在tomcat中每一個用戶請求都是一個線程，所以可以使用線程池提高性能。
配置線程池
修改server.xm
參數說明
threadPriority （優先級）
(int) The thread priority for threads in the executor, the default is 5 (the value of theThread.NORM_PRIORITY constant)
daemon（守護進程）
(boolean) Whether the threads should be daemon threads or not, the default is true
namePrefix（名稱前綴）
(String) The name prefix for each thread created by the executor. The thread name for an individual thread will be namePrefix+threadNumber
maxThreads（最大線程數）
(int) The max number of active threads in this pool, default is 200
minSpareThreads（最小活躍線程數）
(int) The minimum number of threads always kept alive, default is 25
maxIdleTime（空閒線程等待時間）
(int) The number of milliseconds before an idle thread shutsdown, unless the number of active threads are less or equal to minSpareThreads. Default value is 60000(1 minute)
maxQueueSize（最大的等待隊裏數，超過則請求拒絕）
(int) The maximum number of runnable tasks that can queue up awaiting execution before we reject them. Default value is Integer.MAX_VALUE
prestartminSpareThreads（是否在啓動時就生成minSpareThreads個線程）
(boolean) Whether minSpareThreads should be started when starting the Executor or not, the default is false
threadRenewalDelay（重建線程的時間間隔）
(long) If a ThreadLocalLeakPreventionListener is configured, it will notify this executor about stopped contexts. After a context is stopped, threads in the pool are renewed. To avoid renewing all threads at the same time, this option sets a delay between renewal of any 2 threads. The value is in ms, default value is 1000 ms. If value is negative, threads are not renewed.
。重建線程池內的線程時，爲了避免線程同時重建，每隔threadRenewalDelay（單位： ms ）重建一個線程。默認值爲1000 ，設置爲負則不重建
配置例子
