Fixes in response to code review by @ST-DDT

Author: liqweed

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

@@ -22,8 +22,11 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Member;
 import java.lang.reflect.Method;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
 
+import org.springframework.beans.BeanInstantiationException;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.InvalidPropertyException;
 import org.springframework.beans.factory.BeanCreationException;
@@ -57,7 +60,7 @@ public class GrpcClientBeanPostProcessor implements BeanPostProcessor {
     // which could lead to problems with the correct bean setup.
     private GrpcChannelFactory channelFactory = null;
     private List<StubTransformer> stubTransformers = null;
-    private final List<StubFactory> stubFactories;
+    private List<StubFactory> stubFactories = null;
 
     /**
      * Creates a new GrpcClientBeanPostProcessor with the given ApplicationContext.
@@ -67,7 +70,6 @@ public class GrpcClientBeanPostProcessor implements BeanPostProcessor {
      */
     public GrpcClientBeanPostProcessor(final ApplicationContext applicationContext) {
         this.applicationContext = requireNonNull(applicationContext, "applicationContext");
-        stubFactories = new ArrayList<>(applicationContext.getBeansOfType(StubFactory.class).values());
     }
 
     @Override
@@ -226,25 +228,36 @@ protected <T> T valueForMember(final String name, final Member injectionTarget,
     }
 
     /**
-     * Creates a stub instance for the specified stub type.
+     * Creates a stub instance for the specified stub type using the resolved {@link StubFactory}.
      * 
      * @param stubClass
      * @param channel
-     * @throws IllegalArgumentException If the method was called with an unsupported stub type.
-     * @throws IllegalStateException If failed creating the stub instance.
-     * @return
+     * @throws BeanInstantiationException If the stub couldn't be created, either because the type isn't supported or because of a failure in creation.
+     * @return A newly created gRPC stub.
      */
     private AbstractStub<?> createStub(Class<? extends AbstractStub<?>> stubClass, Channel channel) {
-        final StubFactory factory = this.stubFactories.stream()
+        final StubFactory factory = getStubFactories().stream()
                 .filter(stubFactory -> stubFactory.isApplicable(stubClass))
                 .findFirst()
-                .orElseThrow(() -> new IllegalArgumentException(
+                .orElseThrow(() -> new BeanInstantiationException(stubClass,
                         "Unsupported stub type: " + stubClass.getName() + " -> Please report this issue."));
 
         try {
             return factory.createStub(stubClass, channel);
         } catch (Exception exception) {
-            throw new IllegalStateException("Failed to create gRPC stub of type " + stubClass.getName(), exception);
+            throw new BeanInstantiationException(stubClass, "Failed to create gRPC stub of type " + stubClass.getName(), exception);
         }
     }
+
+    /**
+     * Lazy getter for the list of defined {@link StubFactory} beans.
+     *
+     * @return A list of all defined {@link StubFactory} beans.
+     */
+    private List<StubFactory> getStubFactories() {
+        if (this.stubFactories == null) {
+            stubFactories = new ArrayList<>(applicationContext.getBeansOfType(StubFactory.class).values());
+        }
+        return stubFactories;
+    }
 }

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

@@ -17,47 +17,27 @@
 
 package net.devh.boot.grpc.client.stubfactory;
 
-import java.lang.reflect.Constructor;
-import java.lang.reflect.Method;
-
-import org.springframework.beans.BeanInstantiationException;
-
 import io.grpc.Channel;
 import io.grpc.stub.AbstractStub;
+import org.springframework.beans.BeanInstantiationException;
+
+import java.lang.reflect.Method;
 
 /**
  * A factory for creating stubs provided by standard grpc Java library. This is an abstract super-type that can be
  * extended to support the different provided types.
  */
 public abstract class StandardJavaGrpcStubFactory implements StubFactory {
 
-    /**
-     * Creates a stub of the given type.
-     *
-     * @param stubType The type of the stub to create.
-     * @param channel The channel used to create the stub.
-     * @return The newly created stub.
-     *
-     * @throws BeanInstantiationException If the stub couldn't be created.
-     */
     @Override
     public AbstractStub<?> createStub(final Class<? extends AbstractStub<?>> stubType, final Channel channel) {
         try {
-            // First try the public static factory method
+            // Use the public static factory method
             final String methodName = getFactoryMethodName();
             final Class<?> enclosingClass = stubType.getEnclosingClass();
             final Method factoryMethod = enclosingClass.getMethod(methodName, Channel.class);
             return stubType.cast(factoryMethod.invoke(null, channel));
         } catch (final Exception e) {
-            try {
-                // Use the private constructor as backup
-                final Constructor<? extends AbstractStub<?>> constructor =
-                        stubType.getDeclaredConstructor(Channel.class);
-                constructor.setAccessible(true);
-                return constructor.newInstance(channel);
-            } catch (final Exception e1) {
-                e.addSuppressed(e1);
-            }
             throw new BeanInstantiationException(stubType, "Failed to create gRPC client", e);
         }
     }

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

@@ -19,10 +19,31 @@
 
 import io.grpc.Channel;
 import io.grpc.stub.AbstractStub;
+import org.springframework.beans.BeanInstantiationException;
 
+/**
+ * A factory for gRPC stubs. This is an extension mechanism for supporting different types of gRPC compiled stubs
+ * in addition to the standard Java compiled gRPC.
+ *
+ * Spring beans implementing this type will be picked up automatically and added to the list of supported types.
+ */
 public interface StubFactory {
 
+    /**
+     * Creates a stub of the given type.
+     *
+     * @param stubType The type of the stub to create.
+     * @param channel The channel used to create the stub.
+     * @return The newly created stub.
+     *
+     * @throws BeanInstantiationException If the stub couldn't be created.
+     */
     AbstractStub<?> createStub(final Class<? extends AbstractStub<?>> stubType, final Channel channel);
 
+    /**
+     * Used to resolve a factory that matches the particular stub type.
+     * @param stubType The type of the stub that needs to be created.
+     * @return True if this particular factory is capable of creating instances of this stub type. False otherwise.
+     */
     boolean isApplicable(Class<? extends AbstractStub<?>> stubType);
 }