Embedded JVM configuration

This page describes the configuration items for a C DataSource application’s embedded Java virtual machine (JVM).

For information on configuring the JVM used to run a Java DataSource application, see Configuring a Java DataSource’s JVM.

jvm-global-classpath

jvm-global-classpath specifies the classpath of a C DataSource’s embedded JVM.

You can specify multiple classpaths on the same line, using a space separator, like this:

jvm-global-classpath %r/lib/java/jmx-child-classloader.jar %r/lib/java/common-jmx.jar

You can also specify multiple classpaths, using a separate jvm-global-classpath item for each one; for example:

jvm-global-classpath %r/lib/java/jmx-child-classloader.jar
jvm-global-classpath %r/lib/java/common-jmx.jar

The classpath can contain the %r parameter; at run time, %r is replaced by the root directory (application-root) under which the DataSource application runs, so you can define the classpath location relative to this.

You can also specify a classpath for a specific class, using the classpath option of add-javaclass.

Use in: C

Syntax: jvm-global-classpath <classpath>

Type: array of strings

Default value: %r/lib/java

jvm-location

jvm-location is a C DataSource configuration item that directs the DataSource to run an embedded JVM using a specified JVM library. The embedded JVM is used by the DataSource to host Java modules that extend the DataSource’s functionality (for example, Transformer’s Refiner module).

The JVM location may be specified as an absolute path to a JVM library or a parent directory of a JVM library:

  • Absolute path to a JVM library.

    Example: (RHEL 7) absolute path to an OpenJDK 8 JVM library
    jvm-location /etc/alternatives/java_sdk_1.8.0/jre/lib/amd64/server/libjvm.so

  • Absolute path to a parent directory of a JVM library.

    Requires a C Datasource built with DSDK 7.1.16+ (Liberator 7.1.15+, Transformer 7.1.10+, TREP Adapter 7.1.3+).

    Example: (RHEL 7) absolute path to an OpenJDK 8 installation directory
    jvm-location /etc/alternatives/java_sdk_1.8.0
    Example: absolute path to the Java installation directory set in the JAVA_HOME environment variable
    jvm-location ${ENV:JAVA_HOME}

The path supplied to jvm-location must follow the path-formatting conventions of the operating system for which the C DataSource binary is compiled:

Operating system Path format Example (truncated)

RHEL

UNIX

jvm-location /etc/alternatives/java_sdk_1.8.0/…​

macOS

UNIX

jvm-location /Library/Java/JavaVirtualMachines/…​

Windows 10

Windows

jvm-location "C:/Program Files/AdoptOpenJDK/…​"

Paths containing spaces should be quoted (see the Windows path above). Windows paths may use forward-slashes as directory separators.

jvm-location and the Deployment Framework

In deployments managed by the Deployment Framework, Caplin Platform blades for Java modules use the Deployment Framework’s built-in configuration variable JVM_LOCATION to set the value of jvm-location:

jvm-location ${JVM_LOCATION}

The default value of JVM_LOCATION is the path to a Java 8 JVM library, derived from the value of the environment variable JAVA_HOME. For deployments that require a Java 11 JVM, use the Deployment Framework’s dfw java command to override the default value of JVM_LOCATION with the absolute path to a Java 11 JVM library:

Example: (RHEL 7) Overriding the default value of JVM_LOCATION with the path to a Java 11 JVM library
$ dfw java /etc/alternatives/java_sdk_11/lib/server/libjvm.so

For detailed information on Caplin Platform compatibility with Java 11, see Caplin Platform System Requirements.

Use in: C

Syntax: jvm-location <path>

Type: string

Default value: [none]

Examples:

  • RHEL 7: jvm-location /etc/alternatives/java_sdk_1.8.0/jre/lib/amd64/server/libjvm.so

  • macOS: jvm-location /Library/Java/JavaVirtualMachines/adoptopenjdk-11.0.2.jdk/Contents/Home/lib/server/libjvm.dylib

  • Windows 10: jvm-location "C:/Program Files/AdoptOpenJDK/jdk-11.0.10.9-hotspot/bin/server/jvm.dll"

jvm-options

jvm-options specifies startup options for a C DataSource application’s embedded JVM. You can specify any of the valid Java command line options.

You can specify multiple options in one instance of jvm-options or use a separate instance of jvm-options per startup option. The two examples below are equivalent.

jvm-options -Xms256m -Xmx256m
jvm-options -Xms256m
jvm-options -Xmx256m

Use in: C

Syntax: jvm-options <java-command-line-options>

Type: array of strings

Default value: [none]

add-javaclass

add-javaclass specifies the main (entry) class of a C DataSource’s Java module. Java modules are used to extend a C DataSource application’s functionality. See, for example, Transformer’s Refiner module.

For examples of how to use add-javaclass within Caplin Platform blades, see:

Use in: C

Syntax:

add-javaclass
   class-id     [string]
   class-name   [string]
   classpath    [array of strings]
end-javaclass
Options
class-id

Type: string | Default: null

A short identifier of the Java class. When the Java module is part of a Java-based Transformer Service blade, class-id must be set to the blade name.

class-name

Type: string | Default: null

The fully-qualified class name of the Java module to load.

classpath

Type: string | Default: null

One or more space-separated Java classpaths that define where the class in class-name is to be loaded from; for example:

classpath %r/lib/java/jmx-child-classloader.jar %r/lib/java/common-jmx.jar

You can have multiple occurrences of classpath in the same add-javaclass item. For example, the classpath above can be rewritten as two classpath options:

classpath %r/lib/java/jmx-child-classloader.jar
classpath %r/lib/java/common-jmx.jar

See also: