Jackson Annotations - @JsonDeserialize

Overview

@JsonDeserialize annotation is used to specify custom deserializer to unmarshall the json object.

Example - Deserialization without using @JsonDeserialize

JacksonTester.java

package com.tutorialspoint;

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

import com.fasterxml.jackson.databind.ObjectMapper; 

public class JacksonTester {
   public static void main(String args[]) throws ParseException{ 
      ObjectMapper mapper = new ObjectMapper(); 
      String jsonString = "{\"name\":\"Mark\",\"dateOfBirth\":\"20-12-1984\"}"; 
      try {     
         Student student = mapper
            .readerFor(Student.class) 
            .readValue(jsonString); 
         System.out.println(student.dateOfBirth); 
      } 
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }
}
class Student {
   public String name; 
   public Date dateOfBirth; 
}

Output

Run the JacksonTester and verify the output −

com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type 'java.util.Date' from String "20-12-1984": not a valid representation (error: Failed to parse Date value '20-12-1984': Cannot parse date "20-12-1984": not compatible with any of standard forms ("yyyy-MM-dd'T'HH:mm:ss.SSSX", "yyyy-MM-dd'T'HH:mm:ss.SSS", "EEE, dd MMM yyyy HH:mm:ss zzz", "yyyy-MM-dd"))
 at [Source: REDACTED ('StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION' disabled); line: 1, column: 30] (through reference chain: com.tutorialspoint.Student["dateOfBirth"])
	at com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.weirdStringException(DeserializationContext.java:2013)
	at com.fasterxml.jackson.databind.DeserializationContext.handleWeirdStringValue(DeserializationContext.java:1299)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:1426)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:1368)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateBasedDeserializer._parseDate(DateDeserializers.java:200)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:302)
	at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:280)
	at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:137)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:302)
	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:16)

Example - Deserialization with @JsonDeserialize

JacksonTester.java

package com.tutorialspoint;

import java.io.IOException; 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 

import com.fasterxml.jackson.core.JsonParser; 
import com.fasterxml.jackson.core.JsonProcessingException; 
import com.fasterxml.jackson.databind.DeserializationContext; 
import com.fasterxml.jackson.databind.ObjectMapper; 
import com.fasterxml.jackson.databind.annotation.JsonDeserialize; 
import com.fasterxml.jackson.databind.deser.std.StdDeserializer; 

public class JacksonTester {
   public static void main(String args[]) throws ParseException{ 
      ObjectMapper mapper = new ObjectMapper(); 
      String jsonString = "{\"name\":\"Mark\",\"dateOfBirth\":\"20-12-1984\"}"; 
      try {     
         Student student = mapper
            .readerFor(Student.class) 
            .readValue(jsonString); 
         System.out.println(student.dateOfBirth); 
      } 
      catch (IOException e) { 
         e.printStackTrace(); 
      }   
   }
}
class Student {
   public String name; 
   @JsonDeserialize(using = CustomDateDeserializer.class) 
   public Date dateOfBirth; 
}
class CustomDateDeserializer extends StdDeserializer<Date> {
   private static final long serialVersionUID = 1L;
   private static SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
   public CustomDateDeserializer() { 
      this(null); 
   } 
   public CustomDateDeserializer(Class t) { 
      super(t); 
   } 
   @Override 
   public Date deserialize(JsonParser parser, DeserializationContext context) 
      throws IOException, JsonProcessingException { 
      
      String date = parser.getText(); 
      try { 
         return formatter.parse(date); 
      } 
      catch (ParseException e) { 
         e.printStackTrace(); 
      }    
      return null; 
   }   
}

Output

Run the JacksonTester and verify the output −

Thu Dec 20 00:00:00 IST 1984

Here we can see, without using @JsonDeserialize, Jackson is unable to handle string deserialization to date. Using @JsonDeserialize we can define and set a custom deserializer for us.