Minor Jackson encoder/decoder refactoring

Consolidate JsonView hint extraction in shared base class.

Rename base class from AbstractJackson2Codec to Jackson2CodecSupport
since the class mainly provides support methods.

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Codec.java → spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,34 +16,46 @@
 
 package org.springframework.http.codec.json;
 
+import java.lang.annotation.Annotation;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.lang.reflect.TypeVariable;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
 
+import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.type.TypeFactory;
 
+import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
+import org.springframework.util.MimeTypeUtils;
 
 /**
- * Abstract base class for Jackson based decoder/encoder implementations.
+ * Base class providing support methods for Jackson 2 encoding and decoding.
  *
  * @author Sebastien Deleuze
+ * @author Rossen Stoyanchev
+ * @since 5.0
  */
-public class AbstractJackson2Codec {
+public abstract class Jackson2CodecSupport {
 
 	/**
-	 * Hint key to use with a {@link Class} value specifying the JSON View to use to serialize
-	 * or deserialize an object.
+	 * The key for the hint to specify a "JSON View" for encoding or decoding
+	 * with the value expected to be a {@link Class}.
 	 * @see <a href="http://wiki.fasterxml.com/JacksonJsonViews">Jackson JSON Views</a>
 	 */
-	public static final String JSON_VIEW_HINT = AbstractJackson2Codec.class.getName() + ".jsonView";
+	public static final String JSON_VIEW_HINT = Jackson2CodecSupport.class.getName() + ".jsonView";
+
+	private static final String JSON_VIEW_HINT_ERROR =
+			"@JsonView only supported for write hints with exactly 1 class argument: ";
 
 	protected static final List<MimeType> JSON_MIME_TYPES = Arrays.asList(
 				new MimeType("application", "json", StandardCharsets.UTF_8),
@@ -54,10 +66,9 @@ public class AbstractJackson2Codec {
 
 
 	/**
-	 * Create a new Jackson codec for the given mapper.
-	 * @param mapper the Jackson ObjectMapper to use
+	 * Constructor with a Jackson {@link ObjectMapper} to use.
 	 */
-	protected AbstractJackson2Codec(ObjectMapper mapper) {
+	protected Jackson2CodecSupport(ObjectMapper mapper) {
 		Assert.notNull(mapper, "ObjectMapper must not be null");
 		this.mapper = mapper;
 	}
@@ -141,4 +152,22 @@ public class AbstractJackson2Codec {
 		return ResolvableType.NONE;
 	}
 
+	protected Map<String, Object> getHints(ResolvableType actualType) {
+		return getParameter(actualType)
+				.flatMap(parameter -> Optional.ofNullable(getAnnotation(parameter, JsonView.class))
+						.map(annotation -> {
+							Class<?>[] classes = annotation.value();
+							Assert.isTrue(classes.length == 1, JSON_VIEW_HINT_ERROR + parameter);
+							return Collections.<String, Object>singletonMap(JSON_VIEW_HINT, classes[0]);
+						}))
+				.orElse(Collections.emptyMap());
+	}
+
+	protected Optional<MethodParameter> getParameter(ResolvableType type) {
+		return Optional.ofNullable (type.getSource() instanceof MethodParameter ?
+				(MethodParameter) type.getSource() : null);
+	}
+
+	protected abstract <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType);
+
 }

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2JsonDecoder.java

@@ -17,11 +17,10 @@
 package org.springframework.http.codec.json;
 
 import java.io.IOException;
-import java.util.Collections;
+import java.lang.annotation.Annotation;
 import java.util.List;
 import java.util.Map;
 
-import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectReader;
@@ -49,11 +48,11 @@ import org.springframework.util.MimeType;
  * @since 5.0
  * @see Jackson2JsonEncoder
  */
-public class Jackson2JsonDecoder extends AbstractJackson2Codec implements ServerHttpDecoder<Object> {
+public class Jackson2JsonDecoder extends Jackson2CodecSupport implements ServerHttpDecoder<Object> {
 
-	private final JsonObjectDecoder fluxObjectDecoder = new JsonObjectDecoder(true);
+	private final JsonObjectDecoder fluxDecoder = new JsonObjectDecoder(true);
 
-	private final JsonObjectDecoder monoObjectDecoder = new JsonObjectDecoder(false);
+	private final JsonObjectDecoder monoDecoder = new JsonObjectDecoder(false);
 
 
 	public Jackson2JsonDecoder() {
@@ -78,19 +77,17 @@ public class Jackson2JsonDecoder extends AbstractJackson2Codec implements Server
 	}
 
 	@Override
-	public Flux<Object> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
+	public Flux<Object> decode(Publisher<DataBuffer> input, ResolvableType elementType,
 			MimeType mimeType, Map<String, Object> hints) {
 
-		JsonObjectDecoder objectDecoder = this.fluxObjectDecoder;
-		return decodeInternal(objectDecoder, inputStream, elementType, mimeType, hints);
+		return decodeInternal(this.fluxDecoder, input, elementType, mimeType, hints);
 	}
 
 	@Override
-	public Mono<Object> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementType,
+	public Mono<Object> decodeToMono(Publisher<DataBuffer> input, ResolvableType elementType,
 			MimeType mimeType, Map<String, Object> hints) {
 
-		JsonObjectDecoder objectDecoder = this.monoObjectDecoder;
-		return decodeInternal(objectDecoder, inputStream, elementType, mimeType, hints).singleOrEmpty();
+		return decodeInternal(this.monoDecoder, input, elementType, mimeType, hints).singleOrEmpty();
 	}
 
 	private Flux<Object> decodeInternal(JsonObjectDecoder objectDecoder, Publisher<DataBuffer> inputStream,
@@ -99,20 +96,13 @@ public class Jackson2JsonDecoder extends AbstractJackson2Codec implements Server
 		Assert.notNull(inputStream, "'inputStream' must not be null");
 		Assert.notNull(elementType, "'elementType' must not be null");
 
-		MethodParameter methodParam = (elementType.getSource() instanceof MethodParameter ?
-				(MethodParameter) elementType.getSource() : null);
-		Class<?> contextClass = (methodParam != null ? methodParam.getContainingClass() : null);
+		Class<?> contextClass = getParameter(elementType).map(MethodParameter::getContainingClass).orElse(null);
 		JavaType javaType = getJavaType(elementType.getType(), contextClass);
+		Class<?> jsonView = (Class<?>) hints.get(Jackson2CodecSupport.JSON_VIEW_HINT);
 
-		ObjectReader reader;
-		Class<?> jsonView = (Class<?>)hints.get(AbstractJackson2Codec.JSON_VIEW_HINT);
-
-		if (jsonView != null) {
-			reader = this.mapper.readerWithView(jsonView).forType(javaType);
-		}
-		else {
-			reader = this.mapper.readerFor(javaType);
-		}
+		ObjectReader reader = jsonView != null ?
+				this.mapper.readerWithView(jsonView).forType(javaType) :
+				this.mapper.readerFor(javaType);
 
 		return objectDecoder.decode(inputStream, elementType, mimeType, hints)
 				.map(dataBuffer -> {
@@ -134,20 +124,12 @@ public class Jackson2JsonDecoder extends AbstractJackson2Codec implements Server
 	public Map<String, Object> getDecodeHints(ResolvableType actualType, ResolvableType elementType,
 			ServerHttpRequest request, ServerHttpResponse response) {
 
-		Object source = actualType.getSource();
-		MethodParameter parameter = (source instanceof MethodParameter ? (MethodParameter)source : null);
-		if (parameter != null) {
-			JsonView annotation = parameter.getParameterAnnotation(JsonView.class);
-			if (annotation != null) {
-				Class<?>[] classes = annotation.value();
-				if (classes.length != 1) {
-					throw new IllegalArgumentException(
-							"@JsonView only supported for read hints with exactly 1 class argument: " + parameter);
-				}
-				return Collections.singletonMap(AbstractJackson2Codec.JSON_VIEW_HINT, classes[0]);
-			}
-		}
-		return Collections.emptyMap();
+		return getHints(actualType);
+	}
+
+	@Override
+	protected <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType) {
+		return parameter.getParameterAnnotation(annotType);
 	}
 
 }

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2JsonEncoder.java

@@ -18,11 +18,10 @@ package org.springframework.http.codec.json;
 
 import java.io.IOException;
 import java.io.OutputStream;
-import java.util.HashMap;
+import java.lang.annotation.Annotation;
 import java.util.List;
 import java.util.Map;
 
-import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.core.PrettyPrinter;
 import com.fasterxml.jackson.core.util.DefaultIndenter;
 import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
@@ -61,7 +60,7 @@ import static org.springframework.http.MediaType.APPLICATION_STREAM_JSON;
  * @since 5.0
  * @see Jackson2JsonDecoder
  */
-public class Jackson2JsonEncoder extends AbstractJackson2Codec implements ServerHttpEncoder<Object> {
+public class Jackson2JsonEncoder extends Jackson2CodecSupport implements ServerHttpEncoder<Object> {
 
 	private final PrettyPrinter ssePrettyPrinter;
 
@@ -112,30 +111,24 @@ public class Jackson2JsonEncoder extends AbstractJackson2Codec implements Server
 	}
 
 	private DataBuffer encodeValue(Object value, DataBufferFactory bufferFactory,
-			ResolvableType type, Map<String, Object> hints) {
+			ResolvableType elementType, Map<String, Object> hints) {
 
 		TypeFactory typeFactory = this.mapper.getTypeFactory();
-		JavaType javaType = typeFactory.constructType(type.getType());
-		if (type.isInstance(value)) {
-			javaType = getJavaType(type.getType(), null);
+		JavaType javaType = typeFactory.constructType(elementType.getType());
+		if (elementType.isInstance(value)) {
+			javaType = getJavaType(elementType.getType(), null);
 		}
 
-		ObjectWriter writer;
-		Class<?> jsonView = (Class<?>)hints.get(AbstractJackson2Codec.JSON_VIEW_HINT);
-		if (jsonView != null) {
-			writer = this.mapper.writerWithView(jsonView);
-		}
-		else {
-			writer = this.mapper.writer();
-		}
+		Class<?> jsonView = (Class<?>) hints.get(Jackson2CodecSupport.JSON_VIEW_HINT);
+		ObjectWriter writer = jsonView != null ? this.mapper.writerWithView(jsonView): this.mapper.writer();
 
 		if (javaType != null && javaType.isContainerType()) {
 			writer = writer.forType(javaType);
 		}
 
-		Boolean sse = (Boolean)hints.get(ServerSentEventHttpMessageWriter.SSE_CONTENT_HINT);
 		SerializationConfig config = writer.getConfig();
-		if (Boolean.TRUE.equals(sse) && config.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
+		Boolean sseHint = (Boolean) hints.get(ServerSentEventHttpMessageWriter.SSE_CONTENT_HINT);
+		if (Boolean.TRUE.equals(sseHint) && config.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
 			writer = writer.with(this.ssePrettyPrinter);
 		}
 
@@ -158,21 +151,12 @@ public class Jackson2JsonEncoder extends AbstractJackson2Codec implements Server
 	public Map<String, Object> getEncodeHints(ResolvableType actualType, ResolvableType elementType,
 			MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
 
-		Map<String, Object> hints = new HashMap<>();
-		Object source = actualType.getSource();
-		MethodParameter returnValue = (source instanceof MethodParameter ? (MethodParameter)source : null);
-		if (returnValue != null) {
-			JsonView annotation = returnValue.getMethodAnnotation(JsonView.class);
-			if (annotation != null) {
-				Class<?>[] classes = annotation.value();
-				if (classes.length != 1) {
-					throw new IllegalArgumentException(
-							"@JsonView only supported for write hints with exactly 1 class argument: " + returnValue);
-				}
-				hints.put(AbstractJackson2Codec.JSON_VIEW_HINT, classes[0]);
-			}
-		}
-		return hints;
+		return getHints(actualType);
+	}
+
+	@Override
+	protected <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType) {
+		return parameter.getMethodAnnotation(annotType);
 	}
 
 }

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/EntityResponse.java

@@ -29,7 +29,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
-import org.springframework.http.codec.json.AbstractJackson2Codec;
+import org.springframework.http.codec.json.Jackson2CodecSupport;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.web.reactive.function.BodyInserter;
 import org.springframework.web.reactive.function.BodyInserters;
@@ -207,7 +207,7 @@ public interface EntityResponse<T> extends ServerResponse {
 		Builder<T> contentType(MediaType contentType);
 
 		/**
-		 * Add a serialization hint like {@link AbstractJackson2Codec#JSON_VIEW_HINT} to
+		 * Add a serialization hint like {@link Jackson2CodecSupport#JSON_VIEW_HINT} to
 		 * customize how the body will be serialized.
 		 * @param key the hint key
 		 * @param value the hint value

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerRequest.java

@@ -32,7 +32,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.MediaType;
-import org.springframework.http.codec.json.AbstractJackson2Codec;
+import org.springframework.http.codec.json.Jackson2CodecSupport;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.web.reactive.function.BodyExtractor;
 import org.springframework.web.server.WebSession;
@@ -82,7 +82,7 @@ public interface ServerRequest {
 	/**
 	 * Extract the body with the given {@code BodyExtractor} and hints.
 	 * @param extractor the {@code BodyExtractor} that reads from the request
-	 * @param hints the map of hints like {@link AbstractJackson2Codec#JSON_VIEW_HINT}
+	 * @param hints the map of hints like {@link Jackson2CodecSupport#JSON_VIEW_HINT}
 	 * to use to customize body extraction
 	 * @param <T> the type of the body returned
 	 * @return the extracted body

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerResponse.java

@@ -31,7 +31,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
-import org.springframework.http.codec.json.AbstractJackson2Codec;
+import org.springframework.http.codec.json.Jackson2CodecSupport;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.function.BodyInserter;
@@ -326,7 +326,7 @@ public interface ServerResponse {
 		BodyBuilder contentType(MediaType contentType);
 
 		/**
-		 * Add a serialization hint like {@link AbstractJackson2Codec#JSON_VIEW_HINT}
+		 * Add a serialization hint like {@link Jackson2CodecSupport#JSON_VIEW_HINT}
 		 * to customize how the body will be serialized.
 		 * @param key the hint key
 		 * @param value the hint value

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyExtractorsTests.java

@@ -50,7 +50,7 @@ import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
 import org.springframework.util.MultiValueMap;
 
 import static org.junit.Assert.*;
-import static org.springframework.http.codec.json.AbstractJackson2Codec.*;
+import static org.springframework.http.codec.json.Jackson2CodecSupport.*;
 
 /**
  * @author Arjen Poutsma

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyInsertersTests.java

@@ -61,7 +61,7 @@ import org.springframework.util.MultiValueMap;
 
 import static java.nio.charset.StandardCharsets.*;
 import static org.junit.Assert.*;
-import static org.springframework.http.codec.json.AbstractJackson2Codec.*;
+import static org.springframework.http.codec.json.Jackson2CodecSupport.*;
 
 /**
  * @author Arjen Poutsma