Postgres閒置連接：CannotAcquireResourceException

Question

我有一個使用Hibernate 4.1.1和Spring 3.1.1和Postgres 9.2的Java/Wicket的Web應用程序。我也使用spring事務API和c3p0連接池。

我的問題是，所有可用的連接沒有發佈，以及執行所造成的GUI我得到下面的異常

com.mchange.v2.resourcepool.CannotAcquireResourceException一些select語句後：一個 ResourcePool不能從其主要工廠或 來源獲取資源。執行SELECT * FROM pg_stat_activity;表明， 有很多空閒的查詢是這樣的：SELECT NULL AS TABLE_CAT, n.nspname AS TABLE_SCHEM, c.relname AS TABLE_NAME, CASE n.nspname ~ '^pg_' OR n.nspname = 'information_schema' WHEN true THEN CASE WHEN n.nspname = 'pg_catalog' OR n.nspname = 'information_schema' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TABLE' WHEN 'v' THEN 'SYSTEM VIEW' WHEN 'i' THEN 'SYSTEM INDEX' ELSE NULL END WHEN n.nspname = 'pg_toast' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TOAST TABLE' WHEN 'i' THEN 'SYSTEM TOAST INDEX' ELSE NULL END ELSE CASE c.relkind
WHEN 'r' THEN 'TEMPORARY TABLE' WHEN 'i' THEN 'TEMPORARY INDEX'
WHEN 'S' THEN 'TEMPORARY SEQUENCE' WHEN 'v' THEN 'TEMPORARY VIEW'
ELSE NULL END END WHEN false THEN CASE c.relkind WHEN 'r' THEN 'TABLE' WHEN 'i' THEN 'INDEX' WHEN 'S' THEN 'SEQUENCE' WHEN 'v' THEN 'VIEW' WHEN 'c' THEN 'TYPE' ELSE NULL END ELSE NULL END AS TABLE_TYPE, d.description AS REMARKS FROM pg_catalog.pg_namespace n, pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_description d ON (c.oid = d.objoid AND d.ob

這是我的applicationContext.xml：

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
     xmlns:util="http://www.springframework.org/schema/util" 
     xmlns:tx="http://www.springframework.org/schema/tx" 
     xmlns:aop="http://www.springframework.org/schema/aop" 
     xmlns:lang="http://www.springframework.org/schema/lang" 
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd 
          http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd 
          http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd 
          http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd 
          http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-3.1.xsd" 
     default-autowire="byName"> 


    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" 
        destroy-method="close"> 
      <property name="driverClass" value="org.postgresql.Driver"/> 
      <property name="jdbcUrl" value="jdbc:postgresql://localhost:5432/mydatabase"/> 
      <property name="user" value="myuser"/> 
      <property name="password" value="mypassword"/> 

      <!-- configuration pool via c3p0 --> 
      <property name="initialPoolSize" value="3"/> 
      <property name="minPoolSize" value="3"/> 
      <property name="maxPoolSize" value="30"/> 
      <property name="idleConnectionTestPeriod" value="600"/> 
      <property name="maxIdleTime" value="0"/> 
      <property name="maxStatements" value="0"/> 
      <property name="maxStatementsPerConnection" value="0"/> 
      <property name="acquireIncrement" value="1"/> 
      <property name="acquireRetryAttempts" value="3"/> 
      <property name="acquireRetryDelay" value="1000"/> 
      <property name="autoCommitOnClose" value="false"/> 
      <property name="maxConnectionAge" value="14400"/> 
      <property name="forceIgnoreUnresolvedTransactions" value="false"/> 
      <property name="numHelperThreads" value="20"/> 
      <property name="testConnectionOnCheckin" value="false"/> 
      <property name="testConnectionOnCheckout" value="false"/> 
      <property name="maxAdministrativeTaskTime" value="0"/> 
      <property name="debugUnreturnedConnectionStackTraces" value="false"/> 
      <property name="maxIdleTimeExcessConnections" value="0"/> 
      <property name="breakAfterAcquireFailure" value="false"/> 
      <property name="checkoutTimeout" value="0"/> 
      <property name="unreturnedConnectionTimeout" value="0"/> 
      <property name="usesTraditionalReflectiveProxies" value="false"/> 
     </bean> 

    <bean id="exampleDao" 
     class="com.mycompany.persistence.hibernate.daoimpl.ExampleDaoImpl"> 
     <property name="sessionFactory" ref="sessionFactory" /> 
    </bean> 


    <bean id="sessionFactory" 
     class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> 
     <property name="dataSource" ref="dataSource" /> 
     <property name="annotatedClasses"> 
     <list> 
      <value>com.mycompany.model.Example</value> 
     </list> 
     </property> 

     <property name="hibernateProperties"> 
     <props> 
      <prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop> 
      <prop key="hibernate.show_sql">true</prop> 
      <prop key="hibernate.format_sql">true</prop> 
      <prop key="hibernate.current_session_context_class">org.springframework.orm.hibernate4.SpringSessionContext</prop> 
      <prop key="hibernate.auto_close_session">true</prop> 
      <prop key="hibernate.c3p0.maxSize">30</prop> 
      <prop key="hibernate.c3p0.minSize">1</prop> 
      <prop key="hibernate.c3p0.acquireIncrement">1</prop> 
      <prop key="hibernate.c3p0.idleTestPeriod">300</prop> 
      <prop key="hibernate.c3p0.timeout">1800</prop> 
      <prop key="hibernate.c3p0.maxStatements">0</prop> 
      <prop key="hibernate.c3p0.unreturnedConnectionTimeout">30</prop> 
      <prop key="hibernate.c3p0.debugUnreturnedConnectionStackTraces">true</prop> 
      <prop key="hibernate.c3p0.checkoutTimeout">0</prop> 
      <prop key="hibernate.c3p0.preferredTestQuery">SELECT * FROM dual</prop> 
     </props> 
     </property> 
    </bean> 

    <!-- Transaction Management --> 
    <tx:annotation-driven transaction-manager="transactionManager"/> 
    <bean id="transactionManager" 
    class="org.springframework.orm.hibernate4.HibernateTransactionManager"> 
     <property name="sessionFactory" ref="sessionFactory"/> 
    </bean> 
</beans> 

配置是否正確？

我的類從數據庫中檢索的數據是這樣的：

@Repository 
public class ExampleDaoImpl extends BaseDaoImpl implements ExampleDao { 
... 
    @Override 
    @Transactional(readOnly=true) 
    public List<Example> findExampleByCompanyAndType(Company company, 
      int type) { 
     return sessionFactory.getCurrentSession() 
       .createCriteria(Example.class) 
       .add(Restrictions.eq("company.companyId", 
         company.getCompanyId())) 
       .add(Restrictions.eq("type", type)).list(); 

    } 
... 
} 

Answer 1

PostgreSQL沒有實現「雙反」，所以你可能打算像選擇1有，用於測試查詢。我不知道這是否能解決您的問題，但它應該有助於集裝箱更好地管理自己。