Re: AbstractJdbc2ResultSet.FAST_NUMBER_FAILED brings class loader leak

Hello, I'm working on fixing the issue "java.lang.OutOfMemoryError:
Metaspace" in the time of redeploy where running an web application on
Tomcat.

I have acquired a heap dump and found a weird Root GC reference which is
connected to org.postgresql.jdbc2.AbstractJdbc2ResultSet. The heap dump
shows that it saves a (intentionally constructed) NumberFormatException
in a private static final field FAST_NUMBER_FAILED and that field has
backtrace field which references a Servlet class that loaded by
WebappClassLoader.

Here's a screenshot of Eclipse Memory Analyzer:
http://www.nailedtothex.org/roller/kyle/mediaresource/2fabd2a0-10a3-4d45-b8c8-589763d15824

I think AbstractJdbc2ResultSet should stop saving a intentionally
constructed Exception in a static field because it creates a strong
reference to a class which invoked the database operation at the first
time regardless if it's loaded by WebappClassLoader. It will be a cause
of class loader leak.

[Steps to reproduce]

1. Put postgresql-9.3-1100.jdbc41.jar to $TOMCAT_HOME/lib
2. Put following element to $TOMCAT_HOME/conf/context.xml

    <Resource name="jdbc/PostgreSQLDS"
              url="jdbc:postgresql://localhost:5432/somedb"
              driverClassName="org.postgresql.Driver"
              username="postgres"
              password="***"
              auth="Container"
              type="javax.sql.DataSource"
              maxActive="20"
              maxIdle="5"
              maxWait="10000"/>

3. git clone https://github.com/lbtc-xxx/jdbc-servlet
4. cd jdbc-servlet; mvn clean package
5. deploy the WAR
6. visit http://localhost:8080/jdbc-servlet-1.0-SNAPSHOT
7. undeploy and deploy the WAR several times (keep your JVM running)
8. acquire heap dump and load it with Eclipse Memory Analyzer

[My environment]

* postgresql-9.3-1100.jdbc41.jar
* Tomcat 8.0.18
* Oracle JDK 8u60
* PostgreSQL 9.3.4

Thanks.


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