Jackson Annotations - @JacksonInject

Overview

@JacksonInject annotation is used when a property value is to be injected instead of being parsed from Json input. In the example below, we are to insert a value into object instead of parsing from the Json.

Example - Deserialization without using @JacksonInject

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException; 
import java.text.ParseException; 

import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]) throws ParseException{ 
      String json = "{\"name\":\"Mark\"}"; 
      
      ObjectMapper mapper = new ObjectMapper();    
      try {
         Student student = mapper 
            .readerFor(Student.class) 
            .readValue(json); 
         System.out.println(student.rollNo +", " + student.name); 
      }
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }
}
class Student {
   public String name; 
   public int rollNo;  
}

Output

Run the JacksonTester and verify the output −

0, Mark

Example - Deserialization with @JacksonInject

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException; 
import java.text.ParseException; 

import com.fasterxml.jackson.annotation.JacksonInject; 
import com.fasterxml.jackson.databind.InjectableValues; 
import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]) throws ParseException{ 
      String json = "{\"name\":\"Mark\"}"; 
      InjectableValues injectableValues = new InjectableValues.Std() 
         .addValue(int.class, 1); 
      
      ObjectMapper mapper = new ObjectMapper();    
      try {
         Student student = mapper 
            .reader(injectableValues) 
            .forType(Student.class) 
            .readValue(json); 
         System.out.println(student.rollNo +", " + student.name); 
      }
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }
}
class Student {
   public String name; 
   @JacksonInject 
   public int rollNo;  
}

Output

Run the JacksonTester and verify the output −

1, Mark 

Here we can see, using @JacksonInject, we can a inject value in our object during deserialization easily.