title: Prefix for nested configuration properties in spring
body: <p>Spring boot 2.0.0.RELEASE</p>
  
  <p>I have properties class:</p>
  
  <pre><code>@Configuration
  @ConfigurationProperties(prefix="person")
  public class PersonProperties {
  
      private AddressProperties addressProperties;
  
      public AddressProperties getAddressProperties() {
          return addressProperties;
      }
  
      public void setAddressProperties(final AddressProperties addressProperties) {
          this.addressProperties = addressProperties;
      }
  
      public static class AddressProperties {
  
          private String line1;
  
          public String getLine1() {
              return line1;
          }
  
          public void setLine1(final String line1) {
              this.line1 = line1;
          }
      }
  
  }
  </code></pre>
  
  <p>And <code>application.yml</code>:</p>
  
  <pre><code>person:
    address:
      line1: line1OfAddress
  </code></pre>
  
  <p>It is not binding properly as my <code>AddressProperties</code> object is <code>null</code>.
  When a class has the same name as yml properties <code>AddressProperties</code> -> <code>Address</code> it is working well. I tried to add <code>Qualifier</code> or <code>ConfigurationProperties</code> with a prefix <code>address</code> but it is not working. Unfortunately, I cannot find useful information about this case in spring docs.</p>
  
  <p>How to specify a prefix for nested properties? </p>