If the first JSON object never contains a space then the following would work. If it can contain a space I cannot think of a way of doing it except for a complicated ruby filter that takes a string containing the the two JSON objects and counts brackets to split them.
dissect { mapping => { "message" => '%{timestamp} %{host} %{appname} %{level} [%{}] [pid:%{}] [%{threadname}] %{ip} - - - %{} [%{}][%{}] %{operation} %{uri} %{}/%{} %{} %{} %{json1} %{json2}' } }
json { source => "json1" target => "first" }
json { source => "json2" target => "second" }