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https://issues.apache.org/jira/browse/VELOCITY-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17725811#comment-17725811
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Marinó A. Jónsson commented on VELOCITY-965:
--------------------------------------------
* There is no need to share the Statement for fetching the timestamp as it just
returns a value and not a Reader - so this particular error is easily fixed
(the readLastModified method isn't even synchronized).
* However, according to the stackoverflow discussion it seems that if the same
Statement is executed twice the second query will close the previous ResultSet
- so this implementation is not thread-safe even though the getResourceReader
method is synchronized ... if two templates are being fetched at the same time
the second query could easily close the first ResultSet for the first query
before the Reader has finished reading.
> Velocity 1.7 vs velocity 2.3: Getting thread synchronization issue
> ------------------------------------------------------------------
>
> Key: VELOCITY-965
> URL: https://issues.apache.org/jira/browse/VELOCITY-965
> Project: Velocity
> Issue Type: Bug
> Components: Engine
> Affects Versions: 2.3
> Reporter: Amrit
> Priority: Major
>
> Recently we migrated from Velocity 1.7 to Velocity 2.3. We see the below
> error intermittently which is a possible thread synchronization issue with
> Velocity Engine. The resultset is getting closed while another thread is
> making use of it.
> {noformat}
> 2023-04-15 10:36:33.472 ERROR [org.apache.velocity.loader.ds]
> {344} - DataSourceResourceLoader: database problem while getting timestamp of
> 'xyz_abc':
> java.sql.SQLException: Closed Resultset: next
> at
> oracle.jdbc.driver.InsensitiveScrollableResultSet.ensureOpen(InsensitiveScrollableResultSet.java:109)
> ~[ojdbc8.jar:12.2.0.1.0]
> at
> oracle.jdbc.driver.InsensitiveScrollableResultSet.next(InsensitiveScrollableResultSet.java:398)
> ~[ojdbc8.jar:12.2.0.1.0]
> at
> weblogic.jdbc.wrapper.ResultSet_oracle_jdbc_driver_ForwardOnlyResultSet.next(Unknown
> Source) ~[CodeGenerator.class:12.2.1.3]
> at
> org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader.readLastModified(DataSourceResourceLoader.java:326)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.runtime.resource.loader.DataSourceResourceLoader.getLastModified(DataSourceResourceLoader.java:240)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:446)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:346)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1677)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1656)
> ~[velocity-engine-core-2.3.jar:2.3]
> at
> org.apache.velocity.app.VelocityEngine.getTemplate(VelocityEngine.java:314)
> ~[velocity-engine-core-2.3.jar:2.3]
> {noformat}
> Reference:
> https://stackoverflow.com/questions/2794167/is-resultset-thread-safe
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