title: How to bind a yml map to a Java map in spring-boot configuration?
body: <p>I am trying to follow this guide here: </p>
  
  <p><a href="https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-Configuration-Binding" rel="nofollow noreferrer">https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-Configuration-Binding</a></p>
  
  <p>but I am struggling to get it to work.</p>
  
  <p>I want to initialize a HashMap from a map defined in application.yml.</p>
  
  <p>This is my last try at the yml-map definition:</p>
  
  <pre><code>symbols:
      symbolPairs.CombinationsAlpha="CombinationsAlpha"
      symbolPairs.[CombinationsAlpha]=aaabbb, bbbaaa, ccceee, dddggg
      symbolPairs.Combinations="CombinationsInteger"
      symbolPairs.[CombinationsAlpha]=000111, 222666, 999000, 151515
  </code></pre>
  
  <p>And this is my java class:</p>
  
  <pre><code>@Data
  @Configuration
  @EnableConfigurationProperties
  @ConfigurationProperties(prefix = "symbols")
  public class SymbolsConfig {
    private Map&lt;String, List&lt;String&gt;&gt; symbolPairs = new HashMap&lt;&gt;();
  }
  </code></pre>
  
  <p>I want to have <code>"CombinationsAplha"</code> and <code>"CombinationsInteger"</code>injected as keys and the values as a List of Strings.
  I am struggling to define the yml correctly.</p>
  
  <p>The <code>@Data</code> annotation from <a href="https://projectlombok.org/" rel="nofollow noreferrer">projectlombok</a> generates getters and setters.</p>