休眠/ mysql連接問題

Question

我們正在研究一個帶有Hibernate 3 ORM的java struts2框架web應用程序。我們使用mysql作爲我們的數據庫。

我們在日誌中發現了一些DB相關的異常。在配置的時間之前超時連接到數據庫。這裏是我們發現的共同特例。

104343235 [pool-6-thread-19] ERROR org.hibernate.util.JDBCExceptionReporter - The last packet successfully received from the server was 100,838,460 milliseconds ago. The last packet sent successfully to the server was 100,838,461 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 client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. 

org.hibernate.exception.JDBCConnectionException: could not execute query 
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:99) 
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) 
    at org.hibernate.loader.Loader.doList(Loader.java:2536) 
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2276) 
    at org.hibernate.loader.Loader.list(Loader.java:2271) 
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:452) 
    at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) 
    at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) 
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1268) 
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) 
    at com.myproject.model.dao.entities.EntitiesDAO.getByIds(EntitiesDAO.java:148) 

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 100,838,460 milliseconds ago. The last packet sent successfully to the server was 100,838,461 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 client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. 
    at sun.reflect.GeneratedConstructorAccessor345.newInstance(Unknown Source)104343242 [pool-6-thread-16] ERROR org.hibernate.util.JDBCExceptionReporter - The last packet successfully received from the server was 100,838,544 milliseconds ago. The last packet sent successfully to the server was 100,838,544 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 client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. 
104343242 [pool-6-thread-16] ERROR org.hibernate.util.JDBCExceptionReporter - The last packet successfully received from the server was 100,838,544 milliseconds ago. The last packet sent successfully to the server was 100,838,544 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 client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. 

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) 
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525) 
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) 
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1117) 
    at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3829) 
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2449) 
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629) 
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2719) 
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155) 
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2318) 
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76) 
    at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208) 
    at org.hibernate.loader.Loader.getResultSet(Loader.java:1953) 
    at org.hibernate.loader.Loader.doQuery(Loader.java:802) 
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274) 
    at org.hibernate.loader.Loader.doList(Loader.java:2533) 
    ... 21 more 

我們每天都重新啓動我們的應用服務器，作爲該問題的臨時解決方案。

任何幫助將不勝感激。

Answer 1

發生這種情況是因爲MySQL服務器在超時後終止沒有活動的連接。 你需要幾行添加到DBCP配置 嘗試添加下列參數：

validationQuery="SELECT 1" 
testOnBorrow="true 

工作原理：連接池試圖返回連接之前運行validationQuery。如果validationQuesry失敗，dbcp將放棄連接，創建一個新連接並將其返回。

下面是一個例子：

<Resource name="jdbc/cooldatabase" 
      description="Strandls.com license database" 
      auth="Container" 
      type="javax.sql.DataSource" 
      factory="org.apache.tomcat.dbcp.dbcp.BasicDataSourceFactory" 
      driverClassName="com.mysql.jdbc.Driver" 
      url="jdbc:mysql://localhost:3306/cooldatabase?autoReconnect=true" 
      username="cooluser" 
      password="coolpassword" 
      initialSize="0" 
      maxActive="20" 
      maxIdle="10" 
      minIdle="0" 
      maxWait="-1" 
      validationQuery="SELECT 1" 
      testOnBorrow="true" 
      poolPreparedStatements="true" 
      removeAbandoned="true" 
      removeAbandonedTimeout="60" 
      logAbandoned="true"/> 

您可以在這裏找到完整的詳細信息：http://amitcodes.wordpress.com/2008/07/26/16/

Answer 2

使用與Hibernate連接池。例如c3p0https://community.jboss.org/wiki/HowToConfigureTheC3P0ConnectionPool。