A PrefixConfig gives PrefixedProperties an hint which prefixes are valid for a specific environment and which are not. PrefixConfigs prevent PrefixedProperties from "learning" new prefixes on the fly. Well there is one excuse but that will be discussed later on.
First of all a PrefixConfig is more or less a list of possible prefixes of an environment. For example The StagingPrefixConfig class is a predefined configuration for "local", "development", "test", "integration", "qa", "prelive", "live" environment.
To create your own StageConfig you might just create a subclass of DefaultPrefixConfig and set all prefixes within the constructor.
The following example will show you a PrefixConfig for three services. You can use a PrefixConfig on standalone basis or use it for cascading prefixes.
public class ServicePrefixConfig extends DefaultPrefixConfig {
private static final long serialVersionUID = 1L;
public final static String PRODUCT_SRV = "prdsrv";
public final static String ACCOUNTING_SRV = "accsrv";
public final static String DELIVERY_SRV = "delsrv";
private final static String[] SERVICES = { PRODUCT_SRV, ACCOUNTING_SRV, DELIVERY_SRV };
public ServicePrefixConfig() {
super(ServicePrefixConfig.SERVICES);
}
/** Will set the defaultConfig for this environment */
public ServicePrefixConfig(final String prefix) {
super(ServicePrefixConfig.SERVICES, prefix);
}
}
Use the PrefixConfig just like a normal prefixConfiguration:
PrefixedProperties properties = new PrefixedProperties( new ServicePrefixConfig("prdsrv") );
or set the PrefixConfig afterwards:
PrefixedProperties properties = new PrefixedProperties();
properties.setPrefixConfig( new ServicePrefixConfig("prdsrv") ); //this will remove a prior set PrefixConfig and also the configured prefix.
With PrefixConfigs it is also possible to use cascading environments a sub-environment could be a department or group, hosts, services, components, users and many more.
A cascading prefixed property could look like: stage.department.group.host.service.component.key=someValue and you could also define defaults by excluding prefixes: department.service.key=somedefaultValue, group.key=another default
The most specific key will be returned.
To define cascading PrefixedProperties with PrefixConfigs you can do it in the following way:
PrefixedProperties properties = PrefixedProperties.createCascadingPrefixProperties(new StagingPrefixConfig("test"), new ServicePrefixConfig("prdsrv"));
To change the configuration you can now use the setDefaultPrefix in the following ways:
properties.setDefaultPrefix("liv"); //changes from test to live
properties.setDefaultPrefix("delsrv"); //changes from production service to delivery service
properties.setDefaultPrefix("qa.accsrv"); //changes to quality assurance and accounting service
You can also combine the "learning" feature and PrefixConfigurations. For that you can use the DynamicPrefixConfig together with other prefix configurations.
PrefixedProperties properties = PrefixedProperties.createCascadingPrefixProperties(new StagingPrefixConfig("test"),
new ServicePrefixConfig("prdsrv"), new DynamicPrefixConfig() );
properties.setDefaultPrefix("qa.accsrv.dynamic");
Another example with property retrieval:
//ServicePrefixConfig consists of deliverysrv, accountingsrv, productsrv
//ComponentPrefixConfig consists of database
PrefixedProperties properties = PrefixedProperties.createCascadingPrefixProperties(new StagingPrefixConfig(), new ServicePrefixConfig(), new ComponentPrefixConfig());
//setup the properties
properties.setConfiguredPrefix("liv.deliverysrv.database);
properties.setProperty("liv.connections", "10");
properties.setProperty("liv.deliverysrv.database.connections", "20");
properties.setProperty("accountingsrv.connections", "30");//will work for all stages
properties.get("connections"); //will return 20
properties.setConfiguredPrefix("productsrv");//just changes the service configuration not the stage or component
properties.get("connections"); //will return 10 by using the liv.connections fallback
properties.setConfiguredPrefix("accountingsrv");//changes the service configuration again.
properties.get("connections"); //will return 30
To change or reset the prefixConfig you can use the * sign to clear all configuredPrefixes or defaultPrefixes.
Clearing the configuredPrefixes will make all requests for an property fallback to the defaultPrefixes. You can do that via the PrefixConfig itself by calling setPrefix(String prefix), or use the setConfiguredPrefix(String) on the PrefixedProperties class. If you use cascading properties like in the example above, you can use setConfiguredPrefix("..") to remove all three configured prefixes from the PrefixConfigs. Or setConfiguredPrefix("test..") to set the first config to test and clear the other two configs. To clear all configurations you can also use setConfiguredPrefix("*") as a shortcut. Please note that the wildcard can be used as a standalone only don't try to mix it up like setConfiguredPrefix("test.*") it wouldn't work.
The same mechanism works for clearing the defaults. Either by using ConfiguredPrefix directly or use setDefaultPrefix(String)