ConfigurationProperties binding a property name with a number in from a yaml file

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06-10-2024

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ConfigurationProperties: Binding Properties with Numbers in Your YAML Files

Spring Boot's @ConfigurationProperties annotation simplifies configuration management, allowing you to map properties from external sources (like YAML files) directly to Java objects. However, you might encounter a hurdle when dealing with property names containing numbers. Let's dive into this common scenario and explore how to navigate it effectively.

The Problem:

Imagine you have a YAML configuration file containing properties with numerical identifiers, like:

my.config.property1: "value1"
my.config.property2: "value2"

You might want to bind these properties to a Java class using @ConfigurationProperties. However, the conventional way of using @ConfigurationProperties("my.config") would only bind properties that match the specified prefix exactly. This leaves properties like my.config.property2 unbound.

The Solution:

Spring Boot provides a powerful solution to this through nested configuration. By defining nested classes within your configuration class, you can elegantly handle properties with numerical identifiers. Let's see how this works in practice:

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties("my.config")
public class MyConfig {

    private Property1 property1;
    private Property2 property2;

    public Property1 getProperty1() {
        return property1;
    }

    public void setProperty1(Property1 property1) {
        this.property1 = property1;
    }

    public Property2 getProperty2() {
        return property2;
    }

    public void setProperty2(Property2 property2) {
        this.property2 = property2;
    }

    @ConfigurationProperties("property1")
    public static class Property1 {
        private String value;

        public String getValue() {
            return value;
        }

        public void setValue(String value) {
            this.value = value;
        }
    }

    @ConfigurationProperties("property2")
    public static class Property2 {
        private String value;

        public String getValue() {
            return value;
        }

        public void setValue(String value) {
            this.value = value;
        }
    }
}

In this example:

1. MyConfig is annotated with @ConfigurationProperties("my.config"), indicating that it should bind properties starting with this prefix.
2. Property1 and Property2 are nested classes within MyConfig. These classes represent individual properties, and each is annotated with @ConfigurationProperties to bind specific properties: "property1" and "property2," respectively.

This setup allows Spring Boot to correctly map the values from your YAML file to the corresponding properties within the nested classes.

Additional Insights:

• Flexibility: This approach offers flexibility. You can use nested classes to represent complex configurations with hierarchical structures.
• Code Clarity: It enhances the readability and organization of your configuration code.

Remember:

• Ensure your YAML file is well-formatted and follows standard conventions.
• Use a consistent naming scheme for your properties.
• Consider using IDE support for auto-completion and validation during development.

In Conclusion:

Handling property names with numbers in YAML files with @ConfigurationProperties requires a slight change in your configuration strategy. By leveraging nested classes, you can achieve a seamless mapping of values to your Java objects, promoting maintainable and robust configurations.