为什么demo2()运行完，没有显示结果？

package com.imooc.jdbc.demo3;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import org.junit.Test;

import com.imooc.jdbc.utils.JDBCUtils;
import com.mchange.v2.c3p0.ComboPooledDataSource;

/*
 * 连接池的测试
 * @author jt
 */
public class DataSourceDemo1 {
   
	@Test
	/*
	 * 使用配置文件的方式
	 */
	public void demo2() {
		Connection conn=null;
		PreparedStatement pstmt=null;
		ResultSet rs=null;
		try {
			//获得连接
			ComboPooledDataSource dataSource=new ComboPooledDataSource();
			//获得连接
			conn=dataSource.getConnection();
			//编写SQL
			String sql="select * from user";
			//预编译SQL
			pstmt=conn.prepareStatement(sql);
		
			//设置参数
			//执行SQL
			rs=pstmt.executeQuery();
			while(rs.next()) {
				System.out.println(rs.getInt("uid")+"   "+rs.getString("username")+"   "+rs.getString("password")+"   "+rs.getString("name"));
		       }
		}catch(Exception e) {
			e.printStackTrace();
		}finally {
			JDBCUtils.release(rs, pstmt, conn);
		}
	}

报错信息

三月 09, 2019 2:31:20 下午 com.mchange.v2.log.MLog <clinit>

信息: MLog clients using java 1.4+ standard logging.

三月 09, 2019 2:31:21 下午 com.mchange.v2.c3p0.C3P0Registry banner

信息: Initializing c3p0-0.9.1.2 [built 21-May-2007 15:04:56; debug? true; trace: 10]

三月 09, 2019 2:31:21 下午 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 -> 1hge0w8a1qye500174v313|eb21112, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> null, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hge0w8a1qye500174v313|eb21112, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> null, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]

三月 09, 2019 2:31:50 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run

警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@74ea4fd2 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception:

java.sql.SQLException: No suitable driver

at java.sql.DriverManager.getDriver(DriverManager.java:315)

at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:223)

at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:119)

at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:143)

at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:132)

at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)

at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)

at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)

at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)

at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

三月 09, 2019 2:31:50 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run

警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@17715619 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: