错误信息：
An attempt by a client to checkout a Connection has timed out.
java.sql.SQLException: An attempt by a client to checkout a Connection has timed out.
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
at services.callcenter.common.DBUtilHelper.searchToMap(DBUtilHelper.java:278)
at services.callcenter.test.PersonDaoImplTest.testPersonDaoImpl(PersonDaoImplTest.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at junit.framework.TestCase.runTest(TestCase.java:154)
at junit.framework.TestCase.runBare(TestCase.java:127)
at junit.framework.TestResult$1.protect(TestResult.java:106)
at junit.framework.TestResult.runProtected(TestResult.java:124)
at junit.framework.TestResult.run(TestResult.java:109)
at junit.framework.TestCase.run(TestCase.java:118)
at junit.framework.TestSuite.runTest(TestSuite.java:208)
at junit.framework.TestSuite.run(TestSuite.java:203)
at org.junit.internal.runners.OldTestClassRunner.run(OldTestClassRunner.java:35)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@4ac216 -- timeout at awaitAvailable()
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317)
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
... 22 more
问题原因：
这个问题我在google上搜索了，没有找到有具体的人给出答案。后经过我自己的测试，发现问题原因是配置出错。
是Spring中配置c3p0的时候，有一个配置属性是checkoutTimeout，把这个配置属性去掉就正常了。
源代码如下：
Spring配置文件：applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>classpath:jdbc.properties</value>
</property>
</bean>
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="oracle.jdbc.driver.OracleDriver" />
<property name="jdbcUrl" value="${jdbc.url}" />
<property name="user" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
<property name="autoCommitOnClose" value="true"/>
<property name="checkoutTimeout" value="${cpool.checkoutTimeout}"/>
<property name="initialPoolSize" value="${cpool.minPoolSize}"/>
<property name="minPoolSize" value="${cpool.minPoolSize}"/>
<property name="maxPoolSize" value="${cpool.maxPoolSize}"/>
<property name="maxIdleTime" value="${cpool.maxIdleTime}"/>
<property name="acquireIncrement" value="${cpool.acquireIncrement}"/>
<property name="maxIdleTimeExcessConnections" value="${cpool.maxIdleTimeExcessConnections}"/>
</bean>
<!-- Transaction manager for a single JDBC DataSource -->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<!-- ========================= DAO DEFINITIONS: DBUTILS IMPLEMENTATIONS ========================= -->
<bean id="dbConn" class="services.callcenter.common.DBConnection">
<property name="ds" ref="dataSource"/>
</bean>
<bean id="DBUtilHelper" class="services.callcenter.common.DBUtilHelper">
<property name="ds" ref="dataSource"></property>
</bean>
</beans>
private DataSource ds;
public void setDs(DataSource ds) {
this.ds = ds;
}
public Map searchToMap(String sql) {
Connection conn = null;
Map result = null;
QueryRunner run = new QueryRunner();
ResultSetHandler h = new MapHandler();
try {
conn = ds.getConnection();
result = (Map) run.query(conn,sql, h);
}
catch (Exception e){
log.warn(sql);
log.warn(e.getMessage(),e);
}
finally {
try{
DbUtils.close(conn);
}
catch(Exception e){
log.warn(e.getMessage(),e);
}
}
return result;
}
}
Junit测试代码如下：
package ***;
import java.util.Map;
import junit.framework.TestCase;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class PersonDaoImplTest extends TestCase{
ApplicationContext ac = null;
@Test
public void testPersonDaoImpl() throws Exception {
DBUtilHelper db=(DBUtilHelper)ac.getBean("DBUtilHelper");
String sql = "select user_id from ur_users where user_id = 371 ";
Map m = db.searchToMap(sql);
System.out.println(m.toString());
}
protected void setUp() throws Exception{
System.out.println("DDDDD");
ac=new ClassPathXmlApplicationContext("applicationContext.xml");
}
}
关于Spring代码的测试，因为Spring采用配置文件来注入某些属性，而Junit在默认的测试情况下，是不会读取这些配置文件的。所以测试Spring类的时候，需要手工指定配置文件，然后通过ClassPathXmlApplicationContext类来加载这些配置信息。
要注意把applicationContext.xml文件以及jdbc.properties文件放到src目录下。
当然，这里的测试代码只是用System.out.println直接打印出来信息，没有采用assert来判断信息，大家就别深究了！
