Re: JNDI, DataSource, and ClassCastException

Jon Wingfield Thu, 11 Dec 2003 04:58:48 -0800

It looks like a ClassLoader issue. Casting the same class loaded by two different CLs causes a ClassCastException. Have you got the jar containing org.enhydra.jdbc.pool.StandardXAPoolDataSource in more than one place?

http://jakarta.apache.org/tomcat/tomcat-4.1-doc/class-loader-howto.html

HTH,

Jon

Marc Dugger wrote:

I have a situation where I am attempting to downcast a DataSource resource
into the exact class that getClass().getName() reports the object is, but
it's causing a ClassCastException.

--> server.xml:

<GlobalNamingResources>
        <Resource name="LoanAuditorDB" auth="Container"
type="org.enhydra.jdbc.pool.StandardXAPoolDataSource"/>
        <ResourceParams name="LoanAuditorDB">
...more
        </ResourceParams>
</GlobalNamingResources>
...more
<Context path="/workbench"
docBase="C:\Code\loanauditor\src\webapp\workbench"

workDir="C:\Code\loanauditor\src\webapp\workbench\WEB-INF\work"
reloadable="true" debug="0">
            <ResourceLink name="jdbc/loanauditor"
                          global="LoanAuditorDB"

type="org.enhydra.jdbc.pool.StandardXAPoolDataSource"/>
            <ResourceLink name="jta/loanauditor"
                          global="UserTransaction"
                          type="javax.transaction.UserTransaction"/>
        </Context>

--> web.xml

<resource-ref>
        <description>DB Connection</description>
        <res-ref-name>jdbc/loanauditor</res-ref-name>
        <res-type>org.enhydra.jdbc.pool.StandardXAPoolDataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

--> constructor from abstract class, AbstractDAO.java:

protected AbstractDAO() {
        try {
            Context ctx = new InitialContext();
            Object o = ctx.lookup("java:comp/env/jdbc/loanauditor");
            log.debug("loanauditor from JNDI: " + o.getClass().getName());
            ds = (org.enhydra.jdbc.pool.StandardXAPoolDataSource) o;
            ds.setJdbcTestStmt("SELECT 1");
        } catch (NamingException ne) {
            log.fatal(ne.getMessage(), ne);
            throw new RuntimeException(ne);
        }
    }

--> logging:

2003-12-04 05:25:39,157 [main] DEBUG
com.socotech.loanauditor.dao.AbstractDAO - loanauditor from JNDI:
org.enhydra.jdbc.pool.StandardXAPoolDataSource

--> stacktrace:

java.lang.ClassCastException
        at com.socotech.loanauditor.dao.AbstractDAO.<init>(AbstractDAO.java:31)
        at
com.socotech.loanauditor.dao.TorqueDomainTypeDAO.<init>(TorqueDomainTypeDAO.
java:34)
        at
com.socotech.loanauditor.dao.TorqueDomainTypeDAO.getInstance(TorqueDomainTyp
eDAO.java:29)
        at
com.socotech.loanauditor.dao.DAOFactory.getDomainTypeDAO(DAOFactory.java:79)
        at
com.socotech.loanauditor.web.listener.DomainTypeLoader.contextInitialized(Do
mainTypeLoader.java:32)
        at
org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:
3271)
        at
org.apache.catalina.core.StandardContext.start(StandardContext.java:3613)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1188)
        at org.apache.catalina.core.StandardHost.start(StandardHost.java:754)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1188)
        at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:363)
        at org.apache.catalina.core.StandardService.start(StandardService.java:497)
        at org.apache.catalina.core.StandardServer.start(StandardServer.java:2190)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:512)
        at org.apache.catalina.startup.Catalina.execute(Catalina.java:400)
        at org.apache.catalina.startup.Catalina.process(Catalina.java:180)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39
)
        at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl
.java:25)
        at java.lang.reflect.Method.invoke(Method.java:324)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:203)

Thanks in advance for any insight.

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Re: JNDI, DataSource, and ClassCastException

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