Java实现通用线程池

线程池通俗的描述就是预先创建若干空闲线程 等到需要用多线程去处理事务的时候去唤醒某些空闲线程执行处理任务 这样就省去了频繁创建线程的时间 因为频 繁创建线程是要耗费大量的CPU资源的 如果一个应用程序需要频繁地处理大量并发事务 不断的创建销毁线程往往会大大地降低系统的效率 这时候线程池就派 上用场了

本文旨在使用Java语言编写一个通用的线程池 当需要使用线程池处理事务时 只需按照指定规范封装好事务处理对象 然后用已有的线程池对象去自动选择空 闲线程自动调用事务处理对象即可 并实现线程池的动态修改（修改当前线程数 最大线程数等） 下面是实现代码

//ThreadTask java

package polarman threadpool

/** *//**

*线程任务

* @author ryang

*

*/

public interface ThreadTask {

public void run()

}

//PooledThread java

package polarman threadpool

import java util Collectionimport java util Vector

/** *//**

*接受线程池管理的线程

* @author ryang

*

*/

public class PooledThread extends Thread {

protected Vector tasks = new Vector()

protected boolean running = false

protected boolean stopped = false

protected boolean paused = false

protected boolean killed = false

private ThreadPool pool

public PooledThread(ThreadPool pool) { this pool = pool

}

public void putTask(ThreadTask task) { tasks add(task)

}

public void putTasks(ThreadTask[] tasks) { for(int i= i<tasks lengthi++) this tasks add(tasks[i])

}

public void putTasks(Collection tasks) { this tasks addAll(tasks)

}

protected ThreadTask popTask() { if(tasks size() >) return (ThreadTask)tasks remove( )

else

return null

}

public boolean isRunning() {

return running

}

public void stopTasks() {

stopped = true

}

public void stopTasksSync() {

stopTasks()

while(isRunning()) { try {

sleep( )

} catch (InterruptedException e) {

}

}

}

public void pauseTasks() {

paused = true

}

public void pauseTasksSync() {

pauseTasks()

while(isRunning()) { try {

sleep( )

} catch (InterruptedException e) {

}

}

}

public void kill() { if(!running)

interrupt()

else

killed = true

}

public void killSync() {

kill()

while(isAlive()) { try {

sleep( )

} catch (InterruptedException e) {

}

}

}

public synchronized void startTasks() {

running = true

this notify()

}

public synchronized void run() { try { while(true) { if(!running || tasks size() == ) { pool notifyForIdleThread()//System out println(Thread currentThread() getId() + : 空闲 )this wait()}else {

ThreadTask task

while((task = popTask()) != null) { task run()if(stopped) {

stopped = false

if(tasks size() >) { tasks clear()System out println(Thread currentThread() getId() + : Tasks are stopped )

break

}

}

if(paused) {

paused = false

if(tasks size() >) { System out println(Thread currentThread() getId() + : Tasks are paused )

break

}

}

}

running = false

}

if(killed) {

killed = false

break

}

}

}catch(InterruptedException e) {

return

}

//System out println(Thread currentThread() getId() + : Killed )

}

}

//ThreadPool java

package polarman threadpool

import java util Collectionimport java util Iteratorimport java util Vector

/** *//**

*线程池

* @author ryang

*

*/

public class ThreadPool {

protected int maxPoolSize

protected int initPoolSize

protected Vector threads = new Vector()

protected boolean initialized = false

protected boolean hasIdleThread = false

public ThreadPool(int maxPoolSize int initPoolSize) { this maxPoolSize = maxPoolSizethis initPoolSize = initPoolSize

}

public void init() {

initialized = true

for(int i= i<initPoolSizei++) {

PooledThread thread = new PooledThread(this)

thread start()threads add(thread)

}

//System out println( 线程池初始化结束 线程数= + threads size() + 最大线程数= + maxPoolSize)

}

public void setMaxPoolSize(int maxPoolSize) { //System out println( 重设最大线程数 最大线程数= + maxPoolSize)this maxPoolSize = maxPoolSize

if(maxPoolSize <getPoolSize())

setPoolSize(maxPoolSize)

}

/** *//**

*重设当前线程数

* 若需杀掉某线程 线程不会立刻杀掉 而会等到线程中的事务处理完成* 但此方法会立刻从线程池中移除该线程 不会等待事务处理结束

* @param size

*/

public void setPoolSize(int size) { if(!initialized) {

initPoolSize = size

return

}else if(size >getPoolSize()) { for(int i=getPoolSize()i<size &&i<maxPoolSizei++) {

PooledThread thread = new PooledThread(this)

thread start()threads add(thread)

}

}else if(size <getPoolSize()) { while(getPoolSize() >size) { PooledThread th = (PooledThread)threads remove( )th kill()

}

}

//System out println( 重设线程数 线程数= + threads size())

}

public int getPoolSize() { return threads size()

}

protected void notifyForIdleThread() {

hasIdleThread = true

}

protected boolean waitForIdleThread() {

hasIdleThread = false

while(!hasIdleThread &&getPoolSize() >= maxPoolSize) { try { Thread sleep( )} catch (InterruptedException e) {

return false

}

}

return true

}

public synchronized PooledThread getIdleThread() { while(true) { for(Iterator itr=erator()itr hasNext()) { PooledThread th = (PooledThread)itr next()if(!th isRunning())

return th

}

if(getPoolSize() <maxPoolSize) {

PooledThread thread = new PooledThread(this)

thread start()threads add(thread)

return thread

}

//System out println( 线程池已满 等待 )

if(waitForIdleThread() == false)

return null

}

}

public void processTask(ThreadTask task) {

PooledThread th = getIdleThread()

if(th != null) { th putTask(task)th startTasks()

}

}

public void processTasksInSingleThread(ThreadTask[] tasks) {

PooledThread th = getIdleThread()

if(th != null) { th putTasks(tasks)th startTasks()

}

}

public void processTasksInSingleThread(Collection tasks) {

PooledThread th = getIdleThread()

if(th != null) { th putTasks(tasks)th startTasks()

}

}

}

下面是线程池的测试程序

//ThreadPoolTest java

import java io BufferedReaderimport java io IOExceptionimport java io InputStreamReader

import polarman threadpool ThreadPoolimport polarman threadpool ThreadTask

public class ThreadPoolTest {

public static void main(String[] args) { System out println( quit 退出 )System out println( task A 启动任务A 时长为 秒 )System out println( size 设置当前线程池大小为 )System out println( max 设置线程池最大线程数为 )System out println()

final ThreadPool pool = new ThreadPool( )pool init()

Thread cmdThread = new Thread() { public void run() {

BufferedReader reader = new BufferedReader(new InputStreamReader(System in))

while(true) { try { String line = reader readLine()String words[] = line split( )if(words[ ] equalsIgnoreCase( quit )) { System exit( )}else if(words[ ] equalsIgnoreCase( size ) &&words length >= ) { try { int size = Integer parseInt(words[ ])pool setPoolSize(size)}catch(Exception e) {

}

}else if(words[ ] equalsIgnoreCase( max ) &&words length >= ) { try { int max = Integer parseInt(words[ ])pool setMaxPoolSize(max)}catch(Exception e) {

}

}else if(words[ ] equalsIgnoreCase( task ) &&words length >= ) { try { int timelen = Integer parseInt(words[ ])SimpleTask task = new SimpleTask(words[ ] timelen * )pool processTask(task)}catch(Exception e) {

}

}

} catch (IOException e) { e printStackTrace()

}

}

}

}

cmdThread start()

/**//*

for(int i= i<i++){

SimpleTask task = new SimpleTask( Task + i (i+ )* )pool processTask(task)

}*/

}

}

class SimpleTask implements ThreadTask {

private String taskName

private int timeLen

public SimpleTask(String taskName int timeLen) { this taskName = taskNamethis timeLen = timeLen

}

public void run() { System out println(Thread currentThread() getId() +

: START TASK + taskName + )

try { Thread sleep(timeLen)} catch (InterruptedException e) {

}

System out println(Thread currentThread() getId() +

: END TASK + taskName + )

}

}

使用此线程池相当简单 下面两行代码初始化线程池

ThreadPool pool = new ThreadPool( )pool init()

要处理的任务实现ThreadTask 接口即可（如测试代码里的SimpleTask） 这个接口只有一个方法run()

两行代码即可调用

lishixinzhi/Article/program/Java/hx/201311/27203

用一个List来模拟连接池存放数据库连接，当有请求使用连接的时候就从List提出来，并list.remove(index)。当使用完之后再add回来，如果List.size为空，就new一个连接。再用一个线程来定时监控List中连接的有效性。期间要记得定义几个变量来记录数据库的连接数、“忙”连接数、空闲连接数、最大连接数、最小连接数等。至于如何建数据库连接，这个我就不说了。

我的大致思路就是这样，我也没实际动手自己写过，不知道成不成功！

DataSource ds=null

Connection con=null

PreparedStatement ps=null

ResultSet rs=null

String username=null

try{

//实现数据连接池

Context ctx=new InitialContext()

ds=(DataSource)ctx.lookup("java:comp/env/jdbc/userInfo")

}catch(NamingException ne){ne.printStackTrace()}

try{

con=ds.getConnection()

String sql="select * from guestbook order by gst_time desc"

st=con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,

ResultSet.CONCUR_READ_ONLY)

rs=st.executeQuery(sql)

。。。。。。

。。。

}

在这段代码中

Context ctx=new InitialContext()

ds=(DataSource)ctx.lookup("java:comp/env/jdbc/userInfo")就是连接池代码。

它是读取配置文件（Context.xml）中数据的。

以下是配置文件：

<Context path="/WebModule1" docBase="E:\Home\WebModule1" reloadable="true">

<Resource name="jdbc/userInfo" auth="Container" type="javax.sql.DataSource"

maxActive="100" maxIdle="30" maxWait="10000" username="sa" password="bye0406"

driverClassName="com.microsoft.jdbc.sqlserver.SQLServerDriver"

url="jdbc:microsoft:sqlserver://localhost:1433databasename=userInfo" />

</Context>

path和docBase中的路径根据自己需要配置路径。该路径是WEB应用程序的路径。driverClassName和url是连接数据库的驱动类和连接的URL，是根据你使用的哪种数据库而定。

以下是四种数据库的配制驱动：

驱动

SQL Server 2000

类名：com.microsoft.jdbc.sqlserver.SQLServerDriver

URL:jdbc:microsoft:sqlserver://localhost:1433databasename=pubs

Oracle

类名：oracle.jdbc.driver.OracleDriver

URL:jdbc:oracle:thin:@localhost:152:ORCL

Mysql

类名:com.mysql.jdbc.Driver

URL:jdbc:mysql://localhost:3306/databasename

JDBC-ODBC

类名:sun.jdbc.odbc.JdbcOdbcDriver

URL:jdbc:odbc:datasource_name

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