;  import com.fasterxml.jackson.databind.SerializerProvider;    // create custom serializer NumericStringSerializer by using JsonSerializer  public class NumericStringSerializer extends JsonSerializer {    // override serialize() method of JsonSerializer      @Override      public void serialize(Boolean boolValue, JsonGenerator generator, SerializerProvider provider)  throws IOException {            // use writeString() method of JsonGenerator to parse boolean to numeric string      generator.writeString(boolValue ? “1” : “0”);      }  }  

SerializeBooleanToNumericString.java

  //import required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.ObjectMapper;  import com.fasterxml.jackson.databind.annotation.JsonSerialize;    //create class SerializeBooleanToNumericString to serialize java object by mapping Boolean as a numeric string  public class SerializeBooleanToNumericString {    // main() method start  public static void main(String args[]) throws JsonProcessingException {    String id, name, status;  Boolean passed = false, fail = false;    // create an instance of Scanner class  Scanner sc = new Scanner(System.in);    System.out.println(“Enter Student Id: “);  id = sc.nextLine();    System.out.println(“Enter Student Name: “);  name = sc.nextLine();    System.out.println(“Is “+name+ “pass in exams(Yes/No)?: “);  status = sc.nextLine();    if(status.equals(“Yes”)) {  passed = true;  }    if(status.equals(“No”)) {  fail = true;  }    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name, passed, fail);    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            //serialize Student object to JSON      String jsonString = mapper.writeValueAsString(std);            System.out.println(“Java object after serializing:”+jsonString);  }    }  class Student {    private String stdId;  private String stdName;     @JsonSerialize(using = NumericStringSerializer.class)  private Boolean passed;     @JsonSerialize(using = NumericStringSerializer.class)  private Boolean fail;    public Student(String stdId, String stdName, Boolean passed, Boolean fail) {  this.stdId = stdId;  this.stdName = stdName;  this.passed = passed;  this.fail = fail;  }     public String getStdId() {  return stdId;  }     public String getStdName() {  return stdName;  }     public Boolean getPassed() {  return passed;  }     public Boolean getFail() {  return fail;  }   }  

Output:

Serialize and Deserialize Booleans as Integers with Jackson

Deserializing from Numeric Strings

Just like serializing, for deserializing, we also use a custom deserializer. We will create a custom deserializer, and then we will use it for deserializing Numeric strings into Booleans.

Let’s first create a custom deserializer, i.e., NumericStringDeserializer, and then we will take an example in which we use this custom deserializer for deserializing numeric strings into Booleans.

NumericStringDeserializer.java

  //import required classes and package  import java.io.IOException;  import com.fasterxml.jackson.core.JacksonException;  import com.fasterxml.jackson.core.JsonParser;  import com.fasterxml.jackson.databind.DeserializationContext;  import com.fasterxml.jackson.databind.JsonDeserializer;    //create custom deserializer NumericStringDeserializer by using JsonDeserializer  public class NumericStringDeserializer extends JsonDeserializer {    // override deserialize() method of JsonDeserializer  @Override  public Boolean deserialize(JsonParser parser, DeserializationContext ctxt) throws IOException, JacksonException {    // return true or false by comparing strings  if(parser.getText().equals(“0”)) {  return Boolean.FALSE;  }  if(parser.getText().equals(“1”)) {  return Boolean.TRUE;  }  return null;  }    }  

DeserializeNumericStringToBoolean.java

  //import  required classes and package if any  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.JsonMappingException;  import com.fasterxml.jackson.databind.ObjectMapper;  import com.fasterxml.jackson.databind.annotation.JsonDeserialize;    //create class DeserializeNumericStringToBoolean to deserialize JSON string into pojo  public class DeserializeNumericStringToBoolean {    // main() method start  public static void main(String args[]) throws JsonMappingException, JsonProcessingException{    // JSON string to parse  String jsonString = “{“stdId”:”121″, “stdName”:”Nicholas”, “passed”:”1″, “fail”:”0″}”;    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // deserialize JSON string into Java object      Student std = mapper.readValue(jsonString, Student.class);        // print student Id and Name      System.out.println(“Student Id: “+std.getStdId());      System.out.println(“Student Name: “+std.getStdName());      System.out.println(“is student passed?: “+std.getPassed());      System.out.println(“is student fail?: “+std.getFail());  }    }    class Student {    private String stdId;  private String stdName;    @JsonDeserialize(using = NumericStringDeserializer.class)  private Boolean passed;    @JsonDeserialize(using = NumericStringDeserializer.class)  private Boolean fail;    public Student() {  this.stdId = null;  this.stdName = null;  this.passed = null;  this.fail = null;  }    public Student(String stdId, String stdName, Boolean passed, Boolean fail) {  this.stdId = stdId;  this.stdName = stdName;  this.passed = passed;  this.fail = fail;  }    public String getStdId() {  return stdId;  }    public String getStdName() {  return stdName;  }    public Boolean getPassed() {  return passed;  }    public Boolean getFail() {  return fail;  }    }  

Output:

Serialize and Deserialize Booleans as Integers with Jackson

Next TopicDeserialize to Collection/Array in Jackson

Serialize and Deserialize Booleans as Integers with Jackson

Serialize and Deserialize Booleans as Integers with Jackson

Serialization

Field Level Configuration

Global Configuration

Deserialization

Numeric Strings Instead of Integers

Serializing into Numeric Strings

Deserializing from Numeric Strings

How to Write a Check

3N+1 Problem in Java

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