io.smallrye.reactive.messaging.MessageConverter Maven / Gradle / Ivy
package io.smallrye.reactive.messaging;
import java.lang.reflect.Type;
import jakarta.enterprise.inject.spi.Prioritized;
import org.eclipse.microprofile.reactive.messaging.Message;
import io.smallrye.common.annotation.Experimental;
/**
* Converter transforming {@code Message} into {@code Message}.
* To register a converter, expose a, generally {@code ApplicationScoped} bean, implementing this interface.
*
* When multiple converters are available, implementation should override the {@link #getPriority()} method.
* Converters with higher priority (lesser value) are executed first.
* The default priority is {@link #CONVERTER_DEFAULT_PRIORITY}.
*/
@Experimental("SmallRye only feature")
public interface MessageConverter extends Prioritized {
/**
* Default priority: {@code 100}
*/
int CONVERTER_DEFAULT_PRIORITY = 100;
/**
* Checks whether this instance of converter can convert the given message {@code in} into a {@code Message} with
* {@code T} being the type represented by {@code target}.
*
* When reactive messaging looks for a converter, it picks the first converter returning {@code true} for a given
* message.
*
* @param in the input message, not {@code null}
* @param target the target type, generally the type ingested by a method
* @return {@code true} if the conversion is possible, {@code false} otherwise.
*/
boolean canConvert(Message in, Type target);
/**
* Converts the given message {@code in} into a {@code Message}.
* This method is only called after a successful call to {@link #canConvert(Message, Type)} with the given target type.
*
* @param in the input message
* @param target the target type
* @return the converted message.
*/
Message convert(Message in, Type target);
@Override
default int getPriority() {
return CONVERTER_DEFAULT_PRIORITY;
}
class IdentityConverter implements MessageConverter {
public static final IdentityConverter INSTANCE = new IdentityConverter();
private IdentityConverter() {
// Avoid direct instantiation.
}
@Override
public boolean canConvert(Message in, Type target) {
return true;
}
@Override
public Message convert(Message in, Type target) {
return in;
}
}
}