我有一个使用休眠和 OpenJPA 进行数据库连接的 Web 应用程序。但是当应用程序空闲超过 8 小时时，我在日志文件中收到以下错误。
24 Nov 2012 05:54:28 1206290820 [http-8080-20] ERROR org.hibernate.util.JDBCExce
ptionReporter - The last packet successfully received from the server was 118,4
45,988 milliseconds ago. The last packet sent successfully to the server was 11
8,445,989 milliseconds ago. is longer than the server configured value of 'wait_
timeout'. You should consider either expiring and/or testing connection validity
before use in your application, increasing the server configured values for cli
ent timeouts, or using the Connector/J connection property 'autoReconnect=true'
to avoid this problem.
24 Nov 2012 05:54:28 1206290820 [http-8080-20] DEBUG org.hibernate.ejb.AbstractE
ntityManagerImpl - mark transaction for rollback
24 Nov 2012 05:54:28 1206290820 [http-8080-20] ERROR root - org.hibernate.excep
tion.JDBCConnectionException: could not execute query
我有以下 persistence.xml 条目
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
<property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
<property name="hibernate.connection.url" value="jdbc:mysql://xxx.xxx.xxx.xxx:3306/lbs?autoReconnect=true"/>
<property name="hibernate.c3p0.min_size" value="5"/>
<property name="hibernate.c3p0.max_size" value="20"/>
<property name="hibernate.c3p0.timeout" value="1800"/>
<property name="hibernate.c3p0.max_statements" value="50"/>
<property name="hibernate.c3p0.idle_test_period" value="1800"/>
<property name="c3p0.idleConnectionTestPeriod" value="1810"/>
在其他问题之一！在 Stackoverflow 论坛上，他们说我们应该每次都关闭 EntityManager 对象。
在我的应用程序中，我正在为 EntityManager 做以下事情
我正在创建 EntityManager 作为我在整个应用程序中使用的单例类。
我错过了什么吗？
更新
c3p0 初始化的日志条目是：
INFO org.hibernate.connection.ConnectionProviderFactory - Initializing connection provider: org.hibernate.connection.C3P0ConnectionProvider
INFO org.hibernate.connection.C3P0ConnectionProvider - C3P0 using driver: com.mysql.jdbc.Driver at URL: jdbc:mysql://xxx.xxx.xxx.xxx:3306/lbs?autoReconnect=true
INFO org.hibernate.connection.C3P0ConnectionProvider - Connection properties: {user=****, password=****, autocommit=true, release_mode=auto}
INFO org.hibernate.connection.C3P0ConnectionProvider - autocommit mode: true
WARN org.hibernate.connection.C3P0ConnectionProvider - Both hibernate-style property 'hibernate.c3p0.idle_test_period' and c3p0-style property 'c3p0.idleConnectionTestPeriod' have been set in hibernate.properties. Hibernate-style property 'hibernate.c3p0.idle_test_period' will be used and c3p0-style property 'c3p0.idleConnectionTestPeriod' will be ignored!
INFO com.mchange.v2.log.MLog - MLog clients using log4j logging.
INFO com.mchange.v2.c3p0.C3P0Registry - Initializing c3p0-0.9.1 [built 16-January-2007 14:46:42; debug? true; trace: 10]
DEBUG com.mchange.v2.c3p0.management.DynamicPooledDataSourceManagerMBean - MBean: com.mchange.v2.c3p0:type=PooledDataSource[2ryrhz8rc8xlpn1l7vn76|1b15828] registered.
DEBUG com.mchange.v2.c3p0.management.DynamicPooledDataSourceManagerMBean - MBean: com.mchange.v2.c3p0:type=PooledDataSource[2ryrhz8rc8xlpn1l7vn76|1b15828] unregistered, in order to be reregistered after update.
DEBUG com.mchange.v2.c3p0.management.DynamicPooledDataSourceManagerMBean - MBean: com.mchange.v2.c3p0:type=PooledDataSource[2ryrhz8rc8xlpn1l7vn76|1b15828] registered.
INFO com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource - Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@a340a84b [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@454eed4 [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, debugUnreturnedConnectionStackTraces -> false, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 2ryrhz8rc8xlpn1l7vn76|8010fe, idleConnectionTestPeriod -> 1800, initialPoolSize -> 5, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 1800, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 20, maxStatements -> 50, maxStatementsPerConnection -> 0, minPoolSize -> 5, nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@f50d6507 [ description -> null, driverClass -> null, factoryClassLocation -> null, identityToken -> 2ryrhz8rc8xlpn1l7vn76|1233a8e, jdbcUrl -> jdbc:mysql://xxx.xxx.xxx.xxx:3306/lbs?autoReconnect=true, properties -> {user=******, password=******, autocommit=true, release_mode=auto} ], preferredTestQuery -> null, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false; userOverrides: {} ], dataSourceName -> null, factoryClassLocation -> null, identityToken -> 2ryrhz8rc8xlpn1l7vn76|1b15828, numHelperThreads -> 3 ]
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - incremented pending_acquires: 1
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - incremented pending_acquires: 2
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - incremented pending_acquires: 3
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - incremented pending_acquires: 4
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - incremented pending_acquires: 5
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - com.mchange.v2.resourcepool.BasicResourcePool@1148d7f config: [start -> 5; min -> 5; max -> 20; inc -> 3; num_acq_attempts -> 30; acq_attempt_delay -> 1000; check_idle_resources_delay -> 1800000; mox_resource_age -> 0; max_idle_time -> 1800000; excess_max_idle_time -> 0; destroy_unreturned_resc_time -> 0; expiration_enforcement_delay -> 450000; break_on_acquisition_failure -> false; debug_store_checkout_exceptions -> false]
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - acquire test -- pool size: 0; target_pool_size: 5; desired target? 1
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - awaitAvailable(): [unknown]
DEBUG com.mchange.v2.resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@1148d7f [managed: 0, unused: 0, excluded: 0]