手写线程池
本文描述了线程池的核心类。
从原理理解线程池
线程池的作用
- 降低资源消耗。
通过重复利用已创建的线程降低线程创建和销毁造成的消耗。
- 提高响应速度。
当任务到达时，任务可以不需要的等到线程创建就能立即执行。
- 提高线程的可管理性。
线程是稀缺资源，如果无限制的创建，不仅会消耗系统资源，还会降低系统的稳定性，使用线程池可以进行统一的分配，调优和监控。
代码的实现
IPool-线程池接口
[java]
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27/*
* Copyright (c) 2018. houbinbin Inc.
* fake All rights reserved.
*/
package com.github.houbb.fake.dbcp;
/**
* <p> </p>
*
* <pre> Created: 2018/8/16 下午2:13 </pre>
* <pre> Project: fake </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public interface IPool {
/**
* 获取新的数据库链接
* @return 数据库链接
*/
PoolConnection getPoolConnection();
}
PoolConnection-线程池连接对象
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53/*
* Copyright (c) 2018. houbinbin Inc.
* fake All rights reserved.
*/
package com.github.houbb.fake.dbcp;
import java.sql.Connection;
/**
* <p> </p>
*
* <pre> Created: 2018/8/16 下午2:11 </pre>
* <pre> Project: fake </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public class PoolConnection {
/**
* 是否繁忙
*/
private volatile boolean isBusy;
/**
* 数据库链接信息
*/
private Connection connection;
public PoolConnection(boolean isBusy, Connection connection) {
this.isBusy = isBusy;
this.connection = connection;
}
public boolean isBusy() {
return isBusy;
}
public void setBusy(boolean busy) {
isBusy = busy;
}
public Connection getConnection() {
return connection;
}
public void setConnection(Connection connection) {
this.connection = connection;
}
}
PoolImpl-线程池实现
[java]
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131import java.util.List;
import java.util.concurrent.TimeUnit;
/**
* <p> </p>
*
* <pre> Created: 2018/8/16 下午2:16 </pre>
* <pre> Project: fake </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public class PoolImpl implements IPool {
/**
* 数据库驱动
*/
private final String jdbcDriver;
/**
* 数据库连接
*/
private final String jdbcUrl;
/**
* 数据库用户名
*/
private final String username;
/**
* 数据库密码
*/
private final String passowrd;
/**
* 连接池大小
*/
private final int size;
/**
* 数据库连接池列表
*/
private List<PoolConnection> poolConnections = new ArrayList<>();
public PoolImpl(String jdbcDriver, String jdbcUrl, String username, String passowrd, int size) {
this.jdbcDriver = jdbcDriver;
this.jdbcUrl = jdbcUrl;
this.username = username;
this.passowrd = passowrd;
this.size = size;
init();
}
private void init() {
try {
//1. 注册数据库连接信息
Driver sqlDriver = (Driver) Class.forName(jdbcDriver).newInstance();
DriverManager.registerDriver(sqlDriver);
//2. 初始化连接池
initConnectionPool();
} catch (InstantiationException | IllegalAccessException | SQLException | ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 初始化链接
* @throws SQLException sql 异常
*/
private void initConnectionPool() throws SQLException {
for(int i = 0; i < size; i++) {
Connection connection = DriverManager.getConnection(jdbcUrl, username, passowrd);
PoolConnection poolConnection = new PoolConnection(false, connection);
poolConnections.add(poolConnection);
}
}
@Override
public PoolConnection getPoolConnection() {
if(poolConnections.size() <= 0) {
return null;
}
PoolConnection poolConnection = getRealConnection();
while (poolConnection == null) {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
poolConnection = getRealConnection();
}
return poolConnection;
}
/**
* 获取数据库链接对象
* @return 数据库链接对象
*/
private synchronized PoolConnection getRealConnection() {
for(PoolConnection poolConnection : poolConnections) {
// 寻找不处于繁忙状态的连接
if(!poolConnection.isBusy()) {
Connection connection = poolConnection.getConnection();
// 测试当前连接是否有效
try {
if(!connection.isValid(5000)) {
Connection validConnection = DriverManager.getConnection(jdbcUrl, username, passowrd);
poolConnection.setConnection(validConnection);
}
} catch (SQLException e) {
e.printStackTrace();
}
// 设置为繁忙
poolConnection.setBusy(true);
return poolConnection;
}
}
return null;
}
}
PoolManager-线程池管理类
[java]
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41/*
* Copyright (c) 2018. houbinbin Inc.
* fake All rights reserved.
*/
package com.github.houbb.fake.dbcp;
/**
* <p> </p>
*
* <pre> Created: 2018/8/16 下午2:43 </pre>
* <pre> Project: fake </pre>
*
* @author houbinbin
* @version 1.0
* @since JDK 1.7
*/
public class PoolManager {
/**
* 连接池持有类
*/
private static class PoolHolder {
private static String url = "";
private static String driver = "";
private static String username = "";
private static String password = "";
private static int size = 10;
private static IPool poolImpl = new PoolImpl(driver, url, username, password, size);
}
/**
* 内部类单利模式产生使用对象
* @return 单例
*/
public static IPool getInstance() {
return PoolHolder.poolImpl;
}
}
