java的单例模式实现从配置文件获取信息和单例实现mysql的数据库连接池

java的单例模式实现从配置文件获取信息

package lm;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

public class ConfigFile {
	static public Properties p = new Properties();
	private static ConfigFile singleton = null;
	
	static public ConfigFile getInstance() {
		if (singleton == null) {
			synchronized(ConfigFile.class) {
				if (singleton == null) {
					singleton = new ConfigFile();
				}
			}
		}
		return singleton;
	}
	
	public void init(String path) throws FileNotFoundException, IOException {
		p.load(new FileInputStream(path));
	}
	
	
	public String getMysqlUrl() {
		return p.getProperty("MYSQL_URL");
	}
	public String getMYSQL_USER() {
		return p.getProperty("MYSQL_USER");
	}
	public String getMYSQL_PWD() {
		return p.getProperty("MYSQL_PWD");
	}

}

java单例实现mysql的数据库连接池

package lm;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

import up.conf.ConfigFile;

public class ConnectionPool {
	Logger LOG = LogManager.getLogger(ConnectionPool.class);
	static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
	String JDBC_DB_URL = ConfigFile.getInstance().getMysqlUrl();

	String JDBC_USER = ConfigFile.getInstance().getMYSQL_USER();
	String JDBC_PASS = ConfigFile.getInstance().getMYSQL_PWD();
	List<Connection> cs = new ArrayList<Connection>();
	private static ConnectionPool singleton = null;

	int size;
	
	static public ConnectionPool getInstance() {
		if (singleton == null) {
			synchronized(ConnectionPool.class) {
				if (singleton == null) {
					singleton = new ConnectionPool(10);
				}
			}
		}
		return singleton;
	}

	private ConnectionPool(int size) {
		this.size = size;
		init();
	}

	public void init() {
		// 这里恰恰不能使用try-with-resource的方式，因为这些连接都需要是"活"的，不要被自动关闭了
		try {
			Class.forName(JDBC_DRIVER);
			for (int i = 0; i < size; i++) {
				Connection c = DriverManager.getConnection(JDBC_DB_URL,JDBC_USER, JDBC_PASS);
				// System.out.println("完成第"+ ( i + 1 ) +"个连接");
				cs.add(c);
			}
		} catch (ClassNotFoundException e) {
			LOG.error("init connectPool: ",e);
			//System.out.println("init connectPool: " + e.getMessage());
		} catch (SQLException e) {
			LOG.error("init connectPool: ",e);
			//System.out.println("init connectPool: " + e.getMessage());
		}
	}

	public synchronized Connection getConnection() {
		while (cs.isEmpty()) {
			try {
				// 如果连接池中没有连接可用则等待
				this.wait();
			} catch (InterruptedException e) {
				//System.out.println("getConnection get error:" + e.getMessage());
				LOG.error("getConnection get error:",e);
			}
		}
		// 移除第一个连接池
		Connection conn = cs.remove(0);
		return conn;
	}

	public synchronized void returnConnection(Connection c) {
		// 使用完给回连接池中
		cs.add(c);
		// 唤醒wait告诉它有新的连接池可用
		this.notifyAll();
	}

}