Externalized Properties

A lightweight and extensible library to resolve application properties from various external sources.

Programming language: Java

License: Apache License 2.0

Tags: Configuration     Projects    

README

Externalized Properties

A lightweight and extensible library to resolve application properties from various external sources.

Twelve Factor Methodology

Externalized Properties was inspired by the The Twelve Factor Methodology's section III. Config.

The goal of this library is to make it easy for applications to implement configuration best practices by providing easy-to-use APIs as well as providing the flexibility to choose where to store their configurations/properties.

🛠️ Installation

Gradle

implementation "io.github.joeljeremy7.externalizedproperties:core:${version}"

Maven

<dependency>
    <groupId>io.github.joeljeremy7.externalizedproperties</groupId>
    <artifactId>core</artifactId>
    <version>${version}</version>
</dependency>

🧩 Java 9 Module Names

Externalized Properties jars are published with Automatic-Module-Name manifest attribute:

• Core - io.github.joeljeremy7.externalizedproperties.core
• Database Resolver - io.github.joeljeremy7.externalizedproperties.resolvers.database

Module authors can use above module names in their module-info.java:

module foo.bar {
    requires io.github.joeljeremy7.externalizedproperties.core;
    requires io.github.joeljeremy7.externalizedproperties.resolvers.database;
}

🌟 Features

🔗 [Property Resolution via Java Dynamic Proxies](docs/property-resolution.md) ([Why Dynamic Proxies?](docs/why-dynamic-proxies.md))

✨ Default/Fallback Values
✨ Non-static Property Names
✨ Variable Expansion
✨ Caching
✨ Eager Loading
✨ Automatic Cache Reload

🔗 [Property Post-Processing](docs/property-post-processing.md)

✨ Symmetric/Asymmetric Decryption

🔗 [Property Conversion](docs/property-conversion.md)

✨ Generic Type Conversion

🏎️ Quick Start

Given an interface:

public interface ApplicationProperties {
    @ExternalizedProperty("java.home")
    String javaHome();

    @ExternalizedProperty("encrypted.property")
    @Decrypt("MyDecryptor")
    String encryptedProperty();

    @ExternalizedProperty("java.version")
    int javaVersion();
}

We can initialize and start resolving external configurations/properties by:

public static void main(String[] args) {
    ExternalizedProperties externalizedProperties = buildExternalizedProperties();

    // Proxied interface.
    ApplicationProperties props = externalizedProperties.proxy(ApplicationProperties.class);

    // Use properties.
    String javaHome = props.javaHome();
    String encryptedProperty = props.encryptedProperty();
    int javaVersion = props.javaVersion();
}

private static ExternalizedProperties buildExternalizedProperties() {
    return ExternalizedProperties.builder()
        .withDefaults() 
        .resolvers(...)
        .processors(...)
        .converters(...) 
        .build();
}