Limitations#

Classes that exist only in the application#

ajmx cannot deserialize values and exceptions of classes that exist only in the target application, and cannot send values that are not serializable. Both fail with UNSUPPORTED_TYPE, as do JDK classes the native binary leaves out, such as those of java.desktop.

MXBeans and most JDK MBeans use only open types, such as CompositeData, so ajmx reads them. For an MBean that returns its own classes, read a related attribute or operation that returns open types instead.

Enums of Standard MBeans#

An attribute of a Standard MBean whose type is an application-defined enum can be neither read nor written. MXBean enums work, as strings.

Types that write and invoke accept#

write and invoke accept:

  • primitives and their wrappers
  • String, ObjectName, BigInteger and BigDecimal
  • one-dimensional arrays of these

A byte[] is given as an array of numbers from -128 to 127, not as {"$base64": ...}.

JVMs that --pid can attach to#

  • --pid supports HotSpot JVMs of the same user, or of any user for root on Linux. JDK 8 to 25 are tested.
  • It refuses a process that does not look like a HotSpot JVM with ATTACH_NOT_SUPPORTED, because attaching sends SIGQUIT, which kills many processes that are not JVMs.
  • --pid starts the local JMX agent in the target JVM. It stays until the JVM restarts.

See Local JVMs.

No TLS settings for --url#

ajmx has no TLS settings, such as a trust store or a client certificate. It is tested against JVMs started with com.sun.management.jmxremote.ssl=false. See Remote JVMs.

JVMs that ps does not list#

ps does not list JVMs started with -XX:-UsePerfData or -XX:+PerfDisableSharedMem. --pid still connects to them if they run the java launcher.

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