YAML: Comments

Comments are used to document YAML file. Comments begin with # symbol and they can start anywhere in a line and continue till the end of the line.

employee.yml

# YAML file represent employee details
id: 1
firstName: "Krishna"
lastName: "Gurram"
address:
  city: "Bangalore"
  country: "India"
  street: "temple street"
  pinCode: "12345"

Below java application read the contents of employee.yml file and map them to an Employee instance.

Address.java

package com.sample.model;

public class Address {
 private String city;
 private String country;
 private String street;
 private String pinCode;

 public String getCity() {
  return city;
 }

 public void setCity(String city) {
  this.city = city;
 }

 public String getCountry() {
  return country;
 }

 public void setCountry(String country) {
  this.country = country;
 }

 public String getStreet() {
  return street;
 }

 public void setStreet(String street) {
  this.street = street;
 }

 public String getPinCode() {
  return pinCode;
 }

 public void setPinCode(String pinCode) {
  this.pinCode = pinCode;
 }

 @Override
 public String toString() {
  return "Address [city=" + city + ", country=" + country + ", street=" + street + ", pinCode=" + pinCode + "]";
 }

}

Employee.java

package com.sample.model;

public class Employee {

 private int id;
 private String firstName;
 private String lastName;
 private Address address;

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 public Address getAddress() {
  return address;
 }

 public void setAddress(Address address) {
  this.address = address;
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", address=" + address
    + "]";
 }

}

YAMLUtil.java

package com.sample.util;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;

public class YAMLUtil {

 private static ObjectMapper mapper = new ObjectMapper(new YAMLFactory());

 public static void printYAML(Object obj) throws JsonGenerationException, JsonMappingException, IOException {
  mapper.writeValue(System.out, obj);
 }

 public static <T> T getObject(String yaml, Class<T> clazz)
   throws JsonParseException, JsonMappingException, IOException {
  return mapper.readValue(yaml, clazz);

 }
}

Test.java

package com.sample.app;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.sample.model.Employee;
import com.sample.util.YAMLUtil;

public class Test {

 private static final String filePath = "C:\\Users\\krishna\\Documents\\Study\\YAML\\yaml files\\employee.yml";

 public static void main(String args[]) throws JsonGenerationException, JsonMappingException, IOException {

  String fileString = new String(Files.readAllBytes(Paths.get(filePath)), StandardCharsets.UTF_8);

  Employee emp = YAMLUtil.getObject(fileString, Employee.class);

  System.out.println(emp);
 }
}

Output

Employee [id=1, firstName=Krishna, lastName=Gurram, address=Address [city=Bangalore, country=India, street=temple street, pinCode=12345]]

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