我正在使用Hibernate 3.3并且知道它与C3P0捆绑在一起。但是在hibernate.cfg.xml中添加了C3P0属性设置后，控制台中出现 classnotfound 异常，然后我下载并在我的类路径中添加了c3p0-0.9.1.jar，并且C3P0开始工作。
现在，当我使用Eclipse将以下行添加到我的hibernate.cfg.xml时：
<property name="hibernate.c3p0.
Intellisense只显示我：
hibernate.c3p0.acquire_increment
hibernate.c3p0.idle_test_period
hibernate.c3p0.max_size
hibernate.c3p0.max_statements
hibernate.c3p0.min_size
hibernate.c3p0.timeout
它没有向我显示 unreturnedConnectionTimeout 和 debugUnreturnedConnectionStackTraces 属性，仍然我复制粘贴这两行而没有任何效果。我没有随时在服务器日志中获得debugUnreturnedConnectionStackTraces。
下面是我的hibernate.cfg.xml：
<hibernate-configuration>
<session-factory>
<property name="hibernate.c3p0.unreturnedConnectionTimeout">40</property>
<property name="hibernate.c3p0.debugUnreturnedConnectionStackTraces">true</property>
<property name="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="hibernate.connection.url">jdbc:oracle:thin:@xyz:1521:sid</property>
<property name="hibernate.connection.username">abc</property>
<property name="hibernate.connection.password">123</property>
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">30</property>
<property name="hibernate.c3p0.timeout">20</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">3000</property>
<property name="hibernate.c3p0.unreturnedConnectionTimeout">40</property>
<property name="hibernate.c3p0.debugUnreturnedConnectionStackTraces">true</property>
</session-factory>
</hibernate-configuration>
信息级别转储为：
INFO [org.hibernate.validator.Version] (http--0.0.0.0-8081-3) Hibernate Validator 3.1.0.GA
INFO [org.hibernate.connection.ConnectionProviderFactory] (http--0.0.0.0-8081-3) Initializing connection provider: org.hibernate.connection.C3P0ConnectionProvider
INFO [org.hibernate.connection.C3P0ConnectionProvider] (http--0.0.0.0-8081-3) C3P0 using driver: oracle.jdbc.driver.OracleDriver at URL: jdbcracle:thinxyz:1521:abc
INFO [org.hibernate.connection.C3P0ConnectionProvider] (http--0.0.0.0-8081-3) Connection properties: {user=abcd, password=****, release_mode=after_statement}
INFO [org.hibernate.connection.C3P0ConnectionProvider] (http--0.0.0.0-8081-3) autocommit mode: false
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) RDBMS: Oracle, version: Oracle Database 11g Release 11.1.0.0.0 - Production
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) JDBC driver: Oracle JDBC driver, version: 10.2.0.5.0
INFO [org.hibernate.dialect.Dialect] (http--0.0.0.0-8081-3) Using dialect: org.hibernate.dialect.Oracle9Dialect
WARN [org.hibernate.dialect.Oracle9Dialect] (http--0.0.0.0-8081-3) The Oracle9Dialect dialect has been deprecated; use either Oracle9iDialect or Oracle10gDialect instead
INFO [org.hibernate.transaction.TransactionFactoryFactory] (http--0.0.0.0-8081-3) Using default transaction strategy (direct JDBC transactions)
INFO [org.hibernate.transaction.TransactionManagerLookupFactory] (http--0.0.0.0-8081-3) No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recommended)
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Automatic flush during beforeCompletion(): disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Automatic session close at end of transaction: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) JDBC batch size: 15
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) JDBC batch updates for versioned data: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Scrollable result sets: enabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) JDBC3 getGeneratedKeys(): disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Connection release mode: after_statement
WARN [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Overriding release mode as connection provider does not support 'after_statement'
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Default batch fetch size: 1
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Generate SQL with comments: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Order SQL updates by primary key: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Order SQL inserts for batching: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory
INFO [org.hibernate.hql.ast.ASTQueryTranslatorFactory] (http--0.0.0.0-8081-3) Using ASTQueryTranslatorFactory
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Query language substitutions: {}
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) JPA-QL strict compliance: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Second-level cache: enabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Query cache: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Cache region factory : org.hibernate.cache.impl.NoCachingRegionFactory
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Optimize cache for minimal puts: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Structured second-level cache entries: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Statistics: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Deleted entity synthetic identifier rollback: disabled
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Default entity-mode: pojo
INFO [org.hibernate.cfg.SettingsFactory] (http--0.0.0.0-8081-3) Named query checking : enabled
INFO [org.hibernate.impl.SessionFactoryImpl] (http--0.0.0.0-8081-3) building session factory
INFO [org.hibernate.impl.SessionFactoryObjectFactory] (http--0.0.0.0-8081-3) Not binding factory to JNDI, no JNDI name configured
com.mchange logs：
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.dialect=org.hibernate.dialect.Oracle9Dialect
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.url=jdbc:oracle:thin:@abcd:1521:xyz
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.username=yyy
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.password=xxx
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.driver_class=oracle.jdbc.driver.OracleDriver
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.provider_class=org.hibernate.connection.C3P0ConnectionProvider
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.connection.release_mode=after_statement
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.min_size=5
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.max_size=30
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.timeout=20
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.max_statements=50
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.idle_test_period=3000
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.unreturnedConnectionTimeout=40
DEBUG [org.hibernate.cfg.Configuration] (http--0.0.0.0-8081-1) hibernate.c3p0.debugUnreturnedConnectionStackTraces=true
com.mchange日志记录在ERROR级别：
ERROR [org.hibernate.util.JDBCExceptionReporter] (http--0.0.0.0-8081-1) com.mchange.v2.c3p0.PoolBackedDataSource@3a49b3d [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@f6d285eb [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, debugUnreturnedConnectionStackTraces -> true, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 31l7yg907o7aar1ysxqrk|22915056, idleConnectionTestPeriod -> 3000, initialPoolSize -> 5, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 20, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 30, maxStatements -> 50, maxStatementsPerConnection -> 0, minPoolSize -> 5, nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@8bc0578a [ description -> null, driverClass -> null, factoryClassLocation -> null, identityToken -> 31l7yg907o7aar1ysxqrk|58363f95, jdbcUrl -> jdbc:oracle:thin:@cFRO:1521:ivfrt, properties -> {user=******, password=******, release_mode=after_statement} ], preferredTestQuery -> null, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 40, usesTraditionalReflectiveProxies -> false; userOverrides: {} ], dataSourceName -> null, factoryClassLocation -> null, identityToken -> 31l7yg907o7aar1ysxqrk|301c2c35, numHelperThreads -> 3 ] has been closed() -- you can no longer use it.
TRACE [org.jboss.modules] (http--0.0.0.0-8081-8) Attempting to find resource frro/daos/administration/ in Module "deployment.appname.war:main" from Service Module Loader
ERROR [stderr] (http--0.0.0.0-8081-1) Error! Please, check your JDBC/JDNI Configurations and Database Server avaliability.
答案 0 :(得分：1)
也许新闻很好，而且您的应用程序没有连接泄漏。只有在签出Connections时，这些设置才会有效，但有时候再也不会重新检入。在一个编写良好的应用程序中永远不会发生。
尽管如此，请确认设置是“正在”。 c3p0在池初始化时将其配置转储到INFO。验证unreturnedConnectionTimeout和debugUnreturnedConnectionStackTraces是否具有您期望的值。
c3p0 0.9.1.x很老了。请至少升级到0.9.2.1或最新的0.9.5预发布版本。
如果您对调试任何连接泄漏（或没有连接泄漏）感到满意，请禁用debugUnreturnedConnectionStackTraces，这会产生显着的性能拖累。
答案 1 :(得分：0)
使用c3p0 9.2.1时，我仅在将调试级别设置为FINEST时才看到堆栈跟踪。这给出了
23/08/2019 18.32.11:BST:FINEST: com.mchange.v2.c3p0.impl.NewPooledConnection@6231dbc0 closed by a client.
java.lang.Exception: DEBUG -- CLOSE BY CLIENT STACK TRACE
at com.mchange.v2.c3p0.impl.NewPooledConnection.close(NewPooledConnection.java:646)
at com.mchange.v2.c3p0.impl.NewPooledConnection.closeMaybeCheckedOut(NewPooledConnection.java:259)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.destroyResource(C3P0PooledConnectionPool.java:619)
at com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask.run(BasicResourcePool.java:1024)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)
23/08/2019 18.32.11:BST:FINEST: com.mchange.v2.c3p0.impl.NewPooledConnection@26190855 closed by a client.
NewPooledCOnnection.java中的代码说
if (cause == null) {
this.invalidatingException = NORMAL_CLOSE_PLACEHOLDER;
if (logger.isLoggable(MLevel.FINEST)) {
logger.log(MLevel.FINEST, this + " closed by a client.", new Exception("DEBUG -- CLOSE BY CLIENT STACK TRACE"));
}
logCloseExceptions((Throwable)null, closeExceptions);
if (closeExceptions.size() > 0) {
throw new SQLException("Some resources failed to close properly while closing " + this);
}
} else {
this.invalidatingException = cause;
logCloseExceptions(cause, closeExceptions);
}
所以也许这可以解释为什么不显示堆栈跟踪。