资源池模式和单例模式实现的自定义数据库连接池java实现版

在企业级开发中，我们往往不会直接使用原生的JDBC操作来实现与数据库得连接。因为数据库的连接是一个很宝贵的资源且耗时，我们往往会在内存中引入一个资源池来统一管理数据库的连接。这个模式也被总结为一种设计模式：资源池模式和单例模式。

关于原理部分就不多做介绍了，这里也是做一个简单的原理实现。

ObjectPool连接池接口

package com.test.pool;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.concurrent.ConcurrentHashMap;

public abstract class ObjectPool<T> {
	  private long expirationTime;

	  private Hashtable<T, Long> locked, unlocked;

	  public ObjectPool() {
	    expirationTime = 30000; // 30 seconds
	    locked = new Hashtable<T, Long>();
	    unlocked = new Hashtable<T, Long>();
	  }

	  protected abstract T create();

	  public abstract boolean validate(T o);

	  public abstract void expire(T o);

	  public synchronized T checkOut() {
	    long now = System.currentTimeMillis();
	    T t;
	    if (unlocked.size() > 0) {
	      Enumeration<T> e = unlocked.keys();
	      while (e.hasMoreElements()) {
	        t = e.nextElement();
	        if ((now - unlocked.get(t)) > expirationTime) {
	          // object has expired
	          unlocked.remove(t);
	          expire(t);
	          t = null;
	        } else {
	          if (validate(t)) {
	            unlocked.remove(t);
	            locked.put(t, now);
	            return (t);
	          } else {
	            // object failed validation
	            unlocked.remove(t);
	            expire(t);
	            t = null;
	          }
	        }
	      }
	    }
	    // no objects available, create a new one
	    t = create();
	    locked.put(t, now);
	    return (t);
	  }

	  public synchronized void checkIn(T t) {
	    locked.remove(t);
	    unlocked.put(t, System.currentTimeMillis());
	  }
}

JDBCConnectionPool 连接池实现

package com.test.pool;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class JDBCConnectionPool extends ObjectPool<Connection> {

	  private String driver, url, username, password;

	  private JDBCConnectionPool() {

	  }

	  private static volatile JDBCConnectionPool instance;

	  public static JDBCConnectionPool getInstance() {
		  if(instance == null) {
			  synchronized (JDBCConnectionPool.class) {
				  if(instance == null) {
					  instance = new JDBCConnectionPool();
				  }
			  }
		  }
		  return instance;
	  }

	  @Override
	  protected Connection create() {
	    try {
	      return (DriverManager.getConnection(url, username, password));
	    } catch (SQLException e) {
	      e.printStackTrace();
	      return (null);
	    }
	  }

	  @Override
	  public void expire(Connection o) {
	    try {
	      ((Connection) o).close();
	    } catch (SQLException e) {
	      e.printStackTrace();
	    }
	  }

	  @Override
	  public boolean validate(Connection o) {
	    try {
	      return (!((Connection) o).isClosed());
	    } catch (SQLException e) {
	      e.printStackTrace();
	      return (false);
	    }
	  }

	public String getDsn() {
		return url;
	}

	public void setDsn(String dsn) {
		this.url = dsn;
	}

	public String getUsr() {
		return username;
	}

	public void setUsr(String usr) {
		this.username = usr;
	}

	public String getPwd() {
		return password;
	}

	public void setPwd(String pwd) {
		this.password = pwd;
	}

	public String getDriver() {
		return driver;
	}

	public void setDriver(String driver) {
		this.driver = driver;
	}

	public void loadDriver() {
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
		}
	}

}

Main测试

package com.test.pool;

import java.sql.Connection;
import java.sql.SQLException;

public class Main {
	  public static void main(String args[]) throws SQLException {

	    JDBCConnectionPool pool = JDBCConnectionPool.getInstance();
	    pool.setDriver("com.mysql.jdbc.Driver");
	    pool.setDsn("jdbc:mysql://192.168.2.113:3306/jhbims?useSSL=false&useUnicode=true&characterEncoding=UTF-8&autoReconnect=true");
	    pool.setUsr("jhbims");
	    pool.setPwd("jhbims");
	    pool.loadDriver();

	    // Get a connection:
	    Connection con = pool.checkOut();
	    System.out.println(con.isValid(0));

	    pool.checkIn(con);

	  }
	}

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