Configuration

The iKnowBase web application can be configured to adapt to different needs using configuration properties.

Overview

First, modules in iKnowBase expose a number of Configuration objects that control the workings of the module. Each configuration object has one or more named configuration properties that can be set by the user. If the user does not set a given configuration property, a default value will be used.

When the iknowbase web application starts, it populates the configuration objects with property values set by the user, and then uses the configuration objects to adapt the module. Note that this implies that making changes to properties will require a restart of the application server.

At run time, the actual property values can be inspected in the management console, e.g. at /ikb$console.

Property sources

Configuration properties are available from many different sources. When an application requires a property value, it will check these sources in order, and the first one that can supply the required property will be used:

• The property source “IKB_INSTALLATION_PROPERTIES” represents values loaded from the database table _ikb_installation_properties_.
• The property source “servletConfigInitParams” is typically not used, but is provided as a standard source by the underlying technology.
• The property source “servletContextInitParams” is typically not used, but is provided as a standard source by the underlying technology.
• The property source “jndiProperties” is typically not used, but is provided as a standard source by the underlying technology.
• The property source “systemProperties” gets values from the command line used to start the java virtual machine, so that you can directly specify property values when starting the server.
• The property source “systemEnvironment” gets values from the operating system environment (where you find e.g. the PATH environment variable)

In practice, you will probably use either java system properties or the ikb_installation_properties tables:

• Java system properties are easy to set, in particular in an installation with a single application server instance
• The ikb_installation_properties database table is more easily managed, and allows you to set values that apply to multiple application server instances

System properties

System properties is the “standard” java mechanism for configuring an application. They may be set in various ways:

• Using “-Dname=value” as a command-line option to the java program
• Using “System.name=value” in an iKnowBase property file

Thus, to enable the activiti process engine inside iKnowBase, you could use the following iKnowBase property file:

db.URL = jdbc:oracle:thin:@//localhost:1521/orcl
db.ikbUser = ikb_prod
db.ikbPassword = SECRETPASSWORD

System.com.iknowbase.process.activiti.enabled=true

The ikb_installation_properties database table

Using the IKB_INSTALLATION_PROPERTY table is the most common option. Since this table is shared between all applications and all application server instances, it is possible to add expressions that are checked at runtime in order to select the proper property. This is done using the “instance_qualifier” table column.

At startup, each iKnowBase java web application loads properties from the ikb_installation_table. For each row, it will evaluate the “instance_qualifier” value to decide if this particular property is valid for this particular application instance. The qualifier is interpreted using the Spring Expression Language, which allows for combining various types of tests.

The available variables and methods for the expression is limited to the following logical interface definition:

These can be combined in several ways, to achieve various effects: