block()/blockFirst()/blockLast() Are Blocking — Here's Why
WebClient.block() throws 'are blocking, which is not supported' and it looks like a Netty bug. It isn't. Here's the real mechanism, and the failure it's hiding.
IllegalStateException
6 PostsJava IllegalStateException: Duplicate Key in Collectors.toMap
Collectors.toMap throws IllegalStateException: Duplicate key when two elements map to the same key. Exact causes, JDK 8-25 message differences, and the fixes.
Kafka: Subscription to Topics, Partitions and Pattern Are Mutually Exclusive
Kafka throws IllegalStateException: Subscription to topics, partitions and pattern are mutually exclusive when you mix subscribe() and assign(). Here's the fix.
Kafka IllegalStateException: No Current Assignment for Partition
Getting java.lang.IllegalStateException: No current assignment for partition on seek()? Why Kafka's lazy assignment causes it — and the correct fix.
Kafka: Cannot Perform Operation After Producer Closed
Kafka IllegalStateException 'Cannot perform operation after producer has been closed' explained: why it happens, the Spring share
Kafka: Consumer Is Not Subscribed to Any Topics — Fix
IllegalStateException: Consumer is not subscribed to any topics or assigned any partitions — why poll() throws it, the subscribe/assign contract, and the fix.