java 线程组作用_Java线程组（ThreadGroup）使用
JDK 對線程組類注釋：
A thread group represents a set of threads. In addition, a thread group can also include other thread groups. The thread groups form a tree in which every thread group except the initial thread group has a parent.
A thread is allowed to access information about its own thread group, but not to access information about its thread group's parent thread group or any other thread groups.
可以把線程歸屬到某一個線程組中，線程組中可以有線程對象，也可以有線程組，組中還可以有線程，這樣的組織結構有點類似于樹的形式，如圖所示.
線程組的作用是：可以批量管理線程或線程組對象，有效地對線程或線程組對象進行組織
１．線程組示例：
展示線程組結構代碼實例如下：
/**
* 類功能描述：
*
* @author WangXueXing create at 18-12-27 下午3:25
* @version 1.0.0
*/
public class ThreadGroupTest implements Runnable {
@Override
public void run() {
try {
while (!Thread.currentThread().isInterrupted()) {
Thread currentThread = Thread.currentThread();
System.out.println("current thread:" + currentThread.getName()
+" thread group:"+currentThread.getThreadGroup().getName()
+" parent thread group:"+currentThread.getThreadGroup().getParent().getName());
Thread.sleep(3000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
ThreadGroup rootThreadGroup = new ThreadGroup("root線程組1");
Thread t0 = new Thread(rootThreadGroup, new ThreadGroupTest(), "Thread 0");
t0.start();
ThreadGroup tg = new ThreadGroup(rootThreadGroup,"線程組1");
ThreadGroup tg2 = new ThreadGroup(rootThreadGroup,"線程組2");
Thread t1 = new Thread(tg, new ThreadGroupTest(), "Thread 1");
Thread t2 = new Thread(tg, new ThreadGroupTest(), "Thread 2");
t1.start();
t2.start();
Thread t3 = new Thread(tg2, new ThreadGroupTest(), "Thread 3");
Thread t4 = new Thread(tg2, new ThreadGroupTest(), "Thread 4");
t3.start();
t4.start();
}
}
打印結果如下：
current thread:Thread 0 thread group:root線程組1 parent thread group:main
current thread:Thread 2 thread group:線程組1 parent thread group:root線程組1
current thread:Thread 1 thread group:線程組1 parent thread group:root線程組1
current thread:Thread 3 thread group:線程組2 parent thread group:root線程組1
current thread:Thread 4 thread group:線程組2 parent thread group:root線程組1
current thread:Thread 1 thread group:線程組1 parent thread group:root線程組1
current thread:Thread 0 thread group:root線程組1 parent thread group:main
current thread:Thread 2 thread group:線程組1 parent thread group:root線程組1
current thread:Thread 3 thread group:線程組2 parent thread group:root線程組1
......
２．線程組項目中應用(線程組內的線程異常統一管理)：
最近有個需求，生成復雜報表－從很多表數據中分析統計到一個報表。
實現思路：
多個線程分別到不同表中查數據并統計分析，任何一個線程失敗整體報表生成失敗，記錄日志并立即中斷其他線程。全部線程成功，報表生成成功。
廢話少說以下利用Java線程組結合CountDownLatch實現代碼如下：
/**
* 多線程獲取報表數據
* @param reportId 報表ID
* @return
*/
def getReportData(reportId: Long, supplierDetailMap: ConcurrentHashMap[Integer, Supplier]):
ConcurrentHashMap[Integer, AnyRef] = {
val dataMap = new ConcurrentHashMap[Integer, AnyRef]()
//多線程同步器
val conutDownLatch = new CountDownLatch(3)
//實例化線程組
val genThreadGroup = new GenThreadGroup(request.reportInfo.reportType.name, reportId)
//獲取當月已開返利
new Thread(genThreadGroup, new Runnable {
override def run(): Unit = {
dataMap.put(OPENED_REBATE_CODE, SupplierAccountDetailQuerySql.getTaxDiscountByMonth(request))
conutDownLatch.countDown()
}
}, "獲取當月已開返利").start()
//獲取當月累計解押款
new Thread(genThreadGroup, new Runnable {
override def run(): Unit = {
dataMap.put(DEPOSIT_BY_MONTH, SupplierAccountDetailQuerySql.getDepositAmountByMonth(request))
conutDownLatch.countDown()
}
}, "獲取當月累計解押款").start()
//結算單的含稅金額
new Thread(genThreadGroup, new Runnable {
override def run(): Unit = {
dataMap.put(ACCOUNT_PAYABLE_AMOUNT, SupplierAccountDetailQuerySql.getAccountPayableAmount(request))
conutDownLatch.countDown()
}
}, "獲取結算單的含稅金額").start()
//所有線程都執行完成
conutDownLatch.await()
dataMap
}
統一捕獲異常的線程組定義如下：
/**
* 定義報表生成線程組
*
* @author BarryWang create at 2018/5/21 11:04
* @version 0.0.1
*/
class GenThreadGroup(groupName: String, reportId: Long) extends ThreadGroup(groupName){
val logger: Logger = LoggerFactory.getLogger(classOf[GenThreadGroup])
/**
* 定義線程組中任意一個線程異常處理
* @param thread 當前線程
* @param exception 異常
*/
override def uncaughtException(thread: Thread, exception: Throwable): Unit = {
logger.error(s"報表(ID：${reportId})生成異常, 線程組：${groupName}; 線程：${thread.getName} 失敗", exception)
thread.getThreadGroup.interrupt()
}
}
總結
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