数据库连接池详细说明

数据库连接池详细说明首先建立个池子，里面放这我们需要的链接，党我们需要链接的时候从池子里面取，取的时候先判断是否有空闲的，有就拿来用，否则检查是否全用了，如果没有全用，则新建，否则等待或者异常抛出。

假设我们要链接不同的数据库，把相关的配置写在一个xml文件，格式如下： ds.config.xml< ds-config>< pool>< type> mysql< /type>< name> test< /name>< driver> com.mysql.jdbc.driver< /driver>< url> jdbc:mysql://localhost:3306/test< /url>< username> root< /username>< password> 123456< /password>< maxconn> 100< /maxconn>< /pool>< pool>< type> mysql< /type>< name> user2< /name>< driver> com.mysql.jdbc.driver< /driver>< url> jdbc:mysql://localhost:3306/test< /url>< username> root< /username>< password> 123456< /password>< maxconn> 10< /maxconn>< /pool>< /ds-config>然后我们建立个javabean来对应这个xml，dsconfigbean.javapackage com.cgogo.dbpoolpublic class dsconfigbean {private string type = " " // 数据库类型private string name = " " // 连接池名字private string driver = " " // 数据库驱动private string url = " " // 数据库urlprivate string username = " " // 用户名private string password = " " // 密码private int maxconn = 0 // 最大连接数public dsconfigbean() {// todo auto-generated constructor stub}相关的set和get省略}接下来需要建立个池的类，来建立和释放链接dbconnectionpool.javapackage com.cgogo.dbpoolimport java.sql.connectionimport java.sql.drivermanagerimport java.sql.sqlexceptionimport java.util.arraylistimport java.util.iteratorimport java.util.timerpublic class dbconnectionpool {private connection con = nullprivate int inused = 0 // 使用的连接数private arraylist freeconnections = new arraylist() // 容器，空闲连接 private int minconn // 最小连接数private int maxconn // 最大连接private string name // 连接池名字private string password // 密码private string url // 数据库连接地址private string driver // 驱动private string user // 用户名public timer timer // 定时省略set和getpublic dbconnectionpool() {}public dbconnectionpool(string name string driver string url string user string password int maxconn) { = namethis.driver = driverthis.url = urler = userthis.password = passwordthis.maxconn = maxconn}//用完，释放连接public synchronized void freeconnection(connection con) {this.freeconnections.add(con) // 添加到空闲连接的末尾this.inused--}// timeout 根据timeout得到连接public synchronized connection getconnection(long timeout) { connection con = nullif (this.freeconnections.size() > 0) {con = (connection) this.freeconnections.get(0)if (con == null)con = getconnection(timeout) // 继续获得连接} else {con = newconnection() // 新建连接}if (this.maxconn == 0 || this.maxconn < this.inused) {con = null // 达到最大连接数，暂时不能获得连接了。

}if (con != null) {this.inused++}return con}// 从连接池里得到连接public synchronized connection getconnection() {connection con = nullif (this.freeconnections.size() > 0) {con = (connection) this.freeconnections.get(0)this.freeconnections.remove(0) // 如果连接分配出去了，就从空闲连接里删除 if (con == null)con = getconnection() // 继续获得连接} else {con = newconnection() // 新建连接}if (this.maxconn == 0 || this.maxconn < this.inused) {con = null // 等待超过最大连接时}if (con != null) {this.inused++system.out.println(" 得到" + + " 的连接，现有" + inused+ " 个连接在使用!" )}return con}// 释放全部连接public synchronized void release() {iterator allconns = this.freeconnections.iterator()while (allconns.hasnext()) {connection con = (connection) allconns.next()try {con.close()} catch (sqlexception e) {e.printstacktrace()}}this.freeconnections.clear()}//创建新连接private connection newconnection() {try {class.forname(driver)con = drivermanager.getconnection(url user password) } catch (classnotfoundexception e) {e.printstacktrace()system.out.println(" sorry can' t find db driver!" )} catch (sqlexception e1) {e1.printstacktrace()system.out.println(" sorry can' t create connection!" ) }return con}}接下来有个管理连接池的类dbconnectionmanager.javapackage com.cgogo.dbpoolimport java.sql.connectionimport java.util.enumerationimport java.util.hashtableimport java.util.iteratorimport java.util.vectorpublic class dbconnectionmanager {static private dbconnectionmanager instance // 唯一数据库连接池管理实例类static private int clients // 客户连接数private vector drivers = new vector() // 驱动信息private hashtable pools = new hashtable() // 连接池// 实例化管理类public dbconnectionmanager() {this.init()}// 得到唯一实例管理类static synchronized public dbconnectionmanager getinstance() {if (instance == null) {instance = new dbconnectionmanager()}return instance}// 释放连接public void freeconnection(string name connection con) {dbconnectionpool pool = (dbconnectionpool) pools.get(name) // 根据关键名字得到连接池if (pool != null)pool.freeconnection(con) // 释放连接}//得到一个连接根据连接池的名字namepublic connection getconnection(string name) {dbconnectionpool pool = nullconnection con = nullpool = (dbconnectionpool) pools.get(name) // 从名字中获取连接池 con = pool.getconnection() // 从选定的连接池中获得连接if (con != null)system.out.println(" 得到连接。