+A platform MXBean is a managed bean that +conforms to the JMX +Instrumentation Specification and only uses a set of basic data types. +Each platform MXBean is a {@link java.lang.management.PlatformManagedObject} +with a unique +{@linkplain java.lang.management.PlatformManagedObject#getObjectName name}. +
The {@link java.lang.management.ManagementFactory} class is the management +factory class for the Java platform. This class provides a set of +static factory methods to obtain the MXBeans for the Java platform +to allow an application to access the MXBeans directly. + +
A platform MBeanServer can be accessed with the +{@link java.lang.management.ManagementFactory#getPlatformMBeanServer + getPlatformMBeanServer} method. On the first call to this method, +it creates the platform MBeanServer and registers all platform MXBeans +including {@linkplain java.lang.management.PlatformManagedObject +platform MXBeans}. +Each platform MXBean is registered with a unique name defined in +the specification of the management interface. +This is a single MBeanServer that can be shared by different managed +components running within the same Java virtual machine. + +
A management application and a platform MBeanServer of a running +virtual machine can interoperate +without requiring classes used by the platform MXBean interfaces. +The data types being transmitted between the JMX connector +server and the connector client are JMX +{@linkplain javax.management.openmbean.OpenType open types} and +this allows interoperation across versions. +A data type used by the MXBean interfaces are mapped to an +open type when being accessed via MBeanServer interface. +See the +MXBean specification for details. + +
An application can monitor the instrumentation of the +Java virtual machine and the runtime in the following ways: +
+1. Direct access to an MXBean interface +
+ RuntimeMXBean mxbean = ManagementFactory.getRuntimeMXBean(); + + // Get the standard attribute "VmVendor" + String vendor = mxbean.getVmVendor(); ++
Or by calling the + {@link java.lang.management.ManagementFactory#getPlatformMXBean(Class) + getPlatformMXBean} or + {@link java.lang.management.ManagementFactory#getPlatformMXBeans(Class) + getPlatformMXBeans} method: +
+ RuntimeMXBean mxbean = ManagementFactory.getPlatformMXBean(RuntimeMXBean.class); + + // Get the standard attribute "VmVendor" + String vendor = mxbean.getVmVendor(); ++
+ MBeanServerConnection mbs;
+
+ // Connect to a running JVM (or itself) and get MBeanServerConnection
+ // that has the JVM MBeans registered in it
+ ...
+
+ // Get a MBean proxy for RuntimeMXBean interface
+ RuntimeMXBean proxy =
+ {@link java.lang.management.ManagementFactory#getPlatformMXBean(MBeanServerConnection, Class)
+ ManagementFactory.getPlatformMXBean}(mbs,
+ RuntimeMXBean.class);
+ // Get standard attribute "VmVendor"
+ String vendor = proxy.getVmVendor();
+
+A proxy is typically used to access an MXBean + in a remote Java virtual machine. + An alternative way to create an MXBean proxy is: +
+ RuntimeMXBean proxy =
+ {@link java.lang.management.ManagementFactory#newPlatformMXBeanProxy
+ ManagementFactory.newPlatformMXBeanProxy}(mbs,
+ ManagementFactory.RUNTIME_MXBEAN_NAME,
+ RuntimeMXBean.class);
+
++2. Indirect access to an MXBean interface via MBeanServer +
+ MBeanServerConnection mbs;
+
+ // Connect to a running JVM (or itself) and get MBeanServerConnection
+ // that has the JVM MXBeans registered in it
+ ...
+
+ try {
+ // Assuming the RuntimeMXBean has been registered in mbs
+ ObjectName oname = new ObjectName(ManagementFactory.RUNTIME_MXBEAN_NAME);
+
+ // Get standard attribute "VmVendor"
+ String vendor = (String) mbs.getAttribute(oname, "VmVendor");
+ } catch (....) {
+ // Catch the exceptions thrown by ObjectName constructor
+ // and MBeanServer.getAttribute method
+ ...
+ }
+
+A Java virtual machine implementation may add its platform extension to +the management interface by defining platform-dependent +interfaces that extend the standard management interfaces to include +platform-specific metrics and management operations. +The static factory methods in the ManagementFactory class will +return the MXBeans with the platform extension. + +
+It is recommended to name the platform-specific attributes with +a vendor-specific prefix such as the vendor's name to +avoid collisions of the attribute name between the future extension +to the standard management interface and the platform extension. +If the future extension to the standard management interface defines +a new attribute for a management interface and the attribute name +is happened to be same as some vendor-specific attribute's name, +the applications accessing that vendor-specific attribute would have +to be modified to cope with versioning and compatibility issues. + +
Below is an example showing how to access an attribute +from the platform extension: + +
+1) Direct access to the Oracle-specific MXBean interface +
+
+ List<com.sun.management.GarbageCollectorMXBean> mxbeans =
+ ManagementFactory.getPlatformMXBeans(com.sun.management.GarbageCollectorMXBean.class);
+
+ for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) {
+ // Get the standard attribute "CollectionCount"
+ String count = mxbean.getCollectionCount();
+
+ // Get the platform-specific attribute "LastGcInfo"
+ GcInfo gcinfo = gc.getLastGcInfo();
+ ...
+ }
+
+
+
++2) Access the Oracle-specific MXBean interface via MBeanServer + through proxy + +
+ MBeanServerConnection mbs;
+
+ // Connect to a running JVM (or itself) and get MBeanServerConnection
+ // that has the JVM MXBeans registered in it
+ ...
+
+ List<com.sun.management.GarbageCollectorMXBean> mxbeans =
+ ManagementFactory.getPlatformMXBeans(mbs, com.sun.management.GarbageCollectorMXBean.class);
+
+ for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) {
+ // Get the standard attribute "CollectionCount"
+ String count = mxbean.getCollectionCount();
+
+ // Get the platform-specific attribute "LastGcInfo"
+ GcInfo gcinfo = gc.getLastGcInfo();
+ ...
+ }
+Unless otherwise noted, passing a null argument to a constructor +or method in any class or interface in this package will cause a {@link +java.lang.NullPointerException NullPointerException} to be thrown. + +
The java.lang.management API is thread-safe. + +@see + JMX Specification. + +@author Mandy Chung +@since 1.5 + + +