# Preference Settings¶

When you run Phoebus, you may find that it cannot connect to your control system because for example the EPICS Channel Access address list is not configured.

To locate available preferences, refer to the complete Preferences Listing or check the source code for files named *preferences.properties, for example in the core-pv sources:

# ----------------------------------------
# Package org.phoebus.applications.pvtable
# ----------------------------------------

# Show a "Description" column that reads xxx.DESC?
show_description=true

# -------------------------
# Package org.phoebus.pv.ca
# -------------------------



Create a file settings.ini that lists the settings you want to change:

# Format:
#
#  package_name/setting=value


The value might be plain text, with details depending on the preference setting, for example allowing an IP address for the addr_list or a true value for some boolean preference setting. In addition, Java properties or environment variables can be used like this:

# Example of using a Java property 'gateway'.
# If it is set to 'my_ca_gateway.site.org:5066',
# this example would have the same end result as
# the previous example.
#
# If no Java property 'gateway' is found,
# an environment variable 'gateway' is checked.


Start Phoebus like this to import the settings from your file:

phoebus.sh -settings /path/to/settings.ini


Start Phoebus like this to import the settings from a remote URL:

phoebus.sh -settings http://mysite.com/settings.ini


Loading from URL assumes remote service does not respond with a redirect. Moreover, if using https, the remote URL must be backed by a trusted certificate.

At runtime, you can view the currently effective preference settings from the menu Help, About. The Details pane includes a tab that lists all preference settings in the same format that is used by the settings.ini file. You can copy settings that you need to change from the display into your settings file.

The same details pane that lists current preference settings also offers an Import Preferences button for loading a settings.ini file. You may use that as an alternative to the command line -settings .. option, but note that settings loaded via this button only become effective after a restart.

Settings loaded via either the -settings .. command line option or the Import Preferences button are stored in the user location (see Locations). They remain effective until different settings are loaded or the user location is deleted. It is therefore not necessary to always run the application with the same -settings .. command line option. Just invoking with the command line option once or using the Import Preferences button once suffices to load settings. In practice, however, it is advisable to include the -settings .. command line option in a site-specific application start script. This way, new users do not need to remember to once start with the option, and existing users will benefit from changes to the settings file.

Conceptually, preference settings are meant to hold critical configuration parameters like the control system network configuration. They are configured by system administrators, and once they are properly adjusted for your site, there is usually no need to change them.

Most important, these are not settings that an end user would need to see and frequently adjust during ordinary use of the application. For such runtime settings, each application needs to offer user interface options like context menus or configuration dialogs.

When you package phoebus for distribution at your site, you can also place a file settings.ini in the installation location (see Locations). At startup, Phoebus will automatically load the file settings.ini from the installation location, eliminating the need for your users to add the -settings .. command line option.

## Developer Notes¶

In your code, create a file with a name that ends in *preferences.properties. In that file, list the available settings, with explanatory comments:

# ---------------------------------------
# Package org.phoebus.applications.my_app
# ---------------------------------------

# Note that the above
#
#    "# Package name.of.your.package"
#
# and users will need to know the package name to
# assemble their settings file.

# Explain what each setting means,
# what values are allowed etc.
my_setting=SomeValue

# Enable some feature, allowed values are true or false
my_other_setting=true


In your application code, you can most conveniently access them like this:

package org.phoebus.applications.my_app

import org.phoebus.framework.preferences.AnnotatedPreferences;
import org.phoebus.framework.preferences.Preference;

class MyAppSettings
{
@Preference public static String my_setting;
@Preference public static boolean my_other_setting;

static
{
AnnotatedPreferences.initialize(MyAppSettings.class, "/my_app_preferences.properties");
}
}


The AnnotatedPreferences helper will read your *preferences.properties, apply updates from java.util.prefs.Preferences, and then set the values of all static fields annotated with @Preference. It handles basic types like int, long, double, boolean, String, File. It can also parse comma-separated items into int[] or String[].

By default, it uses the name of the field as the name of the preference setting, which can be overridden via @Preference(name="name_of_settings"). If more elaborate settings need to be handled, AnnotatedPreferences.initialize returns a PreferencesReader, or you could directly use that lower level API like this:

package org.phoebus.applications.my_app

# The class that you pass here determines the package name for your preferences

String pref1 = prefs.get("my_setting");
Boolean pref2 = prefs.getBoolean("my_other_setting");
// .. use getInt, getDouble as needed.
// For more complex settings, use get() to fetch the string
// and parse as desired.


The PreferencesReader loads defaults from the property file, then allows overrides via the java.util.prefs.Preferences API. By default, the user settings are stored in a .phoebus folder in the home directory. This location can be changed by setting the Java property phoebus.user.

In the future, a preference UI might be added, but as mentioned the preference settings are not meant to be adjusted by end users.