The ability to configure an application’s properties externally provides a great deal of flexibility: you can use any combination of command-line options and configuration files to achieve the desired settings, all without having to modify your application. This section describes two ways of loading property settings from a file.
The Ice run time automatically loads a configuration file during the creation of a property set, which is an instance of the
Ice::Properties interface. Every communicator has its own property set from which it derives its configuration. If an application does not supply a property set when it calls
Ice::initialize (or the equivalent in other language mappings), the Ice run time internally creates a property set for the new communicator.
Note however that Ice loads a configuration file automatically only when the application creates a property set using an argument vector. This occurs when the application passes an argument vector to create a property set explicitly (as discussed in
Section 30.9), or when the application passes an argument vector to
Ice::initialize.
Ice automatically loads the contents of the configuration file named in the ICE_CONFIG environment variable (assuming the prerequisites described in
Section 30.5.1 are met). For example:
If you use the ICE_CONFIG environment variable together with command-line options for other properties, the settings on the command line override the settings in the configuration file. For example:
This sets the value of the Ice.MessageSizeMax property to
4096 regardless of any setting of this property in
/usr/local/filesystem/config.
This causes property settings to be retrieved from /usr/local/filesystem/config, followed by any settings in the file
config in the current directory; settings in
./config override settings
/usr/local/filesystem/config.
The Ice.Config property has special meaning to the Ice run time: it determines the path name of a configuration file from which to read property settings. For example:
The ‑‑Ice.Config command-line option overrides any setting of the
ICE_CONFIG environment variable, that is, if the
ICE_CONFIG environment variable is set and you also use the
‑‑Ice.Config command-line option, the configuration file specified by the
ICE_CONFIG environment variable is ignored.
If you use the ‑‑Ice.Config command-line option together with settings for other properties, the settings on the command line override the settings in the configuration file. For example:
This sets the value of the Ice.MessageSizeMax property to
4096 regardless of any setting of this property in
/usr/local/filesystem/config. The placement of the
‑‑Ice.Config option on the command line has no influence on this precedence. For example, the following command is equivalent to the preceding one:
Settings of the Ice.Config property inside a configuration file are ignored, that is, you can set
Ice.Config only on the command line.
If you use the ‑‑Ice.Config option more than once, only the last setting of the option is used and the preceding ones are ignored. For example:
This causes property settings to be retrieved from /usr/local/filesystem/config, followed by any settings in the file
config in the current directory; settings in
./config override settings
/usr/local/filesystem/config.
