Jackson Annotations - @JsonAnySetter

Overview

@JsonAnySetter annotation allows a setter method to use Map which is then used to deserialize the additional properties of JSON in the similar fashion as other properties.

Example - Deserialization without using @JsonAnySetter

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException; 
import java.util.HashMap; 
import java.util.Map; 

import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]){ 
      ObjectMapper mapper = new ObjectMapper(); 
      String jsonString = "{\"RollNo\" : \"1\",\"Name\" : \"Mark\"}"; 
      try { 
         Student student = mapper.readerFor(Student.class).readValue(jsonString); 
         System.out.println(student.getProperties().get("Name")); 
         System.out.println(student.getProperties().get("RollNo")); 
      }
      catch (IOException e) {
         e.printStackTrace(); 
      } 
   }
}
class Student {
   private Map<String, String> properties; 
   public Student(){ 
      properties = new HashMap<>(); 
   }  
   public Map<String, String> getProperties(){ 
      return properties; 
   } 
   public void add(String property, String value){ 
      properties.put(property, value); 
   }   
}

Output

Run the JacksonTester and verify the output −

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "RollNo" (class com.tutorialspoint.Student), not marked as ignorable (one known property: "properties"])
 at [Source: REDACTED ('StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION' disabled); line: 1, column: 14] (through reference chain: com.tutorialspoint.Student["RollNo"])
	at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:61)
	at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:1207)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:2295)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1823)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1801)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:308)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:169)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:342)
	at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:2130)
	at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1565)
	at com.tutorialspoint.JacksonTester.main(JacksonTester.java:14)

Example - Deserialization with @JsonAnySetter

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException; 
import java.util.HashMap; 
import java.util.Map; 

import com.fasterxml.jackson.annotation.JsonAnySetter; 
import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]){ 
      ObjectMapper mapper = new ObjectMapper(); 
      String jsonString = "{\"RollNo\" : \"1\",\"Name\" : \"Mark\"}"; 
      try { 
         Student student = mapper.readerFor(Student.class).readValue(jsonString); 
         System.out.println(student.getProperties().get("Name")); 
         System.out.println(student.getProperties().get("RollNo")); 
      }
      catch (IOException e) {
         e.printStackTrace(); 
      } 
   }
}
class Student {
   private Map<String, String> properties; 
   public Student(){ 
      properties = new HashMap<>(); 
   }  
   public Map<String, String> getProperties(){ 
      return properties; 
   } 
   @JsonAnySetter 
   public void add(String property, String value){ 
      properties.put(property, value); 
   }   
}

Output

Run the JacksonTester and verify the output −

Mark 
1 

Here we can see, without using @JsonAnySetter, we get the exception during deserialization. Using @JsonAnySetter annotation, we can use map as properties of an object.