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Later fetching
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
Using Java 8 CompletableFutures
Java 8 has introduced the new java.util.concurrent.CompletableFuture type, which allows for functional composition of asynchronous execution units. When applying this to SQL and jOOQ, you might be writing code as follows:
// Initiate an asynchronous call chain
CompletableFuture
// This lambda will supply an int value indicating the number of inserted rows
.supplyAsync(() ->
DSL.using(configuration)
.insertInto(AUTHOR, AUTHOR.ID, AUTHOR.LAST_NAME)
.values(3, "Hitchcock")
.execute()
)
// This will supply an AuthorRecord value for the newly inserted author
.handleAsync((rows, throwable) ->
DSL.using(configuration)
.fetchOne(AUTHOR, AUTHOR.ID.eq(3))
)
// This should supply an int value indicating the number of rows,
// but in fact it'll throw a constraint violation exception
.handleAsync((record, throwable) -> {
record.changed(true);
return record.insert();
})
// This will supply an int value indicating the number of deleted rows
.handleAsync((rows, throwable) ->
DSL.using(configuration)
.delete(AUTHOR)
.where(AUTHOR.ID.eq(3))
.execute()
)
.join();
The above example will execute four actions one after the other, but asynchronously in the JDK's default or common java.util.concurrent.ForkJoinPool.
For more information, please refer to the java.util.concurrent.CompletableFuture Javadoc and official documentation.
Using deprecated API
Some queries take very long to execute, yet they are not crucial for the continuation of the main program. For instance, you could be generating a complicated report in a Swing application, and while this report is being calculated in your database, you want to display a background progress bar, allowing the user to pursue some other work. This can be achived simply with jOOQ, by creating a org.jooq.FutureResult, a type that extends java.util.concurrent.Future. An example is given here:
// Spawn off this query in a separate process:
FutureResult<BookRecord> future = create.selectFrom(BOOK).where(... complex predicates ...).fetchLater();
// This example actively waits for the result to be done
while (!future.isDone()) {
progressBar.increment(1);
Thread.sleep(50);
}
// The result should be ready, now
Result<BookRecord> result = future.get();
Note, that instead of letting jOOQ spawn a new thread, you can also provide jOOQ with your own java.util.concurrent.ExecutorService:
// Spawn off this query in a separate process: ExecutorService service = // [...] FutureResult<BookRecord> future = create.selectFrom(BOOK).where(... complex predicates ...).fetchLater(service);
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