PropertyDepository.java

package com.rahogata.demowebapp;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;

/**
 * Boot Application.
 */
@SpringBootApplication
@ComponentScan
public class DemoWebBootApp {
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(DemoWebBootApp.class, args);
    DemoService demoService = ctx.getBean(DemoService.class);
    demoService.dispayAppName();
  }
}

 /** This class is for accessing properties of spring configuration files
 * without injecting any Environment/@ConfigurationProperties classes.
 
 * Advantages:
 * 1. Can be used without any kind of dependecy injected in to services accessing properties.
 * 2. Avoids creation new @ConfigurationProperties annotated classes for
 *    each prefix in configuration files.
 * 3. Accessing properties in static way shortens code.
 * 4. Can hold constants having property names which could be used to obtain values with
 *    Spring provided property sources like Environment or Java System properties.
 * 
 * Disadvantages:
 * 1. Properties can not be accessed by bean configuration files during context initialization.
 * 2. During Spring context creation properties can be access if it is defined as a bean.
 */
@Component
class ConfigDepository {

  public static String APPNAME = "app.name";

  /**
   * Set all properties.
   */
  @Autowired
  public ConfigDepository(Environment env) {
    APPNAME = env.getProperty(APPNAME);
  }
}

/**
 *
 */
@Service
class DemoService {

  public void dispayAppName() {
    System.out.println(ConfigDepository.APPNAME);
  }
}