Add support for using WebFlux's WebTestClient to document an API

Closes gh-384

spring-restdocs-core/src/main/java/org/springframework/restdocs/RestDocumentationExtension.java

@@ -23,7 +23,6 @@ import org.junit.jupiter.api.extension.BeforeEachCallback;
 import org.junit.jupiter.api.extension.Extension;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
-import org.junit.jupiter.api.extension.ParameterResolutionException;
 import org.junit.jupiter.api.extension.ParameterResolver;
 import org.junit.jupiter.api.extension.TestExtensionContext;
 
@@ -59,14 +58,14 @@ public class RestDocumentationExtension implements Extension, BeforeEachCallback
 
 	@Override
 	public boolean supports(ParameterContext parameterContext,
-			ExtensionContext extensionContext) throws ParameterResolutionException {
+			ExtensionContext extensionContext) {
 		return RestDocumentationContextProvider.class
 				.isAssignableFrom(parameterContext.getParameter().getType());
 	}
 
 	@Override
 	public Object resolve(ParameterContext parameterContext,
-			ExtensionContext extensionContext) throws ParameterResolutionException {
+			ExtensionContext extensionContext) {
 		return this;
 	}
 

spring-restdocs-core/src/main/java/org/springframework/restdocs/generate/RestDocumentationGenerator.java

@@ -22,6 +22,7 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.BiFunction;
 
 import org.springframework.restdocs.operation.Operation;
 import org.springframework.restdocs.operation.OperationRequest;
@@ -242,12 +243,13 @@ public final class RestDocumentationGenerator<REQ, RESP> {
 
 	private OperationRequest preprocessRequest(OperationRequest request,
 			Map<String, Object> configuration) {
-		List<OperationRequestPreprocessor> requestPreprocessors = getRequestPreprocessors(
-				configuration);
-		for (OperationRequestPreprocessor preprocessor : requestPreprocessors) {
-			request = preprocessor.preprocess(request);
-		}
-		return request;
+		return preprocess(getRequestPreprocessors(configuration), request,
+				this::preprocess);
+	}
+
+	private OperationRequest preprocess(OperationRequestPreprocessor preprocessor,
+			OperationRequest request) {
+		return preprocessor.preprocess(request);
 	}
 
 	private List<OperationRequestPreprocessor> getRequestPreprocessors(
@@ -259,11 +261,13 @@ public final class RestDocumentationGenerator<REQ, RESP> {
 
 	private OperationResponse preprocessResponse(OperationResponse response,
 			Map<String, Object> configuration) {
-		for (OperationResponsePreprocessor preprocessor : getResponsePreprocessors(
-				configuration)) {
-			response = preprocessor.preprocess(response);
-		}
-		return response;
+		return preprocess(getResponsePreprocessors(configuration), response,
+				this::preprocess);
+	}
+
+	private OperationResponse preprocess(OperationResponsePreprocessor preprocessor,
+			OperationResponse response) {
+		return preprocessor.preprocess(response);
 	}
 
 	private List<OperationResponsePreprocessor> getResponsePreprocessors(
@@ -273,6 +277,15 @@ public final class RestDocumentationGenerator<REQ, RESP> {
 				configuration);
 	}
 
+	private <P, T> T preprocess(List<P> preprocessors, T target,
+			BiFunction<P, T, T> function) {
+		T processed = target;
+		for (P preprocessor : preprocessors) {
+			processed = function.apply(preprocessor, processed);
+		}
+		return processed;
+	}
+
 	@SuppressWarnings("unchecked")
 	private <T> List<T> getPreprocessors(T preprocessor, String preprocessorAttribute,
 			Map<String, Object> configuration) {

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/JsonFieldProcessor.java

@@ -49,11 +49,6 @@ final class JsonFieldProcessor {
 				matches.add(match.getValue());
 			}
 
-			@Override
-			public void absent() {
-
-			}
-
 		});
 		if (matches.isEmpty()) {
 			throw new FieldDoesNotExistException(path);
@@ -72,11 +67,6 @@ final class JsonFieldProcessor {
 						match.remove();
 					}
 
-					@Override
-					public void absent() {
-
-					}
-
 				});
 	}
 
@@ -89,11 +79,6 @@ final class JsonFieldProcessor {
 						match.removeSubsection();
 					}
 
-					@Override
-					public void absent() {
-
-					}
-
 				});
 	}
 
@@ -376,7 +361,8 @@ final class JsonFieldProcessor {
 
 		void foundMatch(Match match);
 
-		void absent();
+		default void absent() {
+		}
 
 	}