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https://issues.apache.org/jira/browse/DBCP-533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chengkun Li updated DBCP-533:
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Attachment: (was: 20181221101456927.png)
> tomcat register MBean of BasicDataSource with jmxName , appear
> InstanceAlreadyExistsException
> ---------------------------------------------------------------------------------------------
>
> Key: DBCP-533
> URL: https://issues.apache.org/jira/browse/DBCP-533
> Project: Commons DBCP
> Issue Type: Bug
> Affects Versions: 2.0
> Environment: tomcat 8.5.32
> Reporter: Chengkun Li
> Priority: Major
> Labels: InstanceAlreadyExistsException, jmxName
>
> We use DBCP2 as GlobalNamingResources in tomcat and I need monitoring
> connection of DBCP2 ,but does not find how to use JMX in
> [http://commons.apache.org/proper/commons-dbcp/configuration.html]
> through reading the source code ,i find jmxName properties in
> BasicDataSourceFactory ,when I add the setting like
> jmxName="org.apache.dbcp:DataSource=mydb" in server.xml , there is
> javax.management.InstanceAlreadyExistsException:
> org.apache.dbcp:DataSource=mysqldb when I start up tomcat.
> after I debug the code , i find that DBCP have registered the Mbean in
> BasicDataSource with jmxName (BasicDataSource line 2390).
> {code:java}
> // code placeholder
> private void jmxRegister() {
> // Return immediately if no JMX name has been specified
> final String requestedName = getJmxName();
> if (requestedName == null) {
> return;
> }
> try {
> ObjectNameWrapper.wrap(requestedName).registerMBean(this);
> } catch (final MalformedObjectNameException e) {
> log.warn("The requested JMX name [" + requestedName + "] was not
> valid and will be ignored.");
> }
> }
> {code}
>
> but tomcat will register the Component in the startup lifecycle , tomcat
> will use the BasicDataSource's preRegister method to get the same Mbean name,
> because BasicDataSource implements MBeanRegistration.
> {code:java}
> // code placeholder
> if (("javax.sql.DataSource".equals(ref.getClassName()) ||
> "javax.sql.XADataSource".equals(ref.getClassName())) &&
> resource.getSingleton()) {
> try {
> ObjectName on = createObjectName(resource);
> Object actualResource = envCtx.lookup(resource.getName());
> Registry.getRegistry(null, null).registerComponent(actualResource,
> on, null);
> objectNames.put(resource.getName(), on);
> } catch (Exception e) {
> log.warn(sm.getString("naming.jmxRegistrationFailed", e));
> }
> }
> {code}
> DBCP will register the MBean first ,but when tomcat register it will throw
> the InstanceAlreadyExistsException
> BUT i'm not certain that it's a bug or I use it wrong
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