我有一个使用Hibernate（打开和关闭会话）的应用程序，但是有人建议我使用C3P0。我在互联网上搜索时发现，只有这些行，所有应用程序都应该像以前一样工作，而不是更改它，但应使用“ Conconction pool”。
<property name="connection.provider_class">
org.hibernate.connection.C3P0ConnectionProvider
</property>
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">60</property> <!-- seconds -->
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">10</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.timeout">0</property> <!-- seconds -->
<property name="hibernate.c3p0.acquireRetryAttempts">1</property>
<property name="hibernate.c3p0.acquireRetryDelay">250</property>
但是我的问题是，当我将其添加到hibernate.cfg.xml中时。我不知道为什么，但是当应用程序到达此行时：
SessionFactory sessionFactory = SessionFactoryUtil.getSessionFactory();
引发此异常：
Initial SessionFactory creation failed.org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.service.jdbc.connections.spi.ConnectionProvider]
sep 22, 2018 4:34:48 PM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: El Servlet.service() para el servlet [Servlets.Login] en el contexto con ruta [/Just4Goals] lanzó la excepción [La ejecución del Servlet lanzó una excepción] con causa raíz
java.lang.ClassNotFoundException: Could not load requested class : org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider
at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl$1.findClass(ClassLoaderServiceImpl.java:99)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:138)
at org.hibernate.service.jdbc.connections.internal.ConnectionProviderInitiator.instantiateExplicitConnectionProvider(ConnectionProviderInitiator.java:189)
at org.hibernate.service.jdbc.connections.internal.ConnectionProviderInitiator.initiateService(ConnectionProviderInitiator.java:114)
at org.hibernate.service.jdbc.connections.internal.ConnectionProviderInitiator.initiateService(ConnectionProviderInitiator.java:54)
at org.hibernate.service.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:69)
at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:177)
at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:150)
at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:223)
at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:89)
at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:71)
at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2273)
at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2269)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1738)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1778)
at tratadoDatosBD.SessionFactoryUtil.<clinit>(SessionFactoryUtil.java:72)
at usersLogin.EncryptData.comprobarLogin(EncryptData.java:146)
at Servlets.Login.Checklogin(Login.java:83)
at Servlets.Login.doPost(Login.java:39)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:407)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
但是当我不向hibernate.cfg.xml中添加C3P0属性时，该应用程序就可以正常工作。
我应该添加更多内容吗？我应该更改代码以使连接池起作用吗？为什么这不起作用？
谢谢！