org.avaje.glue.properties.PropertiesLoader Maven / Gradle / Ivy

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package org.avaje.glue.properties;

import java.util.Enumeration;
import java.util.Properties;

/**
 * Loads and evaluates properties and yml configuration.
 */
public class PropertiesLoader {

  private static Properties properties;

  /**
   * Provides properties by reading known locations.
   * 
   * 
Main configuration
   * 
   * 
Firstly loads from main resources
   *    *   - application.properties
   *   - application.yml
   * 
   * 
   * 
Then loads from local files
   *    *   - application.properties
   *   - application.yml
   * 
   * 
   * 
Then loads from environment variable PROPS_FILE
   * Then loads from system property props.file
   * Then loads from load.properties
   * 
   * 
Test configuration
   * 
   * Once the main configuration is read it will try to read common test configuration.
   * This will only be successful if the test resources are available (i.e. running tests).
   * 
   * Loads from test resources
   *    *   - application-test.properties
   *   - application-test.yml
   * 
   */
  public static synchronized Properties load(String[] args) {

    if (properties == null) {
      Loader loader = new Loader();
      loader.load(args);
      properties = loader.eval();
    }

    return properties;
  }

  /**
   * Load the properties (if not already loaded) without using any command line args to pass properties file(s).
   */
  public static synchronized Properties load() {
    return load(null);
  }

  /**
   * Return a copy of the properties with 'eval' run on all the values.
   * This resolves expressions like ${HOME} etc.
   */
  public static Properties eval(Properties properties) {

    Properties evalCopy = new Properties();

    Enumeration names = properties.propertyNames();
    while (names.hasMoreElements()) {
      String name = (String) names.nextElement();
      String value = PropertyEval.eval(properties.getProperty(name));
      evalCopy.setProperty(name, value);
    }
    return evalCopy;
  }
}