[ mx4j-Bugs-1031741 ] Caching Support In Required Model MBean Is Broken

Bugs item #1031741, was opened at 2004-09-21 10:41
Message generated for change (Comment added) made by emcmanus
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=450647&aid=1031741&group_id=47745

Category: JMX implementation
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: Caching Support In Required Model MBean Is Broken

Initial Comment:
The following class is a JUnit test case which
demonstrates that two RequiredModelMBeans which share
the same ModelMBeanInfo class also share the same
attribute cache which leads to incorrect behaviour when
caching is enabled [ attribute values are aliased
between MBean instances ].

Both tests should pass, but only testWithoutCache does.

For more information about this testcase, write to
[email protected].


/*
 * Created on 21/09/2004
 *
 */
package bugs;

import javax.management.Attribute;
import javax.management.AttributeNotFoundException;
import javax.management.Descriptor;
import javax.management.InstanceNotFoundException;
import javax.management.InvalidAttributeValueException;
import javax.management.MBeanException;
import javax.management.ReflectionException;
import javax.management.modelmbean.DescriptorSupport;
import
javax.management.modelmbean.InvalidTargetObjectTypeException;
import javax.management.modelmbean.ModelMBeanAttributeInfo;
import
javax.management.modelmbean.ModelMBeanConstructorInfo;
import javax.management.modelmbean.ModelMBeanInfo;
import javax.management.modelmbean.ModelMBeanInfoSupport;
import
javax.management.modelmbean.ModelMBeanNotificationInfo;
import javax.management.modelmbean.ModelMBeanOperationInfo;
import javax.management.modelmbean.RequiredModelMBean;

import junit.framework.TestCase;

/**
 * @author jseymour
 *
 */
public class CachingBug
	extends TestCase
{
    private String foo;
    public String getFoo()
    {
        return foo;
    }
    public void setFoo(String foo) {
        this.foo = foo;
    }
    
    public void testWithoutCache() throws Exception {    
        theTest(false); 
    }
    
    public void testWithCache() throws Exception {    
        theTest(true); 
    }
    /**
     * @throws MBeanException
     * @throws InstanceNotFoundException
     * @throws InvalidTargetObjectTypeException
     * @throws AttributeNotFoundException
     * @throws InvalidAttributeValueException
     * @throws ReflectionException
     */
    private void theTest(boolean withCache) throws
MBeanException, InstanceNotFoundException,
InvalidTargetObjectTypeException,
AttributeNotFoundException,
InvalidAttributeValueException, ReflectionException {
        Descriptor d = new DescriptorSupport();
        
        if (withCache) {
            d.setField("currencyTimeLimit", "60");
        }
        
        d.setField("name", "foo");
        d.setField("descriptorType", "attribute");
        d.setField("getMethod", "getFoo");
        d.setField("setMethod", "setFoo");
        
        ModelMBeanAttributeInfo fooInfo = new
ModelMBeanAttributeInfo("foo", "java.lang.String", "is
a foo", true, true, false, d);
        ModelMBeanInfoSupport mbi = new
ModelMBeanInfoSupport(CachingBug.class.getName(),
"pojo", new ModelMBeanAttributeInfo[] { fooInfo } , new
ModelMBeanConstructorInfo[] {}, new
ModelMBeanOperationInfo[] {}, new
ModelMBeanNotificationInfo[] {} );
        RequiredModelMBean rmb1 = new
RequiredModelMBean(mbi);
        RequiredModelMBean rmb2 = new
RequiredModelMBean((ModelMBeanInfo)mbi.clone());
        
        CachingBug bar1 = new CachingBug();
        CachingBug bar2 = new CachingBug();
        
        rmb1.setManagedResource(bar1, "ObjectReference");
        rmb2.setManagedResource(bar2, "ObjectReference");
        
        rmb1.setAttribute(new Attribute("foo","bar1"));
        rmb2.setAttribute(new Attribute("foo","bar2"));
        assertEquals("value of rmb1.foo", "bar1",
rmb1.getAttribute("foo")); 
        assertEquals("value of rmb2.foo", "bar2",
rmb2.getAttribute("foo"));
    }
}


----------------------------------------------------------------------

Comment By: Eamonn McManus (emcmanus)
Date: 2004-09-21 10:56

Message:
Logged In: YES 
user_id=770046

For better or worse, RequiredModelMBean is specified to
cache attribute values in the attribute Descriptor. If two
RequiredModelMBeans share the same ModelMBeanInfo, then they
share the same ModelMBeanAttributeInfos and therefore the
same Descriptors for their attributes. As a consequence, if
you enable attribute caching, you cannot share your
MBeanInfo with anyone else.

----------------------------------------------------------------------

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