java多线程并发之旅-22-thread pool 手写线程池

╰半橙微兮° 2022-02-25 01:20 169阅读 0赞

# 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 ##

/* * Copyright (c) 2018. houbinbin Inc. * fake All rights reserved. */
 
 package com.github.houbb.fake.dbcp;
 
 /** * * * <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 ##

/* * Copyright (c) 2018. houbinbin Inc. * fake All rights reserved. */
 
 package com.github.houbb.fake.dbcp;
 
 import java.sql.Connection;
 
 /** * * * <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 ##

import java.util.List;
 import java.util.concurrent.TimeUnit;
 
 /** * * * <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 ##

/* * Copyright (c) 2018. houbinbin Inc. * fake All rights reserved. */
 
 package com.github.houbb.fake.dbcp;
 
 /** * * * <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;
 }
 
 }

# 目录 #

[java多线程并发之旅-01-并发概览][java_-01-]

[java_-01-]: https://blog.csdn.net/ryo1060732496/article/details/88880351