jOOQ: convert Field in select statement from type1 to type2

问题

I have a statement like this:

SelectSelectStep<Record14<
    String, String, String, Timestamp, String, String, String, Integer, 
    Timestamp, String, String, String, Integer, DayToSecond>> select = create.select(
    TECHNICAL_WORK.NUMBER, TECHNICAL_CODE.CODE, TECHNICAL_CODE.DESCRIPTION,
    twLog.START_TIME, twStartLog.CODE, twStartLog.FIRST_NAME, twStartLog.LAST_NAME, twStartLog.CATEGORY,
    twLog.STOP_TIME, twEndLog.CODE, twEndLog.FIRST_NAME, twEndLog.LAST_NAME, twEndLog.CATEGORY,
    DSL.timestampDiff(twLog.STOP_TIME, twLog.START_TIME)
);

the last field is of type Field<DayToSecond> and I need to convert it to Field<Double> using DayToSecond.totalMinutes()

I can't find an api like this, eg:

DSL.timestampDiff(twLog.STOP_TIME, twLog.START_TIME).map( from -> from.totalMinutes() )

Can I do this conversion somehow?

回答1:

As you've mentioned in the comments, you cannot convert the type of a jOOQ expression by providing instructions on how to map types after fetching (although that does look interesting, I have created a feature request for this: #7100).

You have several options:

Attach a converter to your expression

This works like the feature request #7100 but is more clumsy:

Field<DayToSecond> diff = DSL.timestampDiff(
    DSL.currentTimestamp(), 
    DSL.timestamp("2018-01-01 00:00:00")
);

Field<Double> d = DSL.field("{0}", diff.getDataType()
                                       .asConvertedDataType(Converter.ofNullable(
    DayToSecond.class,
    Double.class,
    DayToSecond::getTotalMinutes,
    m -> DayToSecond.valueOf(m * 60000) // Optional implementation here
)), diff);

System.out.println(create.select(d).fetchOne());

Convert the value after fetching

Of course, you can also simply fetch a DayToSecond value and then convert the jOOQ Result using any tool of your preference, including:

Result.map(RecordMapper)
Result.stream()

来源：https://stackoverflow.com/questions/48448131/jooq-convert-field-in-select-statement-from-type1-to-type2

标签

java

sql

jooq