Interface DiagnosticCommandMBean

All Superinterfaces:

public interface DiagnosticCommandMBean extends DynamicMBean
Management interface for the diagnostic commands for the HotSpot Virtual Machine.

The DiagnosticCommandMBean is registered to the platform MBeanServer as are other platform MBeans.

The ObjectName for uniquely identifying the diagnostic MBean within an MBeanServer is:

This MBean is a DynamicMBean and also a NotificationEmitter. The DiagnosticCommandMBean is generated at runtime and is subject to modifications during the lifetime of the Java virtual machine. A diagnostic command is represented as an operation of the DiagnosticCommandMBean interface. Each diagnostic command has:

  • the diagnostic command name which is the name being referenced in the HotSpot Virtual Machine
  • the MBean operation name which is the name generated for the diagnostic command operation invocation. The MBean operation name is implementation dependent
The recommended way to transform a diagnostic command name into a MBean operation name is as follows:
  • All characters from the first one to the first dot are set to be lower-case characters
  • Every dot or underline character is removed and the following character is set to be an upper-case character
  • All other characters are copied without modification

The diagnostic command name is always provided with the meta-data on the operation in a field named (see below).

A diagnostic command may or may not support options or arguments. All the operations return String and either take no parameter for operations that do not support any option or argument, or take a String[] parameter for operations that support at least one option or argument. Each option or argument must be stored in a single String. Options or arguments split across several String instances are not supported.

The distinction between options and arguments: options are identified by the option name while arguments are identified by their position in the command line. Options and arguments are processed in the order of the array passed to the invocation method.

Like any operation of a dynamic MBean, each of these operations is described by MBeanOperationInfo instance. Here's the values returned by this object:

The Descriptor is a collection of fields containing additional meta-data for a JMX element. A field is a name and an associated value. The additional meta-data provided for an operation associated with a diagnostic command are described in the table below:

dcmd.nameString The original diagnostic command name (not the operation name)
dcmd.descriptionString The diagnostic command description
dcmd.helpString The full help message for this diagnostic command (same output as the one produced by the 'help' command)
dcmd.vmImpactString The impact of the diagnostic command, this value is the same as the one printed in the 'impact' section of the help message of the diagnostic command, and it is different from the getImpact() of the MBeanOperationInfo
dcmd.enabledboolean True if the diagnostic command is enabled, false otherwise
dcmd.permissionClassString Some diagnostic command might require a specific permission to be executed, in addition to the MBeanPermission to invoke their associated MBean operation. This field returns the fully qualified name of the permission class or null if no permission is required
dcmd.permissionNameString The fist argument of the permission required to execute this diagnostic command or null if no permission is required
dcmd.permissionActionString The second argument of the permission required to execute this diagnostic command or null if the permission constructor has only one argument (like the ManagementPermission) or if no permission is required
dcmd.argumentsDescriptor A Descriptor instance containing the descriptions of options and arguments supported by the diagnostic command (see below)

The description of parameters (options or arguments) of a diagnostic command is provided within a Descriptor instance. In this Descriptor, each field name is a parameter name, and each field value is itself a Descriptor instance. The fields provided in this second Descriptor instance are described in the table below:

dcmd.arg.nameString The name of the parameter
dcmd.arg.typeString The type of the parameter. The returned String is the name of a type recognized by the diagnostic command parser. These types are not Java types and are implementation dependent.
dcmd.arg.descriptionString The parameter description
dcmd.arg.isMandatoryboolean True if the parameter is mandatory, false otherwise
dcmd.arg.isOptionboolean True if the parameter is an option, false if it is an argument
dcmd.arg.isMultipleboolean True if the parameter can be specified several times, false otherwise

When the set of diagnostic commands currently supported by the Java Virtual Machine is modified, the DiagnosticCommandMBean emits a Notification with a type of "" and a userData that is the new MBeanInfo.