YAML in Java: SnakeYAML and Jackson

Working with YAML in Java: SnakeYAML and Jackson Libraries

YAML (YAML Ain't Markup Language) is a human-readable data serialization format, often used for configuration files, API descriptions, and data exchange. In the Java ecosystem, there are several libraries for working with YAML, but the most popular are SnakeYAML (a low-level parser) and Jackson YAML (a high-level solution with annotation support). In this article, we will take a detailed look at both libraries, their capabilities, and usage examples.

1. SnakeYAML — The Classic YAML Parser

SnakeYAML is a simple and lightweight library that provides full control over the parsing process. It supports all YAML 1.1 specifications and allows working with both simple structures (Map, List) and custom objects.

Installing SnakeYAML

If you use Maven, add the dependency to pom.xml:

<dependency>    <groupId>org.yaml</groupId>    <artifactId>snakeyaml</artifactId>    <version>2.2</version></dependency>

For Gradle:

implementation 'org.yaml:snakeyaml:2.2'

Example: Parsing a YAML String into a Map

import org.yaml.snakeyaml.Yaml;import java.util.Map;

public class SnakeYamlExample {    public static void main(String[] args) {        String yamlString = """            server:              host: localhost              port: 8080            database:              url: jdbc:mysql://localhost:3306/mydb              user: admin              password: secret            """;

        Yaml yaml = new Yaml();        Map<String, Object> data = yaml.load(yamlString);

        System.out.println(data);        // Output: {server={host=localhost, port=8080}, database={url=jdbc:mysql://localhost:3306/mydb, user=admin, password=secret}}    }}

Example: Loading YAML from a File

import org.yaml.snakeyaml.Yaml;import java.io.FileInputStream;import java.io.InputStream;import java.util.Map;

public class SnakeYamlFileExample {    public static void main(String[] args) {        try (InputStream input = new FileInputStream("config.yaml")) {            Yaml yaml = new Yaml();            Map<String, Object> data = yaml.load(input);            System.out.println("Port: " + ((Map<String, Object>) data.get("server")).get("port"));        } catch (Exception e) {            e.printStackTrace();        }    }}

Example: Serializing a Java Object to YAML

import org.yaml.snakeyaml.Yaml;import java.util.Map;

public class SnakeYamlDumpExample {    public static void main(String[] args) {        Map<String, Object> data = Map.of(            "name", "PythonLib",            "version", 2.0,            "features", List.of("YAML", "JSON", "XML")        );

        Yaml yaml = new Yaml();        String output = yaml.dump(data);        System.out.println(output);        // Output:        // features:        // - YAML        // - JSON        // - XML        // name: PythonLib        // version: 2.0    }}

Pros of SnakeYAML:

Simple API with no extra dependencies
Support for custom types via constructors
Flexible parsing configuration (e.g., ignoring unknown fields)

2. Jackson YAML — A Modern Solution with Annotations

Jackson YAML is a module for the popular Jackson library that allows you to work with YAML just like with JSON. It supports annotations (@JsonProperty, @JsonIgnore), automatic binding to POJOs, and streaming processing.

Installing Jackson YAML

Maven:


                
    
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