Querying by example

So far, we've built up several reactive queries using property navigation. And we've updated ImageService to reactively transform our queried results into operations needed to support our social media platform.

But something that may not be apparent in the design of our data API is the fact that our method signatures are tied to the properties directly. This means that if a domain field changes, we would have to update the queries, or they will break.

There are other issues we might run into, such as offering the ability to put a filter on our web page, and letting the user fetch a subset of images based on their needs.

What if we had a system that listed information about employees. If we imagined writing a finder that lets a user enter firstName, lastName, and age range, it would probably look like this:

    interface PersonRepository 
     extends ReactiveCrudRepository<Person, Long> { 
 
       List<Person> findByFirstNameAndLastNameAndAgeBetween( 
      ...