Row mapping

sadu-mapper turns rows into your own classes. You register a mapper for a class once, and every query can then use mapAs(YourClass.class) instead of writing the mapping again.

sadu-queries and the database modules bring sadu-mapper with them. To add it on its own, use de.chojo.sadu:sadu-mapper:2.4.0.

Optional<User> user = Query.query("SELECT id, name FROM users WHERE id = ?")
        .single(Call.of().bind(1))
        .mapAs(User.class)
        .first();

For this to work, three things are needed:

1. A RowMapperRegistry in your query configuration. See Configuration.
2. A mapper for User in that registry, or a @MappingProvider on User. See Custom mappers.
3. The columns of the result must fit the mapper.

How SADU picks a mapper

A mapper names the columns it needs. A class can have several mappers for different column sets. For each query, SADU looks at the columns of the result and picks, among the mappers whose columns are all in the result, the one with the most columns.

A mapper without columns is a wildcard. SADU uses it when no mapper with columns fits the result. The default mappers for simple types like String or Long are wildcards.

If no mapper is registered for the class, SADU looks for a @MappingProvider on the class and registers it. If no mapper fits and there is no wildcard, mapAs throws a MappingException.

Mapper options

mapAs takes a MapperConfig as a second argument:

List<DateCount> perMonth = Query.query("SELECT month, count FROM month_stats")
        .single()
        .mapAs(DateCount.class, new MapperConfig().addAlias("time", "month"))
        .all();

Option	What it does
addAlias(original, alias)	When the mapper reads the column original, it gets the column alias instead. This way one mapper works for results with different column names.
strict()	A mapper only fits when its columns match the columns of the result exactly. Otherwise SADU uses the wildcard.

Aliases work for the getters of the Row that take a column name, also in your own mapping code.