C3P0 在应用程序执行过程中无法建立连接答案

【问题标题】：C3P0 is not able to establish connection at middle of application executionC3P0 在应用程序执行过程中无法建立连接
【发布时间】：2014-01-15 00:05:47
【问题描述】：

在我的 Web 应用程序中，我支持 C3P0 连接池。我不断地向我的申请提出请求。在发出 10 到 12 个请求后，我的 tomcat 7 在控制台上显示异常。

    java.sql.SQLException: Connections could not be acquired from the underlying database!
        at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
        at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
        at DbConn.createConnection(DbConn.java:143)
        at DbConn.getConnection(DbConn.java:49)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
        at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:605)
        at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:544)

        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at com.github.dandelion.datatables.core.web.filter.DatatablesFilter.doFilter(DatatablesFilter.java:85)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
                at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its
        at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
        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)

我使用 C3P0 0.9.1 版本和我的 C3P0 设置如下。

    cds.setDriverClass(dbdriver);        
cds.setJdbcUrl(dburl);
cds.setUser(username);                                  
cds.setPassword(password);                                  
cds.setMinPoolSize(2);                                     
cds.setAcquireIncrement(1);
cds.setMaxPoolSize(200);
cds.setMaxStatementsPerConnection(40);
cds.setMaxConnectionAge(20);
cds.setMaxStatements(30);
cds.setIdleConnectionTestPeriod(100);
cds.setMaxConnectionAge(60);
cds.setMaxIdleTimeExcessConnections(40);

并且应用程序也停止工作。任何人都可以建议我，需要更改 C3P0 设置吗？

【问题讨论】：

整个堆栈跟踪是什么？
检查 DBA 是否限制了同时连接数
@MarkRotteveel 更新问题
您是否正在关闭从 C3P0 获得的连接以将它们返回到池中？听起来不像你。
从 JSP 调用数据库...我想说的一个不好的做法的例子。您可能想要使用一些 MVC 框架（例如 Spring），它将为您处理这些事情（JDBC 连接/事务）。

标签： java jakarta-ee jdbc c3p0

【解决方案1】：

连接完成后请关闭连接，然后只有连接返回到池中。一个建议，你现在可以转移到BoneCP它更活跃的项目，并且从生产中得到很好的反馈。 C3P0 支持不再存在。

【讨论】：