title: SpringBoot 2 the elements were left unbound
body: <p>i have a file application.yml  with my Spring Boot application which is not willing to run.</p>
  
  <p>According to logs the reason of The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound. This property however is set in application.yml and compiler is even returning it's value.</p>
  
  <p>I'll really appreciate if someone could lend me a hand with that issue.</p>
  
  <pre><code>simulator:
      geo:
          host: http://localhost:8080/
          b12: http://localhost:8080/geo/b12
          b13: http://localhost:8080/geo/b13
          b21: http://localhost:8080/geo/b21
          c6: http://localhost:8080/geo/c6
  </code></pre>
  
  <p>and java class</p>
  
  <pre><code>@Getter
  @Configuration
  @ConfigurationProperties(prefix = "simulator",ignoreUnknownFields = false)
  public class VendorSimulatorProperties {
  
      @Value("${simulator.geo.host:http://localhost:8080/}")
      private String initUrl;
  
      @Value("${simulator.geo.b12}")
      private String geoB12Url;
  
      @Value("${simulator.geo.b13}")
      private String geoB13Url;
  
      @Value("${simulator.geo.b21}")
      private String geoB21Url;
  
      @Value("${simulator.geo.c6}")
      private String geoC6Url;
  }
  </code></pre>
  
  <p>when i start to run application, i got the error msg :</p>
  
  <pre><code>**************************
  APPLICATION FAILED TO START
  ***************************
  
  Description:
  
  Binding to target [Bindable@1c140c7c type = com.mathartsys.dlc.thirdparty.vendor.config.VendorSimulatorProperties$$EnhancerBySpringCGLIB$$eb0a550b, value = 'provided', annotations = array&lt;Annotation&gt;[@org.springframework.boot.context.properties.ConfigurationProperties(prefix=simulator, value=simulator, ignoreUnknownFields=false, ignoreInvalidFields=false)]] failed:
  
      Property: simulator.geo.b12
      Value: http://localhost:8080/geo/b12
      Origin: class path resource [config/application-dev.yml]:204:14
      Reason: The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound.
      Property: simulator.geo.b13
      Value: http://localhost:8080/geo/b13
      Origin: class path resource [config/application-dev.yml]:205:14
      Reason: The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound.
      Property: simulator.geo.b21
      Value: http://localhost:8080/geo/b21
      Origin: class path resource [config/application-dev.yml]:206:14
      Reason: The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound.
      Property: simulator.geo.c6
      Value: http://localhost:8080/geo/c6
      Origin: class path resource [config/application-dev.yml]:207:13
      Reason: The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound.
      Property: simulator.geo.host
      Value: http://localhost:8080/
      Origin: class path resource [config/application-dev.yml]:203:15
      Reason: The elements [simulator.geo.b12,simulator.geo.b13,simulator.geo.b21,simulator.geo.c6,simulator.geo.host] were left unbound.
  </code></pre>
  
  <p>this problem had confuse me long time, i hope someone can give me some advice; 
  i used springboot 2.0
  thanks </p>