The @Fallback policy

The @Fallback annotation can only be applied on a method; annotating a class will give an unexpected result:

@Retry(maxRetries = 2)
@Fallback(StringFallbackHandler.class)
public String shouldFallback() {
  ...
}

The fallback method is called after the number of retries is reached. In the previous example, the method will be retried twice in case of an error, and then the fallback will be used to invoke another piece of code—in this case, the following StringFallbackHandler class:

import javax.enterprise.context.ApplicationScoped;

import org.eclipse.microprofile.config.inject.ConfigProperty;
import org.eclipse.microprofile.faulttolerance.ExecutionContext;
import org.eclipse.microprofile.faulttolerance.FallbackHandler;

@ApplicationScoped
public class StringFallbackHandler implements FallbackHandler<String> {
    @ConfigProperty(name="app1.requestFallbackReply", defaultValue = "Unconfigured Default Reply")
    private String replyString;

    @Override
    public String handle(ExecutionContext ec) {
        return replyString;
    }
}

Fallback code can be defined by a class implementing the FallbackHandler interface (see the previous code) or by a method in the current bean. In the StringFallbackHandler code, a MicroProfile Config property named app1.requestFallbackReply is used to externalize the application's fallback string value.