Type Handling Annotations in Jackson

Type Handling annotations are used for handling types of properties. Jackson provides more than one Type Handling annotations such as JsonTypeInfo, JsonSubTypes, and JsonTypeName. Type Handling annotation can be used at the time of serializing an object or deserializing a Json string.

Let’s understand each one of them one by one with an example to understand how these annotations are used for type handling.

@JsonTypeInfo

It is one of the most used Type Handling annotations which we used at the time of serializing an object. It is used for indicating the details of what type of information to include in serialization and deserialization.

Let’s take an example to understand how the annotation is used for getting the detail of information.

JsonTypeInfoExample.java

  // import required classes and package if any  import java.io.IOException;  import java.util.Scanner;    import com.fasterxml.jackson.annotation.JsonSubTypes;  import com.fasterxml.jackson.annotation.JsonTypeInfo;  import com.fasterxml.jackson.annotation.JsonTypeInfo.As;  import com.fasterxml.jackson.annotation.JsonTypeName;  import com.fasterxml.jackson.databind.ObjectMapper;    // create class JsonTypeInfoExample to understand the use of @JsonTypeInfo  public class JsonTypeInfoExample {            // main() method start      public static void main(String args[]) throws IOException {                    // create Scanner class object          Scanner sc= new Scanner(System.in);                    ShapeInfo shapeObj;                    String name;          Double radious;                    System.out.println(“Enter name of Circle:”);          name = sc.nextLine();                    System.out.println(“Enter radious of Circle:”);          radious = sc.nextDouble();                    // create an instance of Shape class          shapeObj = new JsonTypeInfoExample.CircleInfo(name, radious);                    // Serialize CircleInfo          String result = new ObjectMapper()              .writerWithDefaultPrettyPrinter()              .writeValueAsString(shapeObj);          System.out.println(result);                     // json string to de-serialize          String jsonString = “{“name”:”squareTest”,”length”:0.5, “type”:”square”}”;          System.out.println(“Json data to deserialize: “+jsonString);                    // use ObjectMapper class for deserializing json          SquareInfo square = new ObjectMapper().readerFor(ShapeInfo.class).readValue(jsonString);          System.out.println(square.name);                    // close Scanner class object          sc.close();                }            // create class ShapeInfo by using @JsonTypeInfo and @JsonSubTypes      @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = As.PROPERTY, property = “type”) @JsonSubTypes({          @JsonSubTypes.Type(value = SquareInfo.class, name = “square”),              @JsonSubTypes.Type(value = CircleInfo.class, name = “circle”)              })      static class ShapeInfo {          public String name;                     // parameterized constructor          ShapeInfo(String name){              this.name = name;          }      }            // create class CircleInfo that extend ShapeInfo      @JsonTypeName(“square”)      static class SquareInfo extends ShapeInfo {          public double length;                    // default constructor for setting default values          SquareInfo(){              this(null,0.0);          }                    // parameterized constructor to set user define values          SquareInfo(String name, double length){              super(name);              this.length = length;          }      }            // create class CircleInfo that extend Shape      @JsonTypeName(“circle”)      static class CircleInfo extends ShapeInfo {          public double circleRadius;                      // default constructor for setting default values          CircleInfo(){              this(null,0.0);          }                    // parameterized constructor to set user define values          CircleInfo(String circleName, double circleRadius) {              super(circleName);              this.circleRadius = circleRadius;          }      }  }  

Output:

@JsonSubTypes

It is another most used THandling annotation, which we also used at the time of serializing and deserializing an object. It is used for indicating subtypes of types annotated. The @JsonSubTypes annotation is used with @JsonTypeInfo annotation.

Let’s take an example to understand the use of annotation.

JsonSubTypesExample.java

  //import required classes and package if any  import java.io.IOException;  import java.util.Scanner;    import com.fasterxml.jackson.annotation.JsonSubTypes;  import com.fasterxml.jackson.annotation.JsonTypeInfo;  import com.fasterxml.jackson.annotation.JsonTypeInfo.As;  import com.fasterxml.jackson.annotation.JsonTypeName;  import com.fasterxml.jackson.databind.ObjectMapper;    //create class JsonSubTypesExample to understand the use of @JsonSubTypes  public class JsonSubTypesExample {            // main() method start      public static void main(String args[]) throws IOException {                    // create Scanner class object          Scanner sc= new Scanner(System.in);                    PersonInfo personObj;                    String name;          String id;                    System.out.println(“Enter Name of Student:”);          name = sc.nextLine();                    System.out.println(“Enter Student Id:”);          id = sc.nextLine();                    // create an instance of Person class          personObj = new JsonSubTypesExample.StudentInfo(name, id);                    // Serialize CircleInfo          String result = new ObjectMapper()              .writerWithDefaultPrettyPrinter()              .writeValueAsString(personObj);          System.out.println(result);                     // json string to de-serialize          String jsonString = “{“name”:”Sharon Lorenz”,”id”:”0121″, “type”:”faculty”}”;          System.out.println(“Json data to deserialize: “+jsonString);                    // use ObjectMapper class for deserializing json          FacultyInfo faculty = new ObjectMapper().readerFor(PersonInfo.class).readValue(jsonString);          System.out.println(faculty.name);                    // close Scanner class object          sc.close();                }            // create class PersonInfo by using @JsonTypeInfo and @JsonSubTypes      @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = As.PROPERTY, property = “type”) @JsonSubTypes({          @JsonSubTypes.Type(value = StudentInfo.class, name = “student”),              @JsonSubTypes.Type(value = FacultyInfo.class, name = “faculty”)              })      static class PersonInfo {          public String name;                     // parameterized constructor          PersonInfo(String name){              this.name = name;          }      }            // create class StudentInfo that extend PersonInfo      @JsonTypeName(“student”)      static class StudentInfo extends PersonInfo {          public String id;                    // default constructor for setting default values          StudentInfo(){              this(null, “”);          }                    // parameterized constructor to set user define values          StudentInfo(String name, String id){              super(name);              this.id = id;          }      }            // create class FacultyInfo that extend PersonInfo      @JsonTypeName(“faculty”)      static class FacultyInfo extends PersonInfo {          public String id;                      // default constructor for setting default values          FacultyInfo(){              this(null,””);          }                    // parameterized constructor to set user define values          FacultyInfo(String name, String id) {              super(name);              this.id = id;          }      }  }  

Output:

@JsonTypeName

It is another important Type Handling annotation, i.e., used for setting types name to be used for annotated class.

Let’s take an example to understand how the annotation works in Java:

JsonTypeNameExample.java

  // import required classes and package if any   import java.io.IOException;  import java.util.Scanner;    import com.fasterxml.jackson.annotation.JsonSubTypes;  import com.fasterxml.jackson.annotation.JsonTypeInfo;  import com.fasterxml.jackson.annotation.JsonTypeInfo.As;  import com.fasterxml.jackson.annotation.JsonTypeName;  import com.fasterxml.jackson.databind.ObjectMapper;    // create class JsonTypeNameExample to understand the use of @JsonTypeName  public class JsonTypeNameExample {            // main() method start      public static void main(String args[]) throws IOException {                    // create Scanner class object          Scanner sc= new Scanner(System.in);                    ShapeInfo shapeObj;                    String name;          Double radious;                    System.out.println(“Enter name of Circle:”);          name = sc.nextLine();                    System.out.println(“Enter radious of Circle:”);          radious = sc.nextDouble();                    // create an instance of Shape class          shapeObj = new JsonTypeNameExample.CircleInfo(name, radious);                    // Serialize CircleInfo          String result = new ObjectMapper()              .writerWithDefaultPrettyPrinter()              .writeValueAsString(shapeObj);          System.out.println(result);                     // json string to de-serialize          String jsonString = “{“name”:”squareTest”,”length”:0.5, “type”:”square”}”;          System.out.println(“Json data to deserialize: “+jsonString);                    // use ObjectMapper class for deserializing json          SquareInfo square = new ObjectMapper().readerFor(ShapeInfo.class).readValue(jsonString);          System.out.println(square.name);                    // close Scanner class object          sc.close();                }            // create class ShapeInfo by using @JsonTypeInfo and @JsonSubTypes      @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = As.PROPERTY, property = “type”) @JsonSubTypes({          @JsonSubTypes.Type(value = SquareInfo.class, name = “square”),              @JsonSubTypes.Type(value = CircleInfo.class, name = “circle”)              })      static class ShapeInfo {          public String name;                     // parameterized constructor          ShapeInfo(String name){              this.name = name;          }      }            // create class CircleInfo that extend ShapeInfo      @JsonTypeName(“square”)      static class SquareInfo extends ShapeInfo {          public double length;                    // default constructor for setting default values          SquareInfo(){              this(null,0.0);          }                    // parameterized constructor to set user define values          SquareInfo(String name, double length){              super(name);              this.length = length;          }      }            // create class CircleInfo that extend Shape      @JsonTypeName(“circle”)      static class CircleInfo extends ShapeInfo {          public double circleRadius;                      // default constructor for setting default values          CircleInfo(){              this(null,0.0);          }                    // parameterized constructor to set user define values          CircleInfo(String circleName, double circleRadius) {              super(circleName);              this.circleRadius = circleRadius;          }      }  }  

Output:

Next TopicGeneral Annotations in Jackson

Type Handling Annotations in Jackson

Type Handling Annotations in Jackson

@JsonTypeInfo

@JsonSubTypes

@JsonTypeName

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