No, I meant on stdout. But what you posted there indicates the problem. A json codec does not keep accumulating lines until it has a complete JSON object, it parses each line as an object. What you need is a multiline code to combine all the lines for one object into a single event, then parse it using a json filter.
If you want to ingest the whole file as one event see Merge Multiline json into single line json using codec multiline plugin - #2 by Badger. If a file contains multiple objects then this might work.