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RESTX Settings support

Restx provides a simple yet powerful way to handle your application settings.

Defining a settings interface

First you need to define an interface which will be used to access your application or module settings:

public interface MySettings {
    @SettingsKey(key = "example.key1")
    String key1();
    @SettingsKey(key = "example.key2", defaultValue = "MyValue2")
    String key2();
    @SettingsKey(key = "example.key3", defaultValue = "MyValue3",
            doc = "This is an example key 3")
    String key3();

Each method defines a settings key, i.e. a particular setting. You can provide a default value for each setting. The doc parameter allow to add some basic documentation for the setting, which will be displayed in the admin page for the settings.

Using the settings

Then you can simply get an instance of this interface injected in any of your components:

public class MyComponent {
    public MyComponent(MySettings settings) {
        System.out.println(String.format("I got these settings:\n" +
                " key1: %s ; key2: %s ; key3: %s",

Note that all settings are also made available as Named strings in the factory, so you can get a single setting injected:

public class MyComponent {
    public MyComponent(@Named("example.key1") key1) {

Providing the settings

You have several way to define the value of the settings:

Using default value

By giving a default value in the settings key, you can define the value the setting will take by default

Using properties file

You can easily load settings values from a properties file. Restx provide a ConfigLoader component which can be used to load such properties from classpath:

public class MyModule {
  public ConfigSupplier myConfigSupplier(ConfigLoader configLoader) {
        return configLoader.fromResource("myapp/myConfig");

This will try to load settings from to classpath resources:

  • myapp/myConfig.[env].properties
  • myapp/

where [env] is the value of a string named ‘env’ (which can be set using system property).

The properties file are not true properties file, they have the following differences:

  • use UTF-8 encoding
  • lines beginning with # are considered to be the documentation of the key following the comment

Here is an example file:

# this is the doc for key1
# which can be on multiple lines

If you want to take advantage of this properties format but don’t want to load it from the classpath, you can also use the parser on its own:

    public ConfigSupplier myConfigSupplier() {
        return new ConfigSupplier() {
            public RestxConfig get() {
                try {
                    return StdRestxConfig.parse("", 
                            Files.newReaderSupplier(new File(""), Charsets.UTF_8));
                } catch (IOException e) {
                    throw new RuntimeException(e);

Using named strings

You can provide a named string in the factory to set the value of a setting.

For instance:

public class MyModule {
  @Provides @Named("example.key1") public String thisKey() { return "myvalue"; }

This is useful if you want to do programmatic settings.

Using system properties

System properties set using -Dexample.key1=value will override the value of the setting.

Web Console

You can access all the settings values in the admin console, on /@/ui/config/.

Settings console

As you can see the console provides:

  • the origin of each value (in the screenshot, key2 was set with system property, key1 in a properties file in classpath, and key3 used the default value from the rxinvoice.MySettings interface)
  • the documentation for the key, coming either from the settings interface or from the properties file.