get variables from yml file in java code,Get Variables from YAML File in Java Code: A Comprehensive Guide

Get Variables from YAML File in Java Code: A Comprehensive Guide

YAML (YAML Ain’t Markup Language) is a human-readable data serialization standard that is often used for configuration files. In Java, you might need to extract variables from a YAML file to use them in your application. This guide will walk you through the process of getting variables from a YAML file in Java code, covering various aspects such as libraries, syntax, and best practices.

Choosing the Right Library

There are several libraries available for parsing YAML files in Java. Some of the popular ones include SnakeYAML, JYAML, and YAMLBeans. For this guide, we will use SnakeYAML, as it is widely used and has good documentation.

First, you need to add the SnakeYAML library to your project. If you are using Maven, add the following dependency to your pom.xml file:

<dependency>    <groupId>org.yaml</groupId>    <artifactId>snakeyaml</artifactId>    <version>1.29</version></dependency>

For Gradle, add the following dependency to your build.gradle file:

dependencies {    implementation 'org.yaml:snakeyaml:1.29'}

Reading a YAML File

Once you have the library added to your project, you can start reading the YAML file. Here’s an example of how to read a YAML file and extract variables:

import org.yaml.snakeyaml.Yaml;import java.io.InputStream;public class YamlExample {    public static void main(String[] args) {        Yaml yaml = new Yaml();        InputStream inputStream = YamlExample.class.getClassLoader().getResourceAsStream("config.yaml");        if (inputStream == null) {            System.out.println("Sorry, unable to find config.yaml");            return;        }        Map<String, Object> data = yaml.load(inputStream);        String name = (String) data.get("name");        int age = (int) data.get("age");        System.out.println("Name: " + name);        System.out.println("Age: " + age);    }}

In this example, we are reading a YAML file named config.yaml and extracting the variables name and age. The YAML file should have the following content:

name: John Doeage: 30

Understanding YAML Syntax

YAML uses a simple and intuitive syntax for representing data. Here are some key points to keep in mind:

• Keys and Values: YAML uses keys and values to represent data. Keys are always strings, and values can be strings, numbers, lists, or nested objects.
• Lists: Lists are represented by hyphens (-) followed by the list items. For example, - item1, - item2, and - item3.
• Nested Objects: Nested objects are represented by indentation. For example:

person:  name: John Doe  age: 30  address:    street: Main St    city: Anytown

Handling Nested Objects

When dealing with nested objects, you can use the loadAs method provided by SnakeYAML to map the YAML structure to a Java object. Here’s an example:

import org.yaml.snakeyaml.Yaml;import java.io.InputStream;import java.util.Map;public class YamlExample {    public static void main(String[] args) {        Yaml yaml = new Yaml();        InputStream inputStream = YamlExample.class.getClassLoader().getResourceAsStream("config.yaml");        if (inputStream == null) {            System.out.println("Sorry, unable to find config.yaml");            return;        }        Person person = yaml.loadAs(inputStream, Person.class);        System.out.println("Name: " + person.getName());        System.out.println("Age: " + person.getAge());        System.out.println("Street: " + person.getAddress().getStreet());        System.out.println("City: " + person.getAddress().getCity());    }}class Person {    private String name;    private int age;