Jackson JSON Views

JSON Views is another important element of Jackson. JSON Views is also used for serializing and deserializing Java objects. We use @JsonView annotation for customizing the view at the time of serializing/deserializing.

In this section, we will understand how we can perform serialization/deserialization using JSON Views and how we can customize the view.

Serialize Using JSON Views

In order to serialize an object by using @JsonView, we first create a view, and then we will use it for serialization. Let’s take an example to understand how we can use JSON View to serialize an object.

JSONViewExample1.java

  // import  required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.annotation.JsonView;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.MapperFeature;  import com.fasterxml.jackson.databind.ObjectMapper;    // create class JSONViewExample1 to serialize an object using JSON View  public class JSONViewExample1 {  // main() method start  @SuppressWarnings(“deprecation”)  public static void main(String args[]) throws JsonProcessingException {  String id, name;  // 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();    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name);    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // disable DEFAULT_VIEW_INCLUSION mapper feature      mapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);        String result = mapper      .writerWithView(Views.Public.class)      .writeValueAsString(std);            System.out.println(“Java object after serializing:”+result);    }    }    // create class Student  class Student {    // instance variable      public String stdId;        // instance variable with @JsonView      @JsonView(Views.Public.class)      public String stdName;            // default constructor      Student(){      this.stdId = null;      this.stdName = null;      }            // parameterized constructor      Student(String stdId, String stdName){      this.stdId = stdId;      this.stdName = stdName;      }  }    // create class for View  class Views {  // create class public      public static class Public {      }  }  

Output:

Jackson JSON Views

By using multiple JSON Views, we can also serialize an object in Java. Here, we create a view where the Internal view extends to the Public one. So, the Views class looks like this:

  public class Views {  public static class Public {      }        public static class Internal extends Public {      }  }  

We will modify the Student class. In the Student class, stdId and stdName fields will be included in the Public view. We create a new field, i.e., the course which will be included in the Internal view. So, our Student class looks like this:

  public class Student{         @JsonView(Views.Public.class)      public int stdId;        @JsonView(Views.Public.class)      public String stdName;        @JsonView(Views.Internal.class)      public String course;  }  

Now, let’s take an example to understand how, we can serialize an object using multiple JSON Views:

JSONViewExample2.java

  //import  required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.annotation.JsonView;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.MapperFeature;  import com.fasterxml.jackson.databind.ObjectMapper;    //create class JSONViewExample2 to serialize an object using multiple JSON Views  public class JSONViewExample2 {    // main() method start  @SuppressWarnings(“deprecation”)  public static void main(String args[]) throws JsonProcessingException {    String id, name, course;    // 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(“Enter Course Name: “);  course = sc.nextLine();    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name, course);    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // disable DEFAULT_VIEW_INCLUSION mapper feature      mapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);        String result = mapper      .writerWithView(Views.Public.class)      .writeValueAsString(std);            System.out.println(“Java object after serializing:”+result);    }    }    //create class Student  class Student {    @JsonView(Views.Public.class)  public String stdId;    @JsonView(Views.Public.class)  public String stdName;    @JsonView(Views.Internal.class)  public String course;     // default constructor  Student(){  this.stdId = null;  this.stdName = null;  this.course = null;  }     // parameterized constructor  Student(String stdId, String stdName, String course){  this.stdId = stdId;  this.stdName = stdName;  this.course = course;  }  }    //create class for View  class Views {  public static class Public {        }    public static class Internal extends Public {        }  }  

Output:

Jackson JSON Views

Deserialize using JSON Views

Just like serialization, we can also deserialize JSON strings into Java objects by using JSON Views. Let’s take an example to understand how deserialization is done by using JSON Views.

JSONViewExample3.java

  //import  required classes and package if any  import com.fasterxml.jackson.annotation.JsonView;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.JsonMappingException;  import com.fasterxml.jackson.databind.ObjectMapper;    //create class JSONViewExample3 to deserialize JSON string into POJO by using JSON Views  public class JSONViewExample3 {    // main() method start  public static void main(String args[]) throws JsonMappingException, JsonProcessingException{    // JSON string to parse  String jsonString = “{“stdId”:”121″, “stdName”:”Nicholas”}”;    // create an instance of ObjectMapper class      ObjectMapper mapper = new ObjectMapper();            // deserialize JSON string in Java object by using Jackson View      Student std = mapper      .readerWithView(Views.Public.class)      .forType(Student.class)      .readValue(jsonString);        // print student Id and Name      System.out.println(“Student Id: “+std.stdId);      System.out.println(“Student Name: “+std.stdName);  }    }    //create class Student  class Student {    // instance variable  public String stdId;    // instance variable with @JsonView  @JsonView(Views.Public.class)  public String stdName;     // default constructor  Student(){  this.stdId = null;  this.stdName = null;  }     // parameterized constructor  Student(String stdId, String stdName){  this.stdId = stdId;  this.stdName = stdName;  }  }    //create class for View  class Views {  // create class public  public static class Public {  }  }  

Output:

Jackson JSON Views

Serialize using the customize JSON Views

We can also Java objects by using the customize JSON View. In order to serialize Java objects by using the customize JSON View, we first customize the JSON view by using BeanPropertyWriter. We create the 65UpperCasingWriter class by extending BeanPropertyWriter for transforming the student name to upper case.

Let’s create the UpperCasingWriter class for transforming the student name to upper case.

UpperCasingWriter.java

  import com.fasterxml.jackson.core.JsonGenerator;  import com.fasterxml.jackson.databind.SerializerProvider;  import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;    // create class UpperCasingWriter to transform student name to upper case  public class UpperCasingWriter extends BeanPropertyWriter {    // create a variable of type BeanPropertyWriter      BeanPropertyWriter writer;        // parameterized constructor of UpperCasingWriter      public UpperCasingWriter(BeanPropertyWriter writer) {                super(writer);          this.writer = writer;      }        // override serializeAsField() method of BeanPropertyWriter      @Override      public void serializeAsField(Object bean, JsonGenerator generator, SerializerProvider provider) throws Exception {            // get student name from Object and store it to a variable of type String          String name = ((Student) bean).stdName;                    // change name to upper case if it is not null          name = (name == null) ? “” : name.toUpperCase();                    // write stdName in JSON by using generator          generator.writeStringField(“stdName”, name);      }  }  

Now, we will create a custom modifier to set the student name BeanPropertyWriter with our CustomCasingWriter.

CustomBeanSerializerModifier.java

  // import required classes and package if any  import java.util.List;  import com.fasterxml.jackson.databind.BeanDescription;  import com.fasterxml.jackson.databind.SerializationConfig;  import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;  import com.fasterxml.jackson.databind.ser.BeanSerializerModifier;    // create class CustomBeanSerializerModifier to set the student name BeanPropertyWriter with our custom UpperCasingWriter  public class CustomBeanSerializerModifier extends BeanSerializerModifier{    // override changeProperties method of BeanSerializerModifier      @Override      public List changeProperties( SerializationConfig configObj, BeanDescription beanDescObj,       List beanProperties) {            // use for loop for iterating bean properties      for (int i = 0; i < beanProperties.size(); i++) {            //get BeanPropertyWriter by using the get() method of List and store it into a variable of type BeanPropertyWriter      BeanPropertyWriter writer = beanProperties.get(i);            // check whether the writer name equals to stdName or not      if (writer.getName() == “stdName”) {            // set UpperCasingWriter by using set method                  beanProperties.set(i, new UpperCasingWriter(writer));              }          }      // return bean properties          return beanProperties;      }  }  

Let’s take an example to understand how serialization is done by using customize JSON View.

JSONViewExample4.java

  //import  required classes and package if any  import java.util.Scanner;  import com.fasterxml.jackson.annotation.JsonView;  import com.fasterxml.jackson.core.JsonProcessingException;  import com.fasterxml.jackson.databind.ObjectMapper;  import com.fasterxml.jackson.databind.ser.BeanSerializerFactory;  import com.fasterxml.jackson.databind.ser.SerializerFactory;    //create class JSONViewExample4 to serialize an object using the customize JSON Views  public class JSONViewExample4 {    // main() method start  public static void main(String args[]) throws JsonProcessingException {    String id, name, course;    // 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(“Enter Course Name: “);  course = sc.nextLine();    // close Scanner class object  sc.close();    // create Student object  Student std = new Student(id, name, course);    // create an instance of SerializerFactory by using BeanSerializerFactory and CustomBeanSerializerModifier  SerializerFactory factory = BeanSerializerFactory.instance  .withSerializerModifier(new CustomBeanSerializerModifier());    // create an instance of ObjectMapper class  ObjectMapper mapper = new ObjectMapper();    // set serializer factory to the maaper      mapper.setSerializerFactory(factory);        String jsonString = mapper.writerWithView(Views.Public.class).writeValueAsString(std);            System.out.println(“Java object after serializing: “+jsonString);    }    }    //create class Student  class Student {    @JsonView(Views.Public.class)  public String stdId;    @JsonView(Views.Public.class)  public String stdName;    @JsonView(Views.Internal.class)  public String course;    // default constructor  Student(){  this.stdId = null;  this.stdName = null;  this.course = null;  }    // parameterized constructor  Student(String stdId, String stdName, String course){  this.stdId = stdId;  this.stdName = stdName;  this.course = course;  }  }    //create class for View  class Views {  public static class Public {      }    public static class Internal extends Public {      }  }  

Output:

Jackson JSON Views

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