The Properties interface provides the following operations for reading property values:
string getProperty(string key)
This operation returns the value of the specified property. If the property is not set, the operation returns the empty string.
string getPropertyWithDefault(string key, string value)
This operation returns the value of the specified property. If the property is not set, the operation returns the supplied default value.
int getPropertyAsInt(string key)
This operation returns the value of the specified property as an integer. If the property is not set or contains a string that does not parse as an integer, the operation returns zero.
int getPropertyAsIntWithDefault(string key, int value)
This operation returns the value of the specified property as an integer. If the property is not set or contains a string that does not parse as an integer, the operation returns the supplied default value.
PropertyDict getPropertiesForPrefix(string prefix)
This operation returns all properties that begin with the specified prefix as a dictionary of typePropertyDict. This operation is useful if you want to extract the properties for a specific subsystem. For example,
getPropertiesForPrefix("Filesystem")
returns all properties that start with the prefixFilesystem, such asFilesystem.MaxFileSize. You can then use the usual dictionary lookup operations to extract the properties of interest from the returned dictionary.
With these operations, using application-specific properties now becomes the simple matter of initializing a communicator as usual, getting access to the communicator's properties, and examining the desired property value. For example:
// ...
Ice::CommunicatorPtr ic;
// ...
ic = Ice::initialize(argc, argv);
// Get the maximum file size.
//
Ice::PropertiesPtr props = ic->getProperties();
Ice::Int maxSize = props->getPropertyAsIntWithDefault("Filesystem.MaxFileSize", 1024);
// ...
Assuming that you have created a configuration file that sets the Filesystem.MaxFileSize property (and that you have set the ICE_CONFIG variable or the --Ice.Config option accordingly), your application will pick up the configured value of the property.
The technique shown above allows you to obtain application-specific properties from a configuration file. If you also want the ability to set application-specific properties on the command line, you will need to parse command-line options for your prefix. (Calling initialize to create a communicator only parses those command line options having a reserved prefix.)