Analysis of the core principle of OSGI Service CM framework
OSGI Service CM (Configuration Admin) framework core principle analysis
OSGI (open service gateway initiative) is a Java framework for building a modular, scalable and dynamic deployment system.The OSGI framework manages and configures the configuration information of the component through the Service CM of its core specifications.This article will analyze the core principles of the OSGI Service CM framework and provide the corresponding Java code example.
Framework:
The OSGI Service CM framework provides a unified configuration management mechanism for components in the OSGI environment.Its core idea is to peel the configuration information of the component from the code to achieve the independence and dynamic modification of the configuration.In this way, we can easily modify the behavior of the component through configuration files or other external sources without re -compiling or restarting the entire application.
Core principle:
The core principle of the OSGI Service CM framework is based on two main concepts: Configuration and Managed Service/Factory.
1. Configuration：
Configuration is the basic unit of management component configuration in the OSGI environment.Each Configuration object is associated with a unique PID (lasting identifier) to identify the specific configuration.The configuration information is stored in the form of key value pair, where the key represents the attribute of the configuration item, and the value indicates the value of the configuration item.
2. Managed Service/Factory：
Managed Service/Factory is an OSGI component that implements OSGI components that implement Org.osgi.Service.cm.ManageDService and org.osgi.service.cm.ManageDSAGEDSERVICEFACTORY.These components are registered for OSGI services, and the recovery method provided by the CM framework is called to receive the configuration update notification of the associated PID.
work process:
The following is the basic workflow of the OSGI Service CM framework:
1. Component registration:
When the component starts, it implements the object of the Managed Service/Factory interface as an OSGI service.
2. Configuration creation:
Through the CONFIGURATIONDMIN service of the CM framework, create or obtain the Configuration object related to the component.You can use PID or filter to retrieve the configuration.
3. Configuration release:
Store the configuration information in the Configuration object and publish the configuration update event through the COM framework ConfigurationAdmin service.
4. Configuration update:
When the CM framework is configured, all related Managed Service/Factory components are notified by the callback interface.Components can use the Configuration object to retrieve and analyze the latest configuration information.
5. Dynamic loading configuration:
Change the configuration information at runtime without restart the component.You can dynamically modify the Configuration object through the COM framework ConfigurationAdmin service, and automatically inject the latest configuration into related components.
Example code:
Below is a simple example code to demonstrate how to use the OSGI Service CM framework.
1. Create a Managed Service interface:
import org.osgi.service.cm.ManagedService;
public interface MyManagedService extends ManagedService {
// Define the configuration items that need to be managed
String getMyProperty();
}
2. Implement the managed service interface:
import org.osgi.service.cm.ConfigurationException;
import org.osgi.service.cm.ManagedService;
import java.util.Dictionary;
public class MyManagedServiceImpl implements MyManagedService {
private String myProperty;
@Override
public void updated(Dictionary<String, ?> properties) throws ConfigurationException {
// Analyze the configuration item, and inject the latest configuration information into the component
if (properties != null) {
myProperty = (String) properties.get("my.property");
}
}
public String getMyProperty() {
return myProperty;
}
}
3. Register Managed Service:
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import java.util.Dictionary;
import java.util.Hashtable;
public class Activator implements BundleActivator {
@Override
public void start(BundleContext bundleContext) throws Exception {
// Create and register mymanagedservice
MyManagedService myService = new MyManagedServiceImpl();
Dictionary<String, Object> props = new Hashtable<>();
Props.put ("Service.pid", "My.service.pid"); // Place PID
bundleContext.registerService(MyManagedService.class.getName(), myService, props);
}
@Override
public void stop(BundleContext bundleContext) throws Exception {
// Logging out myManageDservice
// ...
}
}
In the above sample code, we define a configuration item of the component that extended the MyManageDService interface that extended the ManageDService interface.By implementing the update method, we can dynamically adjust the behavior of the component during configuration.Then, we registered MyManageDService as OSGI services in Bundleactivator.
Summarize:
The OSGI Service CM framework is a dynamic configuration management mechanism through decoupling the configuration information and code of the component.This article analyzes its core principles and provides the corresponding Java example code.By using the OSGI Service CM framework, we can easily manage and dynamically modify the configuration of components to improve the flexibility and scalability of the system.
