数据库链接池C3P0学习

http://haoran-10.iteye.com/blog/1753332

配置文件放置：

Overriding c3p0 defaults via c3p0-config.xml

You can use the XML config file for all c3p0 configuration, including configuration of defaults, named configurations, per-user overrides, and configuration extensions.

By default, c3p0 will look for an XML configuration file in its classloader's resource path under the name "/c3p0-config.xml". That means the XML file should be placed in a directly or jar file directly named in your applications CLASSPATH, in WEB-INF/classes, or some similar location.

If you prefer not to bundle your configuration with your code, you can specify an ordinary filesystem location for c3p0's configuration file via the system property com.mchange.v2.c3p0.cfg.xml. (You can also use this property to specify an alternative location in the ClassLoader resource path, e.g. META-INF. See Locating Configuration Information.)

Here is an example c3p0-config.xml file:

<c3p0-config>
<default-config>   

    <property name="user">xxx</property>

    <property name="password">xxxxx</property>

    <property name="driverClass">oracle.jdbc.OracleDriver</property>

    <property name="jdbcUrl">jdbc:oracle:thin:@127.0.0.1:1533:xxdb</property>
    
    <property name="initialPoolSize">10</property>

    <property name="maxIdleTime">30</property>

    <property name="maxPoolSize">100</property>

    <property name="minPoolSize">10</property>

  </default-config>

  <named-config name="mySource">

    <property name="user">root</property>

    <property name="password">java</property>

    <property name="driverClass">com.mysql.jdbc.Driver</property>

    <property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbc</property>

    <property name="initialPoolSize">10</property>

    <property name="maxIdleTime">30</property>

    <property name="maxPoolSize">100</property>

    <property name="minPoolSize">10</property>

  </named-config>
  </c3p0-config>

 DataSource ds 的使用方法以下，默认根据启动配置里面可使用的链接池数目，超过配置的poolsize后，ds.getConnection()方法将等待，有释放的connection。

static DataSource ds=null;	
public static Connection getOracleConnection() {
		Connection connection=null;
		if(ds==null){
		ds=new ComboPooledDataSource();
	    }
	    try {
	    	connection=ds.getConnection();
		} 
	    catch (SQLException e) {
			e.printStackTrace();
		}
	    return connection;

	}

 

参考http://www.mchange.com/projects/c3p0/#basic_pool_configuration