C3P0连接池配置

C3P0是一个开源的JDBC连接池，它实现了数据源和JNDI绑定，支持JDBC3规范和JDBC2的标准扩展。目前使用它的开源项目有Hibernate，Spring等。

闲来无事，学习了一下C3P0的配置和使用，特此把一些步骤和出现的问题记录一下：

1、JdbcUtils.java

/**
* 使用本类的方法，必须提供c3p0-copnfig.xml文件
*
* @author C
*/
public class JdbcUtils {
// 饿汉式
private static DataSource ds = new ComboPooledDataSource();
/**
* 它为null表示没有事务
* 它不为null表示有事务
* 当开启事务时，需要给它赋值
* 当结束事务时，需要给它赋值为null
* 并且在开启事务时，让dao的多个方法共享这个Connection
*/
private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
public static DataSource getDataSource() {
return ds;
}
/**
* dao使用本方法来获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
/*
* 如果有事务，返回当前事务的con 如果没有事务，通过连接池返回新的con
*/
Connection con = tl.get();// 获取当前线程的事务连接
if (con != null) {
return con;
}
return ds.getConnection();
}
/**
* 开启事务
* @throws SQLException
*/
public static void beginTransaction() throws SQLException {
Connection con = tl.get();//获取当前线程的事务连接
if (con != null) {
throw new SQLException("已经开启了事务，不能重复开启！");
}
con = ds.getConnection();//给con赋值，表示开启了事务
con.setAutoCommit(false);//设置为手动提交
tl.set(con);把当前事务连接放到tl中
}
/**
* 提交事务
* @throws SQLException
*/
public static void commitTransaction() throws SQLException {
Connection con = tl.get();//获取当前线程的事务连接
if(con == null) throw new SQLException("没有事务不能提交！");
con.commit();//提交事务
con.close();//关闭连接
con = null;//表示事务结束！
tl.remove();
}
/**
* 释放Connection
* @param con
* @throws SQLException
*/
public static void releaseConnection(Connection connection) throws SQLException {
Connection con = tl.get();//获取当前线程的事务连接
if(connection != con) {//如果参数连接，与当前事务连接不同，说明这个连接不是当前事务，可以关闭！
if(connection != null &&!connection.isClosed()) {//如果参数连接没有关闭，关闭之！
connection.close();
}
}
}
}

<?xml version="1.0" encoding="UTF-8" ?>
<c3p0-config>
<default-config>
<property name="jdbcUrl">
jdbc:mysql://localhost:3306/cms
</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="acquireIncrement">3</property>
<property name="initialPoolSize">10</property>
<property name="minPoolSize">2</property>
<property name="maxPoolSize">10</property>
</default-config>
</c3p0-config>

  c3p0.jar   mysql-connector.jar  mchange-commons-0.2.jar

问题1：如果不加入mchange-commons-0.2.jar，会出现以下问题：

     Caused by: java.lang.NoClassDefFoundError: com/mchange/v2/ser/Indirector

4、进行单元测试(导入junit4库)

JdbcUtilsTest.java

public class JdbcUtilTest {
@Test
public void jdbcUtils() throws SQLException {
Connection con = JdbcUtils.getConnection();
System.out.println(con);
}
}

2014-8-13 9:17:30 com.mchange.v2.log.MLog <clinit>
信息: MLog clients using java 1.4+ standard logging.
2014-8-13 9:17:30 com.mchange.v2.c3p0.C3P0Registry banner
信息: Initializing c3p0-0.9.2-pre1 [built 27-May-2010 01:00:49 -0400; debug? true; trace: 10]
2014-8-13 9:17:30 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1bqv9u3931kv3noythxveh|1786e64, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1bqv9u3931kv3noythxveh|1786e64, idleConnectionTestPeriod -> 0, initialPoolSize -> 10, jdbcUrl -> jdbc:mysql://localhost:3306/cms, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 10, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 2, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, statementDestroyerNumActiveThreads -> -1, statementDestroyerNumConnectionsInUseAllUsers -> -1, statementDestroyerNumConnectionsInUseDefaultUser -> -1, statementDestroyerNumConnectionsWithDeferredDestroyStatementsAllUsers -> -1, statementDestroyerNumConnectionsWithDeferredDestroyStatementsDefaultUser -> -1, statementDestroyerNumDeferredDestroyStatementsAllUsers -> -1, statementDestroyerNumDeferredDestroyStatementsDefaultUser -> -1, statementDestroyerNumIdleThreads -> -1, statementDestroyerNumTasksPending -> -1, statementDestroyerNumThreads -> -1, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
<span style="color:#ff0000;">com.mchange.v2.c3p0.impl.NewProxyConnection@1e87719</span>

方法一：修改mchange-commons-java-0.2.3.3.jar中文件，没经过深入研究，不再赘述；

方法二：和Log4j配合使用（导入log4j.jar与log4j.properties）；

log4j.properties

log4j.rootLogger=WARN,c1
log4j.appender.c1=org.apache.log4j.ConsoleAppender
log4j.appender.c1.layout=org.apache.log4j.PatternLayout
log4j.appender.c1.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} [%p] %m [%t] %c [%l]%n
#log4j.appender.f1.File=/WEB-INF/logs/file.log
#log4j.appender.f1=org.apache.log4j.DailyRollingFileAppender
#log4j.appender.f1.layout=org.apache.log4j.PatternLayout
#log4j.appender.f1.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} [%p] %m [%t] %c [%l]%n

com.mchange.v2.c3p0.impl.NewProxyConnection@c62c8

最后

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