Java Database Connectivity (JDBC)

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JDBC, MySQL, Communications link failure

843859Feb 23 2007 — edited Mar 1 2007

hello

i have a client that connects to remote MySQL database, using Hibernate as persistence layer, and c3p0 as connection pool. Database is really ancient MySQL 3.23.58, but i can't do anything about that.

I need to have one session open for the whole time the client is running.
But, when a client is inactive for a few minutes, and then needs to get data from the database, i get following exception...

org.hibernate.exception.JDBCConnectionException: could not initialize a collection: [imarine2.Category.stuff#547]
        at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
        at org.hibernate.loader.Loader.loadCollection(Loader.java:1992)
        at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
        at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565)
        at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
        at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716)
        at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:454)
        at org.hibernate.Hibernate.initialize(Hibernate.java:309)
        at imarine2.StuffLoader.run(StuffLoader.java:61)
        at java.lang.Thread.run(Thread.java:595)
Caused by: com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.io.EOFException

STACKTRACE:

java.io.EOFException
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1913)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2304)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
        at com.mysql.jdbc.Connection.execSQL(Connection.java:3176)
        at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1153)
        at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1266)
        at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76)
        at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:186)
        at org.hibernate.loader.Loader.getResultSet(Loader.java:1778)
        at org.hibernate.loader.Loader.doQuery(Loader.java:662)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
        at org.hibernate.loader.Loader.loadCollection(Loader.java:1985)
        at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
        at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565)
        at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
        at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716)
        at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:454)
        at org.hibernate.Hibernate.initialize(Hibernate.java:309)
        at imarine2.StuffLoader.run(StuffLoader.java:61)
        at java.lang.Thread.run(Thread.java:595)


** END NESTED EXCEPTION **



Last packet sent to the server was 1 ms ago.
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2515)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
        at com.mysql.jdbc.Connection.execSQL(Connection.java:3176)
        at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1153)
        at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1266)
        at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76)
        at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:186)
        at org.hibernate.loader.Loader.getResultSet(Loader.java:1778)
        at org.hibernate.loader.Loader.doQuery(Loader.java:662)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
        at org.hibernate.loader.Loader.loadCollection(Loader.java:1985)
        ... 8 more

here are excerpts from hibernate.config:

hibernate.connection.driver_class=com.mysql.jdbc.Driver
hibernate.connection.url=jdbc\:mysql\://XX.XX.XX.XX/XXXX
hibernate.dialect=org.hibernate.dialect.MySQLDialect
hibernate.connection.useUnicode=true
hibernate.connection.characterEncoding=Cp1250
hibernate.jdbc.batch_size=50
hibernate.c3p0.acquire_increment=3
hibernate.c3p0.idle_test_period=600
hibernate.c3p0.timeout=600
hibernate.c3p0.min_size=1
hibernate.c3p0.max_size=100
hibernate.c3p0.max_statements=100

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Locked on Mar 29 2007

Added on Feb 23 2007

#java-database-connectivity-jdbc

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