java不使用数据库连接池会

从别处找来的。收藏了。

/** * */ package com.db; /** * @author wkupaochuan * @time Apr 11, 2012 * @version V 1.0 */ import java.sql.*; import java.util.Vector; public class Pool { private String jdbcDriver = "";//数据库驱动 private String dbUrl = "";//数据库url private String dbUsername = "";//数据库用户名 private String dbPassword = "";//数据库密码 private String testTable = ""; private int initialConnectionsNum = 10;//连接池初始连接数 private int maxConnectionsNum = 50;//连接池最大连接数 private int incrementalConnections = 5;//每次动态添加的连接数 private Vector<PooledConnection> connections = null;//向量，存放连接池中的连接，初始为空 /*无参构造函数*/ public Pool() {} /*带参数的构造函数 * 初始化数据库驱动、数据库url、数据库用户名、数据库密码、测试表 * */ public Pool(String driver, String url, String name, String pass, String table) { this.jdbcDriver = driver; this.dbUrl = url; this.dbUsername = name; this.dbPassword = pass; this.testTable = table; try { this.createPool(); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /*函数，创建连接池*/ public synchronized void createPool() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException { /*确保连接池为创建，如果已经创建，则保存连接的向量不为空 * */ if (this.connections != null) { return ; } //驱动器实例化 Driver driver = (Driver)(Class.forName(this.jdbcDriver).newInstance()); //注册驱动器 DriverManager.registerDriver(driver); //创建保存连接的向量 this.connections = new Vector<PooledConnection>(); //创建数据库连接 this.createConnections(this.initialConnectionsNum); } /*函数，创建数据库连接 * */ private void createConnections (int num) throws SQLException { /*循环创建连接 * 需要首先检查当前连接数是否已经超出连接池最大连接数 * */ for (int i = 0; i < num; ++i) { //检查 if (this.connections.size() >= this.maxConnectionsNum) { return; } //创建连接 this.connections.addElement (new PooledConnection(newConnection())); } } /*函数,创建一个数据库连接*/ private Connection newConnection() throws SQLException { /*创建连接*/ Connection con = DriverManager.getConnection(this.dbUrl, this.dbUsername, this.dbPassword); /*如果是第一次创建连接，则检查所连接的数据库的允许最大连接数是否小于 * 我们所设定的最大连接数*/ if (this.connections.size() == 0) { DatabaseMetaData metadata = con.getMetaData(); //得到数据库最大连接数 int dbMaxConnectionsNum = metadata.getMaxConnections(); //如果数据库最大连接数更小，则更改我们所设定的连接池最大连接数 if (dbMaxConnectionsNum > 0 && this.maxConnectionsNum > dbMaxConnectionsNum) { this.maxConnectionsNum = dbMaxConnectionsNum; } } return con; } /*函数，得到一个可用连接 * */ public synchronized Connection getConnection () { Connection con = null; /*检查连接池是否已经建立*/ if (this.connections == null) { return con; } //得到一个可用连接 try { con = this.getFreeConnection(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } //如果未找到合适连接，循环等待、查找，知道找到合适连接 while(con == null) { this.wait(30); try { con = this.getFreeConnection(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return con; } /*函数，得到一个可用连接*/ private Connection getFreeConnection() throws SQLException { Connection con = null; //查找一个可用连接 con = this.findFreeConnection(); //如果未找到可用连接，就建立一些新的连接，再次查找 if (con == null) { this.createConnections(this.incrementalConnections); //再次查找 con = this.findFreeConnection(); } return con; } /*函数，从现有连接中查找一个可用连接 * 在现有的连接中（向量connections中）找到一个空闲连接， * 并测试这个链接是否可用，若不可用则重新建立连接，替换原来的连接*/ private Connection findFreeConnection () throws SQLException { Connection con = null; for (int i = 0; i < this.connections.size(); ++i) { PooledConnection pol = (PooledConnection)this.connections.get(i); if (!pol.isBusy()) { /*如果此链接未被使用，则返回这个连接并，设置正在使用标志*/ con = pol.getCon(); pol.setBusy(true); /*测试连接是否可用*/ if (!this.testCon(con)) { con = this.newConnection(); pol.setCon(con); } break; } } return con; } /*函数，测试连接是否可用 * */ private boolean testCon (Connection con) { boolean useable = true; try { Statement st = con.createStatement(); ResultSet rs = st.executeQuery("select count(*) from " + this.testTable); rs.next(); } catch(SQLException e) { /*上面抛出异常，连接不可用，关闭*/ useable = false; this.closeConnection(con); } return useable; } /*函数，将使用完毕的连接放回连接池中 * */ public void returnConnection(Connection con) { /*确保连接池存在*/ if (this.connections == null) { return ; } for (int i = 0; i < this.connections.size(); ++i) { PooledConnection pool = this.connections.get(i); //找到相应连接，设置正在使用标志为false if (con == pool.getCon()) { pool.setBusy(false); } } } /*函数，刷新连接池中的连接*/ public synchronized void refreshConneciontPool () throws SQLException { /*确保连接池存在*/ if (this.connections == null) { return ; } for (int i = 0; i < this.connections.size(); ++i) { PooledConnection pool = this.connections.get(i); if (pool.isBusy()) { this.wait(5000); } this.closeConnection(pool.getCon()); pool.setCon(this.newConnection()); pool.setBusy(false); } } /*函数，关闭连接池*/ public void closeConnectionPool() { /*确保连接池存在*/ if (this.connections == null) { return ; } for (int i = 0; i < this.connections.size(); ++i) { PooledConnection pool = this.connections.get(i); if (pool.isBusy()) { this.wait(5000); } this.closeConnection(pool.getCon()); this.connections.remove(i); } this.connections = null; } /*函数，暂时无可用连接，进入等待队列等待m秒，再试 * */ private void wait(int mSecond) { try { Thread.sleep(mSecond); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * @return the jdbcDriver */ public String getJdbcDriver() { return jdbcDriver; } /** * @param jdbcDriver the jdbcDriver to set */ public void setJdbcDriver(String jdbcDriver) { this.jdbcDriver = jdbcDriver; } /** * @return the dbUrl */ public String getDbUrl() { return dbUrl; } /** * @param dbUrl the dbUrl to set */ public void setDbUrl(String dbUrl) { this.dbUrl = dbUrl; } /** * @return the dbUsername */ public String getDbUsername() { return dbUsername; } /** * @param dbUsername the dbUsername to set */ public void setDbUsername(String dbUsername) { this.dbUsername = dbUsername; } /** * @return the dbPassword */ public String getDbPassword() { return dbPassword; } /** * @param dbPassword the dbPassword to set */ public void setDbPassword(String dbPassword) { this.dbPassword = dbPassword; } /** * @return the testTable */ public String getTestTable() { return testTable; } /** * @param testTable the testTable to set */ public void setTestTable(String testTable) { this.testTable = testTable; } /** * @return the initialConnectionsNum */ public int getInitialConnectionsNum() { return initialConnectionsNum; } /** * @param initialConnectionsNum the initialConnectionsNum to set */ public void setInitialConnectionsNum(int initialConnectionsNum) { this.initialConnectionsNum = initialConnectionsNum; } /** * @return the maxConnectionsNum */ public int getMaxConnectionsNum() { return maxConnectionsNum; } /** * @param maxConnectionsNum the maxConnectionsNum to set */ public void setMaxConnectionsNum(int maxConnectionsNum) { this.maxConnectionsNum = maxConnectionsNum; } /** * @return the incrementalConnections */ public int getIncrementalConnections() { return incrementalConnections; } /** * @param incrementalConnections the incrementalConnections to set */ public void setIncrementalConnections(int incrementalConnections) { this.incrementalConnections = incrementalConnections; } /** * @return the connections */ public Vector<PooledConnection> getConnections() { return connections; } /** * @param connections the connections to set */ public void setConnections(Vector<PooledConnection> connections) { this.connections = connections; } /*函数，连接使用完毕，关闭连接*/ private void closeConnection (Connection con) { try { con.close(); } catch(SQLException e) { e.printStackTrace(); } } /*内部使用的保存数据库连接的类 * 两个成员变量：连接、是否正在使用*/ class PooledConnection { private Connection con = null;//连接 private boolean busy = false;//是否正在使用，默认为非 /*构造函数*/ public PooledConnection(Connection con) { this.con = con; } /** * @return the con */ public Connection getCon() { return con; } /** * @param con the con to set */ public void setCon(Connection con) { this.con = con; } /** * @return the busy */ public boolean isBusy() { return busy; } /** * @param busy the busy to set */ public void setBusy(boolean busy) { this.busy = busy; } } }