codes.sf.springboot.grpc.client.GrpcChannelSource Maven / Gradle / Ivy
package codes.sf.springboot.grpc.client;
import io.grpc.Channel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.stub.AbstractStub;
/**
* A strategy interface for resolving {@linkplain Channel Channels} for gRPC stubs.
*
* GrpcChannelSource is usually where your service discovery logic
* goes. It is the place where you map the client stubs to their server
* implementations.
*
*
Auto configuration will autodetect the GrpcChannelSource bean and
* use it to resolve channels for new gRPC stub instances. In other words
* you may register your GrpcChannelSource as a simple {@code @Bean} in
* your {@code @Configuration} classes.
*
*
Note that there must be at most one GrpcChannelSource in the
* ApplicationContext, otherwise you'll get an error.
*
*
If no GrpcChannelSource is found in the ApplicationContext, auto
* configuration will
*
* -
* first look for a {@link Channel} in the ApplicationContext to use instead;
*
* -
* if no channel bean is found, it will configure a new
* {@linkplain ManagedChannelBuilder#usePlaintext() plaintext} one
* with target from environment property {@code grpc.client.target};
*
* -
* finally if no property is found, it will default to creating a new
* plaintext channel bean with target "{@code localhost:6565}"
*
*
*
* If you're creating a GrpcChannelSource that returns a constant channel,
* consider using convenience function {@link #of(Channel) GrpcChannelSource.of(Channel)}
*
* @author Semyon Fishman
* @since 0.0.1
*/
@FunctionalInterface
public interface GrpcChannelSource {
/**
* Resolve channel for stub type.
*
* @param stubClass the stub type
* @return resolved channel, may not be {@code null}
*/
Channel resolve(Class> stubClass);
/**
* Convenience method for build GrpcChannelSource that returns
* a constant channel instance.
*
* @param channel the constant channel instance to return
* @return newly constructed GrpcChannelSource
*/
static GrpcChannelSource of(Channel channel) {
return stubClass -> channel;
}
}