title: Spring switch implementations based on a runtime condition
body: <p>This is a simplified version of what I am trying to achieve.
  I have multiple implementations of the same interface. Based on the user input at runtime I want to pick the correct implementation. </p>
  
  <p>For example suppose I an interface called Color. There are many classes that implement this interface, the Red class, the Blue class, the Green class and so on.</p>
  
  <p>At run time I need to pick implementations based on the user input. One way to achieve this would be something like this</p>
  
  <pre><code> @Autowired
   @Qualifier("Red")
   private Color redColor;
  
   @Autowired
   @Qualifier("Green")
   private Color greenColor;
  
  
  private Color getColorImplementation()
  {
  if(userInput=="red")
  {
  return redColor;
  
  }
  else if(userInput=="green")
  {
  return greenColor;
  }
  else
  {
  return null;
  }
  
  }
  </code></pre>
  
  <p>But the problem with this is that everytime a new implementation is added, I would have to update the code that picks the implementation, which beats the whole purpose of inversion of control part of spring. What is the right way to do this using spring? </p>