Java configuration (optional)

Transport and codec plug-ins written in Java are executed by the IAF inside an embedded Java Virtual Machine (JVM). The optional <java> element allows the environment of this JVM to be configured.

The <java> element may contain zero or more of the following nested elements:

<classpath> – This element adds a single entry onto the JVM classpath, which is the list of paths used by Java to locate classes. Each <classpath> element has a single path attribute that specifies a directory or Java Archive file (.jar) to add to the classpath.

The full classpath used by the IAF's JVM is made up by concatenating (in order):

1. the contents of the APAMA_IAF_CLASSPATH environment variable if one is defined,

2. each of the path entries specified by <classpath> elements, in the order they appear in the configuration file, OR if there are none, the contents of the CLASSPATH environment variable,

3. the path of the lib/JPlugin_internal.jar file used internally by the IAF.

Additionally, if a jarName attribute is used in the <codec> or <transport> element that defines a plug-in (as in Transport and codec plug-in configuration), the plug-in will be loaded using a new classloader with access to the specified Java Archive in addition to the JVM classpath.

You should make sure that all shared classes are in a separate jar that is specified by a <classpath> element. The shared classes are then loaded by the parent classloader. This ensures that when a codec or transport references a shared class, they both agree it is the same class.

<jvm-option> – This element allows arbitrary JVM command-line options to be specified. The JVM option should be placed between the start and end jvm-option tags. For example:

<jvm-option>-Xmx256m</jvm-option>

See the usage screen of the JVM's Java executable for a full list of supported options.

<property> – This element specifies a Java system property that should be passed to the JVM. It has name and value attributes, such that using:

is a shorthand equivalent to:

<jvm-option>-DpropName=propValue</jvm-option>

See The IAF runtime for a description of how the IAF selects the JVM library to use.

The properties specified in the <java> element cannot be changed once the JVM has been loaded by the IAF. This will occur when the IAF reads a configuration file that specifies a Java transport or codec plug-in. If the same IAF process is later reconfigured to use only C/C++ transports, the JVM will not be unloaded. The IAF will log a warning message if a reconfiguration of the IAF process attempts to change the previously configured JVM properties.