Modify default channel factory to add support for 'null' schemes

Fixes #419

Author: ST-DDT

docs/en/client/configuration.md

@@ -76,6 +76,11 @@ There are a number of supported schemes, that you can use to determine the targe
   This is a special scheme that will bypass the normal channel factory and will use the `InProcessChannelFactory`
   instead. Use it to connect to the [`InProcessServer`](../server/configuration.md#enabling-the-inprocessserver). \
   Example: `in-process:foobar`
+- `null`: \
+  This is a special scheme that will bypass the normal channel factory and will use the `NullChannelFactory`
+  instead. Use it to use `null` for a GrpcClient annotated field. \
+  Useful for testing. \
+  Example: `null:/`
 - *custom*: \
   You can define custom
   [`NameResolverProvider`s](https://javadoc.io/page/io.grpc/grpc-all/latest/io/grpc/NameResolverProvider.html) those

docs/en/client/testing.md

@@ -11,6 +11,7 @@ This section describes how you write tests for components that use the `@GrpcCli
 - [Useful Dependencies](#useful-dependencies)
 - [Using a Mocked Stub](#using-a-mocked-stub)
 - [Running a Dummy Server](#running-a-dummy-server)
+- [Skipping injection](#skipping-injection)
 
 ## Additional Topics <!-- omit in toc -->
 
@@ -254,6 +255,31 @@ public class ChatServiceImplForMyComponentIntegrationTest extends ChatServiceGrp
 }
 ````
 
+## Skipping injection
+
+If you don't need a specific `@GrpcClient` in a test, then you can configure it to be skipped using the `null` scheme.
+(In that case it will be injected with `null`)
+
+````java
+@SpringBootTest(properties = {
+        "grpc.client.test.address=null:/",
+}, ...)
+class MyTest {
+
+    @GrpcClient("test")
+    Channel channel;
+
+    @Test()
+    void test() {
+        assertNull(channel);
+    }
+
+}
+````
+
+> **Note:** Due to configuration limitations you cannot use just `null` or `null:` as address,
+> you have to specify a scheme specific part e.g.: `null:/` or `null:null`.
+
 ## Additional Topics <!-- omit in toc -->
 
 - [Getting Started](getting-started.md)

grpc-client-spring-boot-autoconfigure/src/main/java/net/devh/boot/grpc/client/autoconfigure/GrpcClientAutoConfiguration.java

@@ -39,8 +39,9 @@
 import net.devh.boot.grpc.client.channelfactory.GrpcChannelConfigurer;
 import net.devh.boot.grpc.client.channelfactory.GrpcChannelFactory;
 import net.devh.boot.grpc.client.channelfactory.InProcessChannelFactory;
-import net.devh.boot.grpc.client.channelfactory.InProcessOrAlternativeChannelFactory;
 import net.devh.boot.grpc.client.channelfactory.NettyChannelFactory;
+import net.devh.boot.grpc.client.channelfactory.NullChannelFactory;
+import net.devh.boot.grpc.client.channelfactory.SchemaAwareChannelFactory;
 import net.devh.boot.grpc.client.channelfactory.ShadedNettyChannelFactory;
 import net.devh.boot.grpc.client.config.GrpcChannelsProperties;
 import net.devh.boot.grpc.client.inject.GrpcClientBeanPostProcessor;
@@ -139,6 +140,7 @@ List<GrpcChannelConfigurer> defaultChannelConfigurers() {
     }
 
     // First try the shaded netty channel factory
+    @SuppressWarnings("resource")
     @ConditionalOnMissingBean(GrpcChannelFactory.class)
     @ConditionalOnClass(name = {"io.grpc.netty.shaded.io.netty.channel.Channel",
             "io.grpc.netty.shaded.io.grpc.netty.NettyChannelBuilder"})
@@ -152,12 +154,15 @@ GrpcChannelFactory shadedNettyGrpcChannelFactory(
         log.info("Detected grpc-netty-shaded: Creating ShadedNettyChannelFactory + InProcessChannelFactory");
         final ShadedNettyChannelFactory channelFactory =
                 new ShadedNettyChannelFactory(properties, globalClientInterceptorRegistry, channelConfigurers);
-        final InProcessChannelFactory inProcessChannelFactory =
+        final InProcessChannelFactory inProcess =
                 new InProcessChannelFactory(properties, globalClientInterceptorRegistry, channelConfigurers);
-        return new InProcessOrAlternativeChannelFactory(properties, inProcessChannelFactory, channelFactory);
+        return new SchemaAwareChannelFactory(properties, channelFactory)
+                .put(InProcessChannelFactory.SCHEME, inProcess)
+                .put(NullChannelFactory.SCHEME, new NullChannelFactory());
     }
 
     // Then try the normal netty channel factory
+    @SuppressWarnings("resource")
     @ConditionalOnMissingBean(GrpcChannelFactory.class)
     @ConditionalOnClass(name = {"io.netty.channel.Channel", "io.grpc.netty.NettyChannelBuilder"})
     @Bean
@@ -170,9 +175,11 @@ GrpcChannelFactory nettyGrpcChannelFactory(
         log.info("Detected grpc-netty: Creating NettyChannelFactory + InProcessChannelFactory");
         final NettyChannelFactory channelFactory =
                 new NettyChannelFactory(properties, globalClientInterceptorRegistry, channelConfigurers);
-        final InProcessChannelFactory inProcessChannelFactory =
+        final InProcessChannelFactory inProcess =
                 new InProcessChannelFactory(properties, globalClientInterceptorRegistry, channelConfigurers);
-        return new InProcessOrAlternativeChannelFactory(properties, inProcessChannelFactory, channelFactory);
+        return new SchemaAwareChannelFactory(properties, channelFactory)
+                .put(InProcessChannelFactory.SCHEME, inProcess)
+                .put(NullChannelFactory.SCHEME, new NullChannelFactory());
     }
 
     // Finally try the in process channel factory

grpc-client-spring-boot-autoconfigure/src/main/java/net/devh/boot/grpc/client/channelfactory/GrpcChannelFactory.java

@@ -45,7 +45,8 @@ public interface GrpcChannelFactory extends AutoCloseable {
      * </p>
      *
      * @param name The name of the service.
-     * @return The newly created channel for the given service.
+     * @return The newly created channel for the given service. Might return null if the channel was intentionally
+     *         skipped.
      */
     default Channel createChannel(final String name) {
         return createChannel(name, Collections.emptyList());
@@ -66,7 +67,8 @@ default Channel createChannel(final String name) {
      *
      * @param name The name of the service.
      * @param interceptors A list of additional client interceptors that should be added to the channel.
-     * @return The newly created channel for the given service.
+     * @return The newly created channel for the given service. Might return null if the channel was intentionally
+     *         skipped.
      */
     default Channel createChannel(final String name, final List<ClientInterceptor> interceptors) {
         return createChannel(name, interceptors, false);
@@ -88,7 +90,8 @@ default Channel createChannel(final String name, final List<ClientInterceptor> i
      * @param name The name of the service.
      * @param interceptors A list of additional client interceptors that should be added to the channel.
      * @param sortInterceptors Whether the interceptors (both global and custom) should be sorted before being applied.
-     * @return The newly created channel for the given service.
+     * @return The newly created channel for the given service. Might return null if the channel was intentionally
+     *         skipped.
      */
     Channel createChannel(String name, List<ClientInterceptor> interceptors, boolean sortInterceptors);
 

grpc-client-spring-boot-autoconfigure/src/main/java/net/devh/boot/grpc/client/channelfactory/InProcessChannelFactory.java

@@ -17,6 +17,7 @@
 
 package net.devh.boot.grpc.client.channelfactory;
 
+import java.net.URI;
 import java.util.Collections;
 import java.util.List;
 
@@ -37,14 +38,21 @@
 @Slf4j
 public class InProcessChannelFactory extends AbstractChannelFactory<InProcessChannelBuilder> {
 
+    /**
+     * The scheme of this factory: {@value #SCHEME}.
+     */
+    public static final String SCHEME = "in-process";
+
     /**
      * Creates a new InProcessChannelFactory with the given properties.
      *
      * @param properties The properties for the channels to create.
      * @param globalClientInterceptorRegistry The interceptor registry to use.
      */
-    public InProcessChannelFactory(final GrpcChannelsProperties properties,
+    public InProcessChannelFactory(
+            final GrpcChannelsProperties properties,
             final GlobalClientInterceptorRegistry globalClientInterceptorRegistry) {
+
         this(properties, globalClientInterceptorRegistry, Collections.emptyList());
     }
 
@@ -55,16 +63,20 @@ public InProcessChannelFactory(final GrpcChannelsProperties properties,
      * @param globalClientInterceptorRegistry The interceptor registry to use.
      * @param channelConfigurers The channel configurers to use. Can be empty.
      */
-    public InProcessChannelFactory(final GrpcChannelsProperties properties,
+    public InProcessChannelFactory(
+            final GrpcChannelsProperties properties,
             final GlobalClientInterceptorRegistry globalClientInterceptorRegistry,
             final List<GrpcChannelConfigurer> channelConfigurers) {
+
         super(properties, globalClientInterceptorRegistry, channelConfigurers);
     }
 
     @Override
     protected InProcessChannelBuilder newChannelBuilder(final String name) {
-        log.debug("Creating new channel: {}", name);
-        return InProcessChannelBuilder.forName(name);
+        final URI address = getPropertiesFor(name).getAddress();
+        final String target = address == null ? name : address.getSchemeSpecificPart();
+        log.debug("Creating new channel: {}", target);
+        return InProcessChannelBuilder.forName(target);
     }
 
     @Override

grpc-client-spring-boot-autoconfigure/src/main/java/net/devh/boot/grpc/client/channelfactory/InProcessOrAlternativeChannelFactory.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2016-2021 Michael Zhang <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
+ * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+ * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.devh.boot.grpc.client.channelfactory;
+
+import java.util.List;
+
+import io.grpc.Channel;
+import io.grpc.ClientInterceptor;
+
+/**
+ * An dummy channel factory that always returns null. Useful for skipping specific channels during tests/profiles.
+ *
+ * @author Daniel Theuke ([email protected])
+ */
+public final class NullChannelFactory implements GrpcChannelFactory {
+
+    /**
+     * The scheme of this factory: {@value #SCHEME}.
+     */
+    public static final String SCHEME = "null";
+
+    @Override
+    public Channel createChannel(
+            final String name,
+            final List<ClientInterceptor> interceptors,
+            final boolean sortInterceptors) {
+        return null;
+    }
+
+    @Override
+    public void close() {
+        // Nothing to do
+    }
+
+}