Apache Felix Inventory Printer
The Apache Felix Inventory Printer is a simple and extensible framework to retrieve inventory information about applications running in an OSGi Framework. Typical information includes currently installed bundles, their state, available configurations, framework properties, log files etc.
Historically the Inventory Printer evolved from the Web Console Configuration Printer framework.
Introduction
When trying to find a problem or analyzing the system it would be nice to have a single place to go to and get available information. The Apache Felix inventory bundle tries to exactly fill this gap.
Originally, the idea started within the Apache Felix WebConsole and it’s configuration printers - these pluggable printers allowed to view all available status information in a web browser or download this as zip file. While this already solves most use cases, tying this general functionality to a web console felt wrong, and that’s when the inventory module started.
The current version of the inventory implementation, registers all available InventoryPrinters (see below) as plugins to the web console as this is still the number one use case.
Requirements
In and of itself the Apache Felix Inventory Printer module is independent of other modules.
To actually get access to the output of Inventory Printer services, though, the Apache Felix Web Console must be installed.
In the future Integration with the Apache Felix Gogo Shell will also be provided in which case the Apache Felix Gogo Shell must be installed.
Inventory Printer Services
Inventory Printer Services are registered as org.apache.felix.inventory.InventoryPrinter type OSGi services with the following service registration properties:
| Property | Default Value | Description |
|---|---|---|
|
— |
The unique name of the printer. If there are two or more services with the same name, the service with the highest ranking is used. |
|
— |
The title displayed by tools when this printer is used. It should be descriptive but short. |
|
— |
The property defining the supported rendering formats.
The value of this property is either a string or a string array containing valid names of |
|
|
Optional property controlling whether the printer will be displayed in the web console. By default, a printer is displayed in the web console, unless this property is added with the value 'false'. The property value can either be a boolean or a string. |
The first three properties are required for the Inventory Printer service to be accepted. Otherwise the service is ignored by the framework printing a message to the log.
To prevent bundle resolution failure if the InventoryPrinter API is not available in the framework it is suggested to register the Inventory Printer services as service factories and dynamically import the API.
See the question How to provide optional services? in the Apache Felix OSGi FAQ for more details.
Example Inventory Printer Service
@Component
@Service
@Properties({
@Property(name = "felix.inventory.printer.name", value = "sample"),
@Property(name = "felix.inventory.printer.title", value = "This is a Sample"),
@Property(name = "felix.inventory.printer.format",
value = { "TEXT", "HTML", "JSON" })
})
public class SampleInvetoryPrinter implements InventoryPrinter
{
public void print(PrintWriter printWriter, Format format, boolean isZip)
{
if (format == Format.JSON)
{
printWriter.print("{ \"key\": \"Sample Output\" }");
}
else if (format == Format.HTML)
{
printWriter.print("<b>Sample Output</b>");
}
else
{
printWriter.print("Sample Output");
}
}
}See also the API JavaDoc.
ZIP Attachment Provider
If an Inventory Printer wants to provide additional contents to an Inventory ZIP File, it can implement the ZipAttachmentProvider interface and provide additional files when the zip is created.
Configuration Printer Services
For backwards compatibility the Inventory Printer framework also supports legacy Apache Felix Web Console ConfigurationPrinter services.
Configuration Printer services are wrapped in an InventoryPrinter adapter and re-registered as Inventory Printer services.
Thus they are registered with the Web Console or the Gogo Shell as if the Configuration Printer would be an Inventory Printer.
Configuration Printer Services are registered as org.apache.felix.webconsole.ConfigurationPrinter type OSGi services with the following service registration properties:
| Property | Default Value | Description |
|---|---|---|
|
— |
The title under which to display the Configuration Printer |
|
— |
The Configuration Printer modes supported.
This may be one or more of the values |
|
— |
Deprecated synonym for the |
|
|
Property indicating whether output generated in |
Integration with the Apache Felix Web Console
The Inventory Printer framework has first class integration with the Apache Felix Web Console.
Each InventoryPrinter service is registered as a plugin in the Inventory category of the Web Console.
To prevent an Invetory Printer from being registered in the Web Console, the felix.inventory.printer.webconsole service registration property must be set to false.
Integration with the Apache Felix Gogo Shell
Gogo Shell integration is not implemented in the first version of the Apache Felix Inventory Printer module.
Issues
Should you have any questions using the Inventory Printer, please send a note to one of our link:{{ refs.mailinglists.path }}[Mailing Lists].
Please report any issues with the Inventory Printer in our issue tracking system (JIRA) and be sure to report for the Inventory component. See our link:{{ refs.issue-tracking.path }}[Issue Tracking] page for more details.