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FallbackFactory.java
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69 lines (60 loc) · 1.87 KB
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package feign.hystrix;
import feign.FeignException;
import java.util.logging.Level;
import java.util.logging.Logger;
import static feign.Util.checkNotNull;
/**
* Used to control the fallback given its cause.
*
* Ex.
* <pre>{@code
* // This instance will be invoked if there are errors of any kind.
* FallbackFactory<GitHub> fallbackFactory = cause -> (owner, repo) -> {
* if (cause instanceof FeignException && ((FeignException) cause).status() == 403) {
* return Collections.emptyList();
* } else {
* return Arrays.asList("yogi");
* }
* };
*
* GitHub github = HystrixFeign.builder()
* ...
* .target(GitHub.class, "https://api.github.com", fallbackFactory);
* }
* </pre>
*
* @param <T> the feign interface type
*/
public interface FallbackFactory<T> {
/**
* Returns an instance of the fallback appropriate for the given cause
*
* @param cause corresponds to {@link com.netflix.hystrix.AbstractCommand#getExecutionException()}
* often, but not always an instance of {@link FeignException}.
*/
T create(Throwable cause);
/** Returns a constant fallback after logging the cause to FINE level. */
final class Default<T> implements FallbackFactory<T> {
// jul to not add a dependency
final Logger logger;
final T constant;
public Default(T constant) {
this(constant, Logger.getLogger(Default.class.getName()));
}
Default(T constant, Logger logger) {
this.constant = checkNotNull(constant, "fallback");
this.logger = checkNotNull(logger, "logger");
}
@Override
public T create(Throwable cause) {
if (logger.isLoggable(Level.FINE)) {
logger.log(Level.FINE, "fallback due to: " + cause.getMessage(), cause);
}
return constant;
}
@Override
public String toString() {
return constant.toString();
}
}
}