Failed to instantiate [java.util.List]: Specified class is an interface in HTTP controller handler?

By Sidd Bhattacharjee -

Problem Use case:
Following SpringBoot Rest Controller is not able to map the request payload

@Controller
@RequestMapping("/api")
  public class BlogController {  
    @RequestMapping(value = "/blogstories", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)
       public ResponseEntity<List<BlogStoryObject>> addUpdateblog(List<BlogStoryObject> blogItems) {
          List<BlogStoryObject> result = new ArrayList<BlogStoryObject>();
    //TODO:: Call Service to update/save objects
    return new ResponseEntity<List<RootBlogStoryObject>>(result, HttpStatus.OK);
 }
}

Exception Details [Truncated]:

And the error thrown at runtime is Failed to instantiate [java.util.List]: Specified class is an interface.

Solution

Solution to the problem is to @RequestBody annotation to the method definition, so the following will work. 

public ResponseEntity<List<RootBlogStoryObject>> addUpdateblog(
  @RequestBody List<RootBlogStoryObject> blogItems) {
  /////implementation goes here

}

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