Deep Dive jackson with Spring Boot

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sandeep negi
·

2 min read

  1. Create a Spring boot project

  2. Add a dependency

<dependency>  
   <groupId>com.fasterxml.jackson.core</groupId>  
   <artifactId>jackson-databind</artifactId>  
   <version>2.13.1</version>  
</dependency>
  1. Create a simple Pojo Class
package com.hashcodehub.springboot.studentservices.Model;  

import com.fasterxml.jackson.annotation.JsonProperty;  

public class Dog {  

    @JsonProperty("Doggy_Name")  
    private String dogName;  

    public Dog(){  

    }  
    public Dog(String dogName) {  
        this.dogName = dogName;  
    }  

    @Override  
    public String toString() {  
        return "Dog{" +  
                "dogName='" + dogName + '\'' +  
                '}';  
    }  

    public String getDogName() {  
        return dogName;  
    }  

    public void setDogName(String dogName) {  
        this.dogName = dogName;  
    }  
}
  1. Lets See all the functions in the main method
package com.hashcodehub.springboot.studentservices;  

import com.fasterxml.jackson.core.JsonProcessingException;  
import com.fasterxml.jackson.core.type.TypeReference;  
import com.fasterxml.jackson.databind.ObjectMapper;  
import com.hashcodehub.springboot.studentservices.Model.Dog;  
import org.springframework.boot.SpringApplication;  
import org.springframework.boot.autoconfigure.SpringBootApplication;  

import java.util.Arrays;  
import java.util.List;  

@SpringBootApplication  
public class StudentServicesApplication {  

   public static void main(String[] args) throws JsonProcessingException {  
      SpringApplication.run(StudentServicesApplication.class, args);  


      Dog d1 = new Dog("tommy");  
      ObjectMapper mapper = new ObjectMapper();  

      //writing Dog Object as String  
      String d1JsonString = mapper.writeValueAsString(d1);  


      System.out.println(d1JsonString);  


      //deserialize it  
      // make sure the model class contains the Default Contrustor otherwise there will be error      Dog d2= mapper.readValue(d1JsonString,Dog.class);  

      System.out.println(d2);  


      slash is added before the double quotes  
      String jsonStringModifiedPropertyName = "{\"dogName\":\"tommy\"}";  
      Dog d3= mapper.readValue(jsonStringModifiedPropertyName,Dog.class);  
      System.out.println(d3);  


      now deserialize if hte json string property name is different from the pojo classes  
      here the property name as smae as the @JsonProperty Name is the class Dog  
      String jsonStringModifiedPropertyName2 = "{\"Doggy_Name\":\"tommy\"}";  
      Dog d4= mapper.readValue(jsonStringModifiedPropertyName2,Dog.class);  
      System.out.println(d4);  


      // converting the jsonString Array of objects into a list  

      Dog d5 = new Dog("tommy");  
      Dog d6 = new Dog("sheru");  

      List<Dog> listOfDogObject = Arrays.asList(d5,d6);  
      ObjectMapper mapper5 = new ObjectMapper();  

      //writing Dog Object as String  
      String listOfDogString = mapper5.writeValueAsString(listOfDogObject);  
      System.out.println(listOfDogString);  


      List<Dog> listOfDog= mapper5.readValue(listOfDogString, new TypeReference<List<Dog>>() {  
      });  

      System.out.println(listOfDogString);  

      // we can also convert json string to a hashNap    
             Dog d1 = new Dog("tommy");  
      ObjectMapper mapper = new ObjectMapper();  

      //writing Dog Object as String  
      String d1JsonString = mapper.writeValueAsString(d1);  

    HashMap map= mapper.readValue(d1JsonString, new TypeReference<HashMap>() {  
    });  

    // we can use readTree to read the values from anyType of Json String 

      //jackson tree model if we are not aware of the type of model or json we are going to receive in that case we can use this generic model      //converting a json string to JsonNode      System.out.println(d1JsonString);  
//    JsonNode DogNode= mapper.valueToTree(d1JsonString);  
      JsonNode DogNode3=  mapper.readTree(d1JsonString);  

//    System.out.println(DogNode.get("dogName"));  
      System.out.println(DogNode3.isEmpty());  
      System.out.println(DogNode3.get("Doggy_Name"));


   }  

}
JavaSpringbootjackson