Change contract of StubFactory

Instead of an instance method we now use a static supports() method
to determine if a factory matches a given stub type. This is better
for the lifecycle since bean definitions have to be created before
and factory can actually be created and autowired.

It's a slightly unusual contract, but it makes it much harder to
make a mistake with lifecycle, and much easier to install custom
StubFactory instances (as @beans)

Author: dsyer

spring-grpc-core/src/main/java/org/springframework/grpc/client/AbstractStubFactory.java

@@ -23,20 +23,13 @@
 
 public abstract class AbstractStubFactory<T extends AbstractStub<?>> implements StubFactory<T> {
 
-	private final Class<? extends AbstractStub<?>> baseType;
-
-	@SuppressWarnings("unchecked")
-	protected AbstractStubFactory(Class<?> baseType) {
-		this.baseType = (Class<? extends AbstractStub<?>>) baseType;
-	}
-
-	@Override
-	public boolean supports(Class<?> type) {
-		return this.baseType.isAssignableFrom(type);
+	protected static <S extends AbstractStub<?>> boolean supports(Class<S> baseType, Class<?> type) {
+		return baseType.isAssignableFrom(type);
 	}
 
 	@Override
-	public T create(Supplier<ManagedChannel> channel, Class<? extends AbstractStub<?>> type) {
+	public T create(Supplier<ManagedChannel> channel, Class<? extends T> type) {
+		// All the generated stubs are static inner classes of the service
 		Class<?> factory = type.getEnclosingClass();
 		@SuppressWarnings("unchecked")
 		T stub = (T) createStub(channel, factory, methodName());

spring-grpc-core/src/main/java/org/springframework/grpc/client/BlockingStubFactory.java

@@ -15,24 +15,13 @@
  */
 package org.springframework.grpc.client;
 
-import org.springframework.core.Ordered;
-
 import io.grpc.stub.AbstractBlockingStub;
 
-public class BlockingStubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> implements Ordered {
-
-	public BlockingStubFactory() {
-		super(AbstractBlockingStub.class);
-	}
+public class BlockingStubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> {
 
-	@Override
-	public boolean supports(Class<?> type) {
-		return super.supports(type) && !type.getSimpleName().contains("BlockingV2");
-	}
-
-	@Override
-	public int getOrder() {
-		return SimpleStubFactory.SIMPLE_STUB_ORDER - 30;
+	public static boolean supports(Class<?> type) {
+		return AbstractStubFactory.supports(AbstractBlockingStub.class, type)
+				&& !type.getSimpleName().contains("BlockingV2");
 	}
 
 	@Override

spring-grpc-core/src/main/java/org/springframework/grpc/client/BlockingV2StubFactory.java

@@ -15,24 +15,13 @@
  */
 package org.springframework.grpc.client;
 
-import org.springframework.core.Ordered;
-
 import io.grpc.stub.AbstractBlockingStub;
 
-public class BlockingV2StubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> implements Ordered {
-
-	public BlockingV2StubFactory() {
-		super(AbstractBlockingStub.class);
-	}
+public class BlockingV2StubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> {
 
-	@Override
-	public boolean supports(Class<?> type) {
-		return super.supports(type) && type.getSimpleName().contains("BlockingV2");
-	}
-
-	@Override
-	public int getOrder() {
-		return SimpleStubFactory.SIMPLE_STUB_ORDER - 30;
+	public static boolean supports(Class<?> type) {
+		return AbstractStubFactory.supports(AbstractBlockingStub.class, type)
+				&& type.getSimpleName().contains("BlockingV2");
 	}
 
 	@Override

spring-grpc-core/src/main/java/org/springframework/grpc/client/FutureStubFactory.java

@@ -15,20 +15,13 @@
  */
 package org.springframework.grpc.client;
 
-import org.springframework.core.Ordered;
-
 import io.grpc.stub.AbstractBlockingStub;
 import io.grpc.stub.AbstractFutureStub;
 
-public class FutureStubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> implements Ordered {
-
-	public FutureStubFactory() {
-		super(AbstractFutureStub.class);
-	}
+public class FutureStubFactory extends AbstractStubFactory<AbstractBlockingStub<?>> {
 
-	@Override
-	public int getOrder() {
-		return SimpleStubFactory.SIMPLE_STUB_ORDER - 20;
+	public static boolean supports(Class<?> type) {
+		return AbstractStubFactory.supports(AbstractFutureStub.class, type);
 	}
 
 	@Override