java.lang.management

Platform MXBeans

Management Interface	Description
{@link java.lang.management.ClassLoadingMXBean}	Class loading system of the Java virtual machine.
{@link java.lang.management.CompilationMXBean}	Compilation system of the Java virtual machine.
{@link java.lang.management.MemoryMXBean}	Memory system of the Java virtual machine.
{@link java.lang.management.ThreadMXBean}	Threads system of the Java virtual machine.
{@link java.lang.management.RuntimeMXBean}	Runtime system of the Java virtual machine.
{@link java.lang.management.OperatingSystemMXBean}	Operating system on which the Java virtual machine is running.
{@link java.lang.management.GarbageCollectorMXBean}	Garbage collector in the Java virtual machine.
{@link java.lang.management.MemoryManagerMXBean}	Memory manager in the Java virtual machine.
{@link java.lang.management.MemoryPoolMXBean}	Memory pool in the Java virtual machine.

A platform MXBean is a managed bean that defines the management interface for one component for the platform and is specified in the ManagementFactory class.

An application can monitor the instrumentation of the Java virtual machine and manage certain characteristics in the following ways:

• Direct access to an MXBean interface
  1. Get the MXBean instance through the static factory method and access the MXBean interface locally of the running virtual machine.
  2. Construct an MXBean proxy instance that forwards the method calls to a given {@link javax.management.MBeanServer MBeanServer} by calling {@link java.lang.management.ManagementFactory#newPlatformMXBeanProxy ManagementFactory.newPlatformMXBeanProxy}. A proxy is typically constructed to remotely access an MXBean of another running virtual machine.
• Indirect access via {@link javax.management.MBeanServer MBeanServer} interface
  1. Go through the {@link java.lang.management.ManagementFactory#getPlatformMBeanServer platform MBeanServer} to access MXBeans locally or a specific MBeanServerConnection to access MXBeans remotely. The attributes and operations of an MXBean use only JMX open types which include basic data types, {@link javax.management.openmbean.CompositeData CompositeData}, and {@link javax.management.openmbean.TabularData TabularData} defined in {@link javax.management.openmbean.OpenType OpenType}.

ManagementFactory

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 platform MXBeans defined in other packages such as {@link java.util.logging.LoggingMXBean}. Each platform MXBean is registered with a unique name defined in the {@link java.lang.management.ManagementFactory ManagementFactory} class for constructing {@link javax.management.ObjectName ObjectName}. This is a single MBeanServer that can be shared by different managed components running within the same Java virtual machine.

Interoperability

A data type used by the MXBean interfaces are mapped to an open type when being accessed via MBeanServer interface. The data type mapping is specified in the {@link java.lang.management.ManagementFactory ManagementFactory} class.

Ways to Access MXBeans

1. Call the methods in the MXBean directly within the same Java virtual machine.

      RuntimeMXBean mxbean = ManagementFactory.getRuntimeMXBean();
   
      // Get the standard attribute "VmVendor"
      String vendor = mxbean.getVmVendor();
   
   

2. Go through a MBeanServerConnection connecting to the platform MBeanServer of a running virtual machine.

   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
       ...
   }

3. Use MXBean proxy.

   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 = 
       ManagementFactory.newPlatformMXBeanProxy(mbs,
                                                ManagementFactory.RUNTIME_MXBEAN_NAME,
                                                RuntimeMXBean.class);
   // Get standard attribute "VmVendor" 
   String vendor = proxy.getVmVendor();

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 a platform-specific attribute from Sun's implementation of the RuntimeMXBean.

1) Direct access to the Sun-specific MXBean interface

   com.sun.management.RuntimeMXBean mxbean = 
       (com.sun.management.RuntimeMXBean) ManagementFactory.getRuntimeMXBean();

   // Get the standard attribute "VmVendor"
   String vendor = mxbean.getVmVendor();

   // Get the platform-specific attribute "Bar"
   BarType bar = mxbean.getBar();

2) Access the Sun-specific 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");

       // Check if this MXBean contains Sun's extension
       if (mbs.isInstanceOf(oname, "com.sun.management.RuntimeMXBean")) {
           // Get platform-specific attribute "Bar"
           BarType bar = (String) mbs.getAttribute(oname, "Bar");
       }
   } catch (....) {
       // Catch the exceptions thrown by ObjectName constructor
       // and MBeanServer methods
       ...
   }

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 @version 1.17, 05/05/07 @since 1.5

A Java virtual machine has a single instance of the implementation class of this interface.

The following table provides a summary description of what the permission allows, and discusses the risks of granting code the permission.

Permission Target Name	What the Permission Allows	Risks of Allowing this Permission
control	Ability to control the runtime characteristics of the Java virtual machine, for example, setting the -verbose:gc and -verbose:class flag, setting the threshold of a memory pool, and enabling and disabling the thread contention monitoring support.
MemoryManagerMXBean.java	Interface	The management interface for a memory manager.
MemoryMXBean.java	Interface	The management interface for the memory system of the Java virtual machine. A Java virtual machine has a single instance of the implementation class of this interface.
MemoryNotificationInfo.java	Class	The information about a memory notification. A memory notification is emitted by MemoryMXBean when the Java virtual machine detects that the memory usage of a memory pool is exceeding a threshold value.
MemoryPoolMXBean.java	Interface	The management interface for a memory pool.
MemoryType.java	enum	Types of MemoryPoolMXBean memory pools .
MemoryUsage.java	Class	A MemoryUsage object represents a snapshot of memory usage. Instances of the MemoryUsage class are usually constructed by methods that are used to obtain memory usage information about individual memory pool of the Java virtual machine or the heap or non-heap memory of the Java virtual machine as a whole. A MemoryUsage object contains four values: init represents the initial amount of memory (in bytes) that the Java virtual machine requests from the operating system for memory management during startup. MonitorInfo.java Class Information about an object monitor lock. OperatingSystemMXBean.java Interface The management interface for the operating system on which the Java virtual machine is running. A Java virtual machine has a single instance of the implementation class of this interface. RuntimeMXBean.java Interface The management interface for the runtime system of the Java virtual machine. A Java virtual machine has a single instance of the implementation class of this interface. ThreadInfo.java Class Thread information. ThreadMXBean.java Interface The management interface for the thread system of the Java virtual machine. A Java virtual machine has a single instance of the implementation class of this interface.