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Java – How to convert YAML to an Object using ObjectMapper ?

December 30, 2022 SJ JSON/YAML/XML 0

In this article, we will discuss how to convert YAML file to an Object using ObjectMapper

1. Required libraries :

1.1 Maven Co-ordinates :

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<dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-yaml</artifactId>
            <version>2.13.4</version>
</dependency>

1.2 JAR files to download :

Download below jar files and include them in Project classpath –

1.3 Project class-path :

2. YAML file to an Object conversion :

In the below illustration, we will convert YAML file to Person object

  • Since we are converting YAML file contents to an Object therefore we need corresponding objects such as Person, Address and Item with default no-argument constructor otherwise an runtime exception will be thrown

Person.java

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package in.bench.resources.yaml.conversion;
 
import java.util.List;
 
public class Person {
 
    // member variables
    private String title;
    private String firstName;
    private String lastName;
    private Address address;
    private List<Item> items;
 
    // parameterized constructor
 
    // setters and getters
 
    // no-arg constrcutor
    public Person() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    // toString() method
    @Override
    public String toString() {
        return "Person [title=" + title
                + ", firstName=" + firstName
                + ", lastName=" + lastName
                + ",\n address=" + address
                + ",\n items=" + items
                + "]";
    }
}

Address.java

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package in.bench.resources.yaml.conversion;
 
public class Address {
 
    // member variables
    private String flatNumber;
    private String buildingName;
    private String plotNumber;
    private String sector;
    private String NodeName;
    private String city;
    private String state;
    private String country;
 
    // parameterized constructor
 
    // getters and setters
 
    // no-arg constructor
    public Address() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    // toString() method
    @Override
    public String toString() {
        return "Address [flatNumber=" + flatNumber
                + ", buildingName=" + buildingName
                + ", plotNumber=" + plotNumber
                + ", sector=" + sector
                + ", NodeName=" + NodeName
                + ", city=" + city
                + ", state=" + state
                + ", country=" + country
                + "]";
    }
}

Item.java

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package in.bench.resources.yaml.conversion;
 
public class Item {
 
    // member variables
    private String itemName;
    private String itemBoughtYear;
 
    // parameterized constructor
 
    // setters and getters
 
    // no-arg constructor
    public Item() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    // toString() method
    @Override
    public String toString() {
        return "Item [itemName=" + itemName
                + ", itemBoughtYear=" + itemBoughtYear
                + "]";
    }
}

2.1 Main class for YAML file to an Object conversion :

  • First, read the contents of the YAML file to a String
  • And then convert YAML file to Person object using readValue() method of ObjectMapper class by passing 2-arguments,
    • Contents read from the YAML file in String format
    • Corresponding class name of the YAML file contents to be converted, in this case Person.class
  • Note: a default no-arg constructor is explicitly required for the conversion

YAML file contents – Person.yaml :

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---
title: "Mr."
firstName: "Sam"
lastName: "Anton"
address:
  flatNumber: "BV-1025"
  buildingName: "Shivaji"
  plotNumber: "1093"
  sector: "Sector 19"
  city: "Bengaluru"
  state: "Karnataka"
  country: "India"
  nodeName: "South Bengaluru"
items:
- itemName: "Television"
  itemBoughtYear: "2014"
- itemName: "Washing Machine"
  itemBoughtYear: "2020"
- itemName: "Refrigerator"
  itemBoughtYear: "2011"
- itemName: "Grinder"
  itemBoughtYear: "2012"
- itemName: "Computer"
  itemBoughtYear: "2010"

YamlToObjectConversion.java

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package in.bench.resources.yaml.conversion;
 
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
 
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 
public class YamlToObjectConversion {
 
    public static void main(String[] args) {
 
        // create ObjectMapper to write to file
        ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
 
        try {
            String content = new String(Files.readAllBytes(Paths.get(
                    "C:\\Users\\Demo\\eclipse-workspace\\YamlConversion\\Person.yaml")));
 
            // read from file
            Person person = mapper.readValue(content, Person.class);
            System.out.println(person);
 
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

Output in console :

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Person [title=Mr., firstName=Sam, lastName=Anton,
 address=Address [flatNumber=BV-1025, buildingName=Shivaji, plotNumber=1093,
 sector=Sector 19, NodeName=South Bengaluru, city=Bengaluru,
 state=Karnataka, country=India],
 items=[Item [itemName=Television, itemBoughtYear=2014],
             Item [itemName=Washing Machine, itemBoughtYear=2020],
             Item [itemName=Refrigerator, itemBoughtYear=2011],
             Item [itemName=Grinder, itemBoughtYear=2012],
             Item [itemName=Computer, itemBoughtYear=2010]]]

In the following articles, we will discuss about YAML file to JSON and vice-versa conversions in detail

Related Articles :

References :

Happy Coding !!
Happy Learning !!

Java – How to convert YAML to JSON using ObjectMapper ?
Java – How to convert an Object to YAML using ObjectMapper ?

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