How to Write a Quick and Dirty Converter in jOOQ

In jOOQ 3.9+, this is a no-brainer, as we’ve finally introduced the <javaTimeTypes> flag to automatically generate JSR 310 types instead of JDBC types. But sometimes you want some custom conversion behavior, so you write a Converter.

To the rescue are our new jOOQ 3.9+ converter constructors, which essentially take two lambdas to construct a converter for you. For instance:

Converter<Timestamp, LocalDateTime> converter =
Converter.of(
    Timestamp.class,
    LocalDateTime.class,
    t -> t == null ? null : t.toLocalDateTime(),
    u -> u == null ? null : Timestamp.valueOf(u)
);

And you’re set! Even easier, if you don’t need any special null encoding (as above), just write this equivalent converter, instead:

Converter<Timestamp, LocalDateTime> converter =
Converter.ofNullable(
    Timestamp.class,
    LocalDateTime.class,
    Timestamp::toLocalDateTime
    Timestamp::valueOf
);

Where’s that useful? The code generator needs a concrete converter class, so you cannot use that with the code generator, but there are many other places in the jOOQ API where converters are useful, including when you write plain SQL like this:

DSL.field(
    "my_table.my_timestamp",
    SQLDataType.TIMESTAMP.asConvertedDataType(
        Converter.ofNullable(...)
));