c3p0链接池的配置

测试了一下，支持数据库宕掉之后重启，tomcat不用重新启动，连接池会恢复链接，这点比dbcp好，下载地址
[url]
http://sourceforge.net/projects/c3p0
[/url]
配置说明如下：
<bean id="c3p0DataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
      <property name="driverClass">
        <value>${jdbc.driverClassName}</value>
      </property>
      <property name="jdbcUrl">
        <value>${jdbc.url}</value>
      </property>
      <property name="user">
       <value>${jdbc.username}</value>
      </property>
      <property name="password">
       <value>${jdbc.password}</value>
      </property>
      <property name="initialPoolSize"><value>10</value></property>
      <property name="minPoolSize"><value>5</value></property>
      <property name="maxPoolSize"><value>30</value></property>
      <property name="acquireIncrement"><value>5</value></property>
      <property name="maxIdleTime"><value>10</value></property>
      <property name="maxStatements"><value>0</value></property>
    </bean>

以下几个参数是使用的基本配置参数：
initialPoolSize：
Number of Connections a pool will try to acquire upon startup. Should be between minPoolSize and maxPoolSize
连接池初始化时获取的链接数，介于minPoolSize和maxPoolSize之间

minPoolSize：
Minimum number of Connections a pool will maintain at any given time.
最小链接数

maxPoolSize：
Maximum number of Connections a pool will maintain at any given time.
最大连接数

acquireIncrement：
Determines how many connections at a time c3p0 will try to acquire when the pool is exhausted.
在当前连接数耗尽的时候，一次获取的新的连接数

maxIdleTime：
Seconds a Connection can remain pooled but unused before being discarded. Zero means idle connections never expire.
最大空闲的时间，单位是秒，无用的链接再过时后会被回收