Known Limitations

The following restrictions apply to Java Dynamic Management Kit 4.0, they can explain inconsistent behavior and suggest a workaround:

Specification Version String

The MBean server delegate object exposes the read-only SpecificationVersion attribute of type String. This attribute currently returns "2.0 Second Public Release" when it should return the full version number of the JMX specification which is currently "1.0 Public Release 2".

SNMPv2 Protocol

InformRequest and Report PDUs are not supported.

The mibgen Tool

The mibgen tool cannot handle the following constructs:

• Nested groups - reports an error and fails to compile the MIB

• Row status - doesn't cause an error or interrupt compilation, but no special support is provided for the semantics of RowStatus variables (as defined in RFC 1903).

The HTML Adaptor

Due to the limitations of the HTML protocol, the HTML adaptor does not provide the same management view as a connector. For example, you cannot set attributes individually in the MBean view--all setters are called every time the "Apply" button is selected, even if the content hasn't changed.

Also, the HTML adaptor can only represent a limited set of types through an HTML interface. Any attribute or operation which relies on an unsupported type does not appear. This means that some component functionality is inaccessible through the HTML adaptor.

Tutorial

The tutorial doesn't cover all of the sample applications found in the examples directory. All of the examples include detailed README files and well-commented code. In addition, certain topics can be found elsewhere:

• Notifications are well covered in the JMX instrumentation specification

• The MBean registration process is covered in the JMX agent specification

• Proxy MBeans are introduced in Getting Started with the Java Dynamic Management Kit 4.0

• The monitoring and timer services are covered in the JMX agent specification

JDK 1.1.8 and Native Threads

When running the JDK 1.1.8 virtual machine with native threads and using an HTTP connector client, an unexpected java.lang.ClassCastException is sometimes thrown. The workaround to this problem is to deactivate the keep-alive feature of the java.net.HttpURLConnection class. You can do this by running your application with the following property definition on the command line:

$ java -Dhttp.keepAlive=false yourApplication

Windows NT and the JIT Compiler

The JIT (just in time) compiler of the Java virtual machine on the Windows NT platform can cause Java Dynamic Management application to fail. It is recommended to disable the JIT compiler on the Windows NT platform.

Green Threads

Using green threads when running with a Java virtual machine other than a production release is also a known source of errors. Avoid using this combination to minimize the risk of unexplained failures. Please refer to the JDK documentation for more information about native and green threads.