anchor.diff:  
   A default lenient embedded value resolver is provided by Spring. It will try to resolve the
   property value and if it cannot be resolved, the property name (for example `${catalog.name}`)
  -will be injected as the value. If you want to maintain strict control over non existent
  +will be injected as the value. If you want to maintain strict control over nonexistent
   values, you should declare a `PropertySourcesPlaceholderConfigurer` bean, as the following
   example shows:
   
  
positive.code: 
          private final String catalog;
  
          public MovieRecommender(@Value("#{systemProperties['user.catalog'] + 'Catalog' }") String catalog){
              this.catalog = catalog;
          }
      }
  ----
  
  SpEL also enables to use more complex data structure:
  
  [source,java,indent=0]
  [subs="verbatim,quotes"]
  
negative.code: ----
  
  And the following `application.properties` file:
  
  [source,java,indent=0]
  [subs="verbatim,quotes"]
  ----
  