Programatically Querying Values from Garbage Collector Manager MBean
Querying attribute values from some MBean are very easy such as : Available
Object mbeanObjectName =new ObjectName("java.lang:type=OperatingSystem");
Object attribute = _mbsc.getAttribute(mbeanObjectName,"AvailableProcessors");
My question is... Is there an easy way to query values such as
LastGcInfo injava.lang:type=GarbageCollector,name=MarkSweepCompact
Inside this attribute, the value formemoryUsageAfterGcis a type of Map (TablularData). The tablular data contains a key and value pair. I am afterPerm Gen. The value is a CompositeData type.
After drilling all the way in, I arive at the value I am after "used".
Is there an easy way to query this value directly? Maybe through getAttribute?
Or, is the only way to write a lot of code and iterating through the maps and composite data?
[973 byte] By [
Shawn@@a] at [2007-11-26 22:36:21]
# 1
Hi,
Use ManagementFactory.newPlatformMXBeanProxy as I have described here:
"How To Retrieve Remote JVM Monitoring And Management Information"
http://blogs.sun.com/jmxetc/entry/how_to_retrieve_remote_jvm
best regards,
-- daniel
JMX, SNMP, Java, etc...
http://blogs.sun.com/jmxetc
# 2
By far the easiest way of dealing with MXBeans programmatically is through MXBean proxies. You can do this:
import com.sun.management.GarbageCollectorMXBean;
import com.sun.management.GcInfo;
...other imports from java.*...
GarbageCollectorMXBean gcm =
ManagementFactory.newPlatformMXBeanProxy(
_mbsc, "java.lang:type=GarbageCollector,name=MarkSweepCompact",
GarbageCollectorMXBean.class);
GcInfo gci = gcm.getLastGcInfo();
Map<String, MemoryUsage> map = gci.getMemoryUsageAfterGc();
MemoryUsage mu = map.get("PS Perm Gen");
long used = mu.getUsed();
It's still a fair amount of code, but you don't need to iterate over anything or look at CompositeData ever.
The com.sun.management interfaces used here are documented at http://java.sun.com/javase/6/docs/jre/api/management/extension/overview-summary.html
Regards,
蒩monn McManus -- JMX Spec Lead -- http://weblogs.java.net/blog/emcmanus
# 3
Thanks for the replies. Duke stars to each of you.
I ended up going a more generic route using JXPath http://jakarta.apache.org/commons/jxpath/ and writing custom DynamicPropertyHandlers for compositedata and tabulardata.
Now I can collect just about any value using three parameters such as
"java.lang:type=GarbageCollector,name=PS MarkSweep", "LastGcInfo", "memoryUsageAfterGc[@name='PS Old Gen']/used"
