spring - SimpleMessageListenerContainer and TaskExecutor always only 1 message processed -

i have simplemessagelistenercontainer using taskexecutor (pool size = 15) never process more 1 message @ time. here how configured.

simplemessagelistenercontainer settings are:

concurrentconsumers = 1 (e.g., 1 jms consumer) taskexecutor = instance of java.util.concurrent.threadpoolexecutor 

threadpoolexecutor settings are:

corepoolsize = 1 maximumpoolsize= 15 workqueue = linkedblockingqueue<runnable> size 200 

my expectation:

i expect 1 jms consumer pull off messages , run them fast possible in 1 of background taskexecutor threads. if 50 messages on queue, pull off 50. run 15 @ time while other 35 held in taskexecutor's linkedblockingqueue internal queue.

what's happening:

instead, app processes 1 message @ time. in jconsole, have extended container , exposed more jmx attributes task executor status, see "taskexecutor" activecount 1 maximum (e.g. threadpoolexecutor.getactivecount()). threadpoolexecutor never moves 15. so, jms consumer still processing 1 message @ time taskexecutor thread pool of 15 processing messages.

here's jconsole jmx readings show after flooded queue tons of messages.

• concurrentconsumers = maps spring's simplemessagecontainer.concurrentconsumers

• activecount = maps threadpoolexecutor.activecount

• minconcurrentconsumers = maps threadpoolexecutor.corepoolsize
• maxconcurrentconsumers = maps threadpoolexecutor.maximumpoolsize
• internalqueuecapacity = maps threadpoolexecutor's linkedblockingqueue size.

what missing? need use different implementation of executor?

i found link helpful in resolving issue:

how configure threadpoolexecutor grow/shrink

my corepoolsize 1 , internally, threadpoolexecutor queued messages , processed queued messages single core thread. setting corepoolsize higher allowed growth of # of threads wanted.