如何在启动时预初始化DBCP连接池？

Question

我的项目设置是 -

1. Spring JDBC用于持久化
2. Apache DBCP 1.4用于连接池
3. Linux上的Mysql 5

这是我的应用程序的日志,它捕获与数据库的交互.

2013-01-29 15:52:21,549 DEBUG http-bio-8080-exec-3 org.springframework.jdbc.core.JdbcTemplate - Executing SQL query [SELECT id from emp]
2013-01-29 15:52:21,558 DEBUG http-bio-8080-exec-3 org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource
2013-01-29 15:52:31,878  INFO http-bio-8080-exec-3 jdbc.connection - 1. Connection opened  org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
2013-01-29 15:52:31,878 DEBUG http-bio-8080-exec-3 jdbc.connection - open connections:  1 (1)
2013-01-29 15:52:31,895  INFO http-bio-8080-exec-3 jdbc.connection - 1. Connection closed  org.apache.commons.dbcp.DelegatingConnection.close(DelegatingConnection.java:247)
2013-01-29 15:52:31,895 DEBUG http-bio-8080-exec-3 jdbc.connection - open connections:  none
2013-01-29 15:52:41,950  INFO http-bio-8080-exec-3 jdbc.connection - 2. Connection opened  org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
2013-01-29 15:52:41,950 DEBUG http-bio-8080-exec-3 jdbc.connection - open connections:  2 (1)
2013-01-29 15:52:52,001  INFO http-bio-8080-exec-3 jdbc.connection - 3. Connection opened  org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
2013-01-29 15:52:52,002 DEBUG http-bio-8080-exec-3 jdbc.connection - open connections:  2 3 (2)
2013-01-29 15:53:02,058  INFO http-bio-8080-exec-3 jdbc.connection - 4. Connection opened  org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
2013-01-29 15:53:02,058 DEBUG http-bio-8080-exec-3 jdbc.connection - open connections:  2 3 4 (3)
2013-01-29 15:53:03,403 DEBUG http-bio-8080-exec-3 org.springframework.jdbc.core.BeanPropertyRowMapper - Mapping column 'id' to property 'id' of type int
2013-01-29 15:53:04,494 DEBUG http-bio-8080-exec-3 org.springframework.jdbc.datasource.DataSourceUtils - Returning JDBC Connection to DataSource

从日志中可以清楚地看到两件事 -

1. 连接池仅在收到第一个执行查询的请求时才开始创建连接.
2. 4个连接池需要将近30秒的时间进行初始化.

我的问题是 -

1. 如何配置DBCP在启动时自动初始化？
2. 创建连接真的需要很长时间吗？

注意:请不要建议切换到C3P0或Tomcat连接池.我知道那些解决方案.我更感兴趣的是了解手头的问题,而不仅仅是快速修复.此外,我确信DBCP也应该有一些基本的东西.

dbcontext的内容 -

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${db.driver}" />
    <property name="url" value="${db.jdbc.url}" />
    <property name="username" value="${db.user}" />
    <property name="password" value="${db.password}" />
    <property name="maxActive" value="20" />
    <property name="initialSize" value="4" />
    <property name="testOnBorrow" value="true" />
    <property name="validationQuery" value="SELECT 1" />
</bean>

Answer 1

在您首次请求连接之前,initialSize不会生效.从java docs到BasicDataSource #setInitialSize

设置连接池的初始大小.

注意:一旦池初始化,此方法当前不起作用.第一次调用以下方法之一时初始化池:getConnection,setLogwriter,setLoginTimeout,getLoginTimeout,getLogWriter.

尝试添加init-method="getLoginTimeout"到您的bean以确认这一点.