We now differentiate the result mapping based on projection type and query type. Previously, all projections used the domain type to map results first and then serve as backend for the projection proxy/DTO creation.
We now use direct result to DTO mapping for String-based queries to allow for a greater flexibility when declaring DTO result types. Interface-based projections and derived queries remain using the two-step process of result to domain type mapping and then mapping the domain type into the projection.
We now invoke the converter for query arguments of String-based queries (using the Query annotation or named queries) to convert the value into a type that can be used by the driver.
Previously all values were passed-thru which caused for e.g. enums to pass-thru these to the driver and the driver encode failed.
Results projected onto simple and primitive types that are null are no longer emitted.
A SQL query SELECT MAX(age) FROM my_table that returns a SQL NULL and that would be consumed as Long.class (Publisher<Long>) is an example for a primitive type that can be null. Since Reactive Streams prohibits the propagation of null values by a Publisher to a Subscriber the only viable option is to suppress null results by wrapping the mapping function into Optional result values and filter these values later to avoid null being emitted.
We now map results of exists queries to a boolean flag to ensure proper decoding. Previously, results were attempted to be mapped onto a primitive type which failed as there's no converter registered for Row to Boolean.
Mark Paluch
Greg L. Turnquist
Jens Schauder
Mark Paluch
JoseLion
Michael Simons
Christoph Strobl