今日总结

2020年11月17日：

ConnectionPool .java

package com.enfo.wd;
import java.sql.Connection;
import java.util.LinkedList;
public class ConnectionPool 
    private LinkedList<Connection> pool=new LinkedList<Connection>();
    public ConnectionPool(int initialSize){
        if(initialSize>0){
            for(int i=0;i<initialSize;i++){
                pool.addLast(ConnectionDriver.createConnection());
            }
        }
    }
    public void releaseConnection(Connection connection){
        if(connection!=null){
            synchronized (pool) {
                //连接释放后需要进行通知，这样其他消费者能够感知到连接池中已经归还了一个连接
                pool.addLast(connection);
                pool.notifyAll();
            }
        }
    }
    //在mills内无法获取到连接，将会返回null
    public Connection fetchConnection(long mills)throws Exception{
        //完全超时
        if(mills<=0){
            while(pool.isEmpty()){
                pool.wait();
            }
            return pool.removeFirst();
        }else{
            long future=System.currentTimeMillis()+mills;
            long remaining=mills;
            while(pool.isEmpty()&&remaining>0){
                pool.wait(remaining);
                remaining=future-System.currentTimeMillis();
            }
            Connection result=null;
            if(!pool.isEmpty()){
                result=pool.removeFirst();
            }
            return result;
        }

    }
}

ConnectionDriver .java

package com.enfo.wd;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.util.concurrent.TimeUnit;
public class ConnectionDriver {
    static class ConnectionHandler implements InvocationHandler{
        public Object invoke(Object proxy,Method method,Object[] args) throws Throwable{
            if(method.getName().equals("commit")){
                TimeUnit.MILLISECONDS.sleep(100);
            }
            return null;
        }
    }
    //创建一个connection的代理，在commit时休眠100毫秒
    public static final Connection createConnection() {
        return (Connection) Proxy.newProxyInstance(ConnectionDriver.class.getClassLoader(), new Class<?>[]{Connection.class},new ConnectionHandler());
    }
}

ConnectionTest .java

package com.enfo.wd;

import java.sql.Connection;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

public class ConnectionTest {
    static ConnectionPool pool=new ConnectionPool(10);
    //保证所有的ConnetionRunner 能够同时开始
    static CountDownLatch start=new CountDownLatch(1);
    //mine线程将会等待 所有的ConnetionRunner 结束后才能继续执行
    static CountDownLatch end;
    public static void main(String[] args) throws Exception{
        //通过修改线程数据量，观察数据变化
        int threadCount=10;
        end=new CountDownLatch(threadCount);
        int count=20;
        AtomicInteger got=new AtomicInteger();
        AtomicInteger notGot=new AtomicInteger();
        for(int i=0;i<threadCount;i++){
            Thread thread=new Thread(new ConnetionRunner(count,got,notGot),"ConnectionRunnerThread");
            thread.start();
        }
        start.countDown();
        end.await();
        System.out.println("total invoke:"+(threadCount*count));
        System.out.println("got connection:"+got);
        System.out.println("not got connection:"+notGot);
    }

    static class ConnetionRunner implements Runnable{
        int count;
        AtomicInteger got;
        AtomicInteger notGot;

        public ConnetionRunner(int count,AtomicInteger got,AtomicInteger notGot){
            this.count=count;
            this.got=got;
            this.notGot=notGot;
        }
        public void run() {
            try {
                start.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            while (count>0) {
                try {
                    Connection connection=(Connection) pool.fetchConnection(1000);
                    if(connection!=null){
                        try {
                            //从线程池中获取连接，如果1000ms内无法获取到，将返回null
                            //分别统计连接获取的数量got 和未获取到的数量notGot
                            connection.createStatement();
                            connection.commit();
                        } finally {
                            pool.releaseConnection(connection);
                            got.incrementAndGet();
                        }
                    }else{
                        notGot.incrementAndGet();
                    }
                } catch (Exception e) {

                }finally{
                    count--;
                }

            }
            end.countDown();
        }
    }

}