JAVA_database.rar_SQL java_SQL java 认证_access_java sql_连接池

//package chapter5; import java.sql.*; import java.util.*; /*连接池类.能够根据要求创建新连接,直到最大连接数为止.*/ public class DBConnPool { //实际使用中的连接数 private int inUse=0; //空闲连接 private Vector connections = new Vector(); //连接池名 private String poolname; //数据库标识 private String dbid; //驱动程序名 private String drivername; //数据库账号 private String username; //数据库密码 private String passwd; //最大连接数 private int maxconn; public DBConnPool(String poolname, String drivername, String dbid, String username, String passwd, int maxconn) { this.poolname = poolname; this.dbid = dbid; this.drivername = drivername; this.username = username; this.passwd = passwd; this.maxconn = maxconn; } /*将连接返回给连接池*/ public synchronized void releaseConnection(Connection con) { // 将指定连接加入到向量末尾 connections.addElement(con); //连接数减一 inUse--; } /*从连接池得到一个连接*/ public synchronized Connection getConnection() { Connection con = null; if (connections.size() > 0) { // 获取连接列表中获得第一个连接 con = (Connection) connections.elementAt(0); connections.removeElementAt(0); //如果此连接已关闭，则继续获取 try { if (con.isClosed()) con = getConnection(); } catch (Exception ex) { ex.printStackTrace(); } } //如果实际使用的连接小于最大连接数，就新创建一个连接 else if (maxconn == 0 || inUse < maxconn) { con = newConnection(); } if (con != null) { //连接数增一 inUse++; } //返回一个连接 return con; } /*创建新的连接*/ private Connection newConnection() { Connection con = null; try { //加载驱动程序 Class.forName(drivername); //建立连接 con = DriverManager.getConnection(dbid, username, passwd); } catch (Exception e) { e.printStackTrace(); return null; } //返回该连接 return con; } /*关闭所有连接*/ public synchronized void closeConn() { Enumeration allConnections = connections.elements(); while (allConnections.hasMoreElements()) { Connection con = (Connection) allConnections.nextElement(); try { con.close(); } catch (SQLException e) { e.printStackTrace(); } } connections.removeAllElements(); } }