jooq throws NPE when fetchOne is used - mysql

Question

I have a simple query on a table which queries with the primary key.
dslContext.select(XXX.NAME)
.from(XXX)
.where(
XXX.ID.eq(id)
.and(XXX.LEVEL.eq(2))
.and(XXX.NAME.isNotNull())
)
.fetchOne().into(String.class);
In my case for a particular id, the query results in a empty set. But jooq seems to throw a NPE. When I further investigated, fetchOne() calls CursorImpl.fetchOne(). This checks the size of the result and if it is not 1, it returns null. I have a chained into(String.class) which gets called on this null value and hence resulting in NPE.
I don't want to call fetch() and iterate over the results/get the first element of the list.
Is there an alternative way of writing the query such that it will throw a org.jooq.exception.NoDataFoundException if there is no data?

Answer 1

Why a NullPointerException is being thrown
Technically, jOOQ doesn't throw a NullPointerException. Your calling into(Class) on a potentially null record does, as documented also in the Javadoc of ResultQuery.fetchOne()
Returns:
The resulting record or null if the query returns no records.
Throwing a NoDataFoundException.
You could use fetchOptional() and then use orElseThrow():
String string =
dslContext.select(XXX.NAME)
.from(XXX)
.where(
XXX.ID.eq(id)
.and(XXX.LEVEL.eq(2))
.and(XXX.NAME.isNotNull())
)
.fetchOptional()
.orElseThrow(() -> new NoDataFoundException("..."))
.into(String.class);
Note, there's a pending feature request for such a built-in fetch method: https://github.com/jOOQ/jOOQ/issues/5411
In jOOQ 3.10, you will be able to write:
String string =
dslContext.select(XXX.NAME)
.from(XXX)
.where(
XXX.ID.eq(id)
.and(XXX.LEVEL.eq(2))
.and(XXX.NAME.isNotNull())
)
.fetchSingle() // Might throw a NoDataFoundException but never returns null
.into(String.class);