推荐回答（1个）
。。。，各个都系出名门，都号称具有什么什么优势，更有好事者自己开发一个连接池。那为什么要引入连接池呢？换句话说引入连接池会带来什么好处呢？下面就让我们来分析一下，探测一下谜底。[编辑]解密[编辑]数据库连接的原理
数据库连接的本底上都是tcp连接，tcp连接位于osi的4层上，所有的数据库驱动都在7层上实现自己的协议。数据库连接的协议一般都是二进制的协议。应用程序和数据库每建一个数据库其实就是在底层建立了一个tcp线路，tcp线路是有底层的操作系统实现的，每个线路占用两个端口，发送端口和接收端口，这两个端口在数据交换过程中会互换角色，时而发送、时而接收。当web应用连接mysql数据库时，目标的接收端口是3306，连接时3306要被明确的指定，此时web应用方也有一个端口被占用，这个端口不需要被明确的指定，是操作系统自动分配的。操作系统的端口数是有限的，一般缺省可能是1024，不同的操作系统会有所不同，每一个socket也是占用资源的，一般叫socket的资源描述符，这些资源对于操作系统来说也是有限的，linux下通过ulimit命令可以指定更多资源。[编辑]连接无法打开原因
占用端口不释放，每一个socket在调用close后，socket会处于Time_wait状态，处于此状态的socket需要经过一段时间才能释放，这个释放时间随不同的操作系统而不同，socket的不释放导致端口不释放，再次连接时操作系统分配不出端口
socket文件描述符不释放，还是上面的原因，socket资源不释放，操作系统不能分配新的资源[编辑]建立连接的资源开销
java的数据库连接相对来说是重量级的，构建一个连接的系统开销很大，不停的关闭、创建数据库连接对应用系统来说开销太大[编辑]连接池的应用
连接池是存储、管理数据库连接的容器，应用程序把获取数据库连接的功能委托给连接池，每个连接池都有一个上限，如果连接池达到上限，应用程序线程申请连接时被堵塞，等待其他线程释放连接，每个线程使用完连接后并不马上关闭，至少把它返还给连接池。由于连接的共享，不会频繁的创建、销毁连接，因此就不会增加创建连接的开销，也不会出现socket释放延迟现象。[编辑]其他jndi连接池是整个web容器持有，容器内所有的应用共享，有可能造成应用之间的竞争
应用级的连接池，粒度较小，容易控制
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