RESTEasy 3.12.0.Final: MicroProfile Config

By Ron Sigal | May 18, 2020

RESTEasy 3.12.0.Final, just released, will ship with the upcoming WildFly 20. Besides a number of bug fixes, it has one new feature, the incorporation of MicroProfile Config. Previously, RESTEasy configuration parameters were retrieved from web.xml context-params and init-params. Now, as long as the necessary MicroProfile API and implementation jars are present (see Section “Configuring MicroProfile Config” of the RESTEasy User Guide) are available, all parameters are retrieved by way of an org.eclipse.microprofile.config.Config. A Config represents any number of org.eclipse.microprofile.config.spi.ConfigSources, each of which is a map of parameters to values. There are several ConfigSources required by the MicroProfile Config spec, including one for system properties and one for environment variables. To those, RESTEasy adds ConfigSources for web.xml context-params, servlet init-params, and filter init-params. Any of these can be used to retrieve RESTEASY parameters such as “resteasy.servlet.mapping.prefix” and “”.

Each ConfigSource has an associated priority. For example, the system property ConfigSource has a higher priority than the environment variable ConfigSource so, if a given parameter is defined as both a system property and an environment variable, the value in the system property will be used. Similarly, a servlet init-param will take precedence over a context-param.

If the necessary jars are not in the environment, RESTEasy 3.12.0.Final falls back to the previous method of examining web.xml parameters.

Of particular interest to the JAX-RS developer is the fact that, if the necessary MicroProfile API and implementation jars are present, the same Config mechanism can be used in application code. For example,

Config config = ConfigProvider.getConfig();
Optional<String> opt = config.getOptionalValue("param", String.class);
String param = opt.orElse("d'oh");

For release notes, see RESTEasy 3.12.0.Final