Introduce ResourceEncoder and ResourceDecoder

This commit introduces the ResourceEncoder and ResourceDecoder, and uses
these in ResourceHttpMessageConverter as a non-zero-copy fallback
method.

spring-web-reactive/src/main/java/org/springframework/core/codec/support/ResourceDecoder.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.codec.support;
+
+import java.io.InputStream;
+
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.InputStreamResource;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.support.DataBufferUtils;
+import org.springframework.util.MimeType;
+import org.springframework.util.MimeTypeUtils;
+
+/**
+ * A decoder for {@link Resource}s.
+ *
+ * @author Arjen Poutsma
+ */
+public class ResourceDecoder extends AbstractDecoder<Resource> {
+
+	public ResourceDecoder() {
+		super(MimeTypeUtils.ALL);
+	}
+
+	@Override
+	public boolean canDecode(ResolvableType type, MimeType mimeType, Object... hints) {
+		Class<?> clazz = type.getRawClass();
+		return (InputStreamResource.class.equals(clazz) ||
+				clazz.isAssignableFrom(ByteArrayResource.class)) &&
+				super.canDecode(type, mimeType, hints);
+	}
+
+	@Override
+	public Flux<Resource> decode(Publisher<DataBuffer> inputStream, ResolvableType type,
+			MimeType mimeType, Object... hints) {
+		Class<?> clazz = type.getRawClass();
+
+		Flux<DataBuffer> body = Flux.from(inputStream);
+
+		if (InputStreamResource.class.equals(clazz)) {
+			InputStream is = DataBufferUtils.toInputStream(body);
+			return Flux.just(new InputStreamResource(is));
+		}
+		else if (clazz.isAssignableFrom(ByteArrayResource.class)) {
+			Mono<DataBuffer> singleBuffer = body.reduce(DataBuffer::write);
+			return Flux.from(singleBuffer.map(buffer -> {
+				byte[] bytes = new byte[buffer.readableByteCount()];
+				buffer.read(bytes);
+				return new ByteArrayResource(bytes);
+			}));
+		}
+		else {
+			return Flux.error(new IllegalStateException(
+					"Unsupported resource class: " + clazz));
+		}
+	}
+}

spring-web-reactive/src/main/java/org/springframework/core/codec/support/ResourceEncoder.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.codec.support;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferAllocator;
+import org.springframework.core.io.buffer.support.DataBufferUtils;
+import org.springframework.util.Assert;
+import org.springframework.util.MimeType;
+import org.springframework.util.MimeTypeUtils;
+import org.springframework.util.StreamUtils;
+
+/**
+ * An encoder for {@link Resource}s.
+ * @author Arjen Poutsma
+ */
+public class ResourceEncoder extends AbstractEncoder<Resource> {
+
+	public static final int DEFAULT_BUFFER_SIZE = StreamUtils.BUFFER_SIZE;
+
+	private final int bufferSize;
+
+	public ResourceEncoder() {
+		this(DEFAULT_BUFFER_SIZE);
+	}
+
+	public ResourceEncoder(int bufferSize) {
+		super(MimeTypeUtils.ALL);
+		Assert.isTrue(bufferSize > 0, "'bufferSize' must be larger than 0");
+		this.bufferSize = bufferSize;
+	}
+
+	@Override
+	public boolean canEncode(ResolvableType type, MimeType mimeType, Object... hints) {
+		Class<?> clazz = type.getRawClass();
+		return (super.canEncode(type, mimeType, hints) &&
+				Resource.class.isAssignableFrom(clazz));
+	}
+
+	@Override
+	public Flux<DataBuffer> encode(Publisher<? extends Resource> inputStream,
+			DataBufferAllocator allocator, ResolvableType type, MimeType mimeType,
+			Object... hints) {
+		return Flux.from(inputStream).
+				concatMap(resource -> {
+					try {
+						InputStream is = resource.getInputStream();
+						return DataBufferUtils.read(is, allocator, this.bufferSize);
+					}
+					catch (IOException ex) {
+						return Mono.error(ex);
+					}
+				});
+	}
+}

spring-web-reactive/src/main/java/org/springframework/core/codec/support/StringEncoder.java

@@ -45,7 +45,7 @@ public class StringEncoder extends AbstractEncoder<String> {
 	@Override
 	public boolean canEncode(ResolvableType type, MimeType mimeType, Object... hints) {
 		Class<?> clazz = type.getRawClass();
-		return (super.canEncode(type, mimeType, hints) && String.class.isAssignableFrom(clazz));
+		return (super.canEncode(type, mimeType, hints) && String.class.equals(clazz));
 	}
 
 	@Override

spring-web-reactive/src/main/java/org/springframework/core/io/support/ResourceUtils2.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.io.support;
+
+import java.io.IOException;
+import java.net.URI;
+
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.DescriptiveResource;
+import org.springframework.core.io.InputStreamResource;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+import org.springframework.util.ResourceUtils;
+
+/**
+ * @author Arjen Poutsma
+ */
+public abstract class ResourceUtils2 {
+
+	/**
+	 * Indicates whether the given resource has a file, so that {@link
+	 * Resource#getFile()}
+	 * can be called without an {@link java.io.IOException}.
+	 * @param resource the resource to check
+	 * @return {@code true} if the given resource has a file; {@code false} otherwise
+	 */
+	// TODO: refactor into Resource.hasFile() method
+	public static boolean hasFile(Resource resource) {
+		Assert.notNull(resource, "'resource' must not be null");
+
+		// the following Resource implementations do not support getURI/getFile
+		if (resource instanceof ByteArrayResource ||
+				resource instanceof DescriptiveResource ||
+				resource instanceof InputStreamResource) {
+			return false;
+		}
+		try {
+			URI resourceUri = resource.getURI();
+			return ResourceUtils.URL_PROTOCOL_FILE.equals(resourceUri.getScheme());
+		}
+		catch (IOException ignored) {
+		}
+		return false;
+	}
+}

spring-web-reactive/src/main/java/org/springframework/http/converter/reactive/CodecHttpMessageConverter.java

@@ -29,12 +29,16 @@ import org.springframework.core.codec.Decoder;
 import org.springframework.core.codec.Encoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferAllocator;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpInputMessage;
 import org.springframework.http.ReactiveHttpOutputMessage;
 import org.springframework.http.support.MediaTypeUtils;
 
 /**
+ * Implementation of the {@link HttpMessageConverter} interface that delegates to
+ * {@link Encoder} and {@link Decoder}.
+ *
  * @author Arjen Poutsma
  */
 public class CodecHttpMessageConverter<T> implements HttpMessageConverter<T> {
@@ -43,6 +47,32 @@ public class CodecHttpMessageConverter<T> implements HttpMessageConverter<T> {
 
 	private final Decoder<T> decoder;
 
+	/**
+	 * Create a {@code CodecHttpMessageConverter} with the given {@link Encoder}. When
+	 * using this constructor, all read-related methods will in {@code false} or an
+	 * {@link IllegalStateException}.
+	 * @param encoder the encoder to use
+	 */
+	public CodecHttpMessageConverter(Encoder<T> encoder) {
+		this(encoder, null);
+	}
+
+	/**
+	 * Create a {@code CodecHttpMessageConverter} with the given {@link Decoder}. When
+	 * using this constructor, all write-related methods will in {@code false} or an
+	 * {@link IllegalStateException}.
+	 * @param decoder the decoder to use
+	 */
+	public CodecHttpMessageConverter(Decoder<T> decoder) {
+		this(null, decoder);
+	}
+
+	/**
+	 * Create a {@code CodecHttpMessageConverter} with the given {@link Encoder} and
+	 * {@link Decoder}.
+	 * @param encoder the encoder to use, can be {@code null}
+	 * @param decoder the decoder to use, can be {@code null}
+	 */
 	public CodecHttpMessageConverter(Encoder<T> encoder, Decoder<T> decoder) {
 		this.encoder = encoder;
 		this.decoder = decoder;
@@ -94,9 +124,13 @@ public class CodecHttpMessageConverter<T> implements HttpMessageConverter<T> {
 		if (this.encoder == null) {
 			return Mono.error(new IllegalStateException("No decoder set"));
 		}
-		outputMessage.getHeaders().setContentType(contentType);
+		HttpHeaders headers = outputMessage.getHeaders();
+		if (headers.getContentType() == null) {
+			headers.setContentType(contentType);
+		}
 		DataBufferAllocator allocator = outputMessage.allocator();
-		Flux<DataBuffer> body = encoder.encode(inputStream, allocator, type, contentType);
+		Flux<DataBuffer> body =
+				this.encoder.encode(inputStream, allocator, type, contentType);
 		return outputMessage.setBody(body);
 	}
 }

spring-web-reactive/src/main/java/org/springframework/http/converter/reactive/ResourceHttpMessageConverter.java

@@ -18,10 +18,6 @@ package org.springframework.http.converter.reactive;
 
 import java.io.File;
 import java.io.IOException;
-import java.io.InputStream;
-import java.net.URI;
-import java.util.Collections;
-import java.util.List;
 import java.util.Optional;
 
 import org.reactivestreams.Publisher;
@@ -29,106 +25,46 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
-import org.springframework.core.io.ByteArrayResource;
-import org.springframework.core.io.DescriptiveResource;
+import org.springframework.core.codec.support.ResourceDecoder;
+import org.springframework.core.codec.support.ResourceEncoder;
 import org.springframework.core.io.InputStreamResource;
 import org.springframework.core.io.Resource;
-import org.springframework.core.io.buffer.DataBuffer;
-import org.springframework.core.io.buffer.support.DataBufferUtils;
+import org.springframework.core.io.support.ResourceUtils2;
 import org.springframework.http.HttpHeaders;
-import org.springframework.http.HttpRangeResource;
 import org.springframework.http.MediaType;
-import org.springframework.http.ReactiveHttpInputMessage;
 import org.springframework.http.ReactiveHttpOutputMessage;
 import org.springframework.http.ZeroCopyHttpOutputMessage;
 import org.springframework.http.support.MediaTypeUtils;
 import org.springframework.util.MimeTypeUtils2;
-import org.springframework.util.ResourceUtils;
-import org.springframework.util.StreamUtils;
 
 /**
+ * Implementation of {@link HttpMessageConverter} that can read and write
+ * {@link Resource Resources} and supports byte range requests.
+ **
  * @author Arjen Poutsma
  */
-public class ResourceHttpMessageConverter implements HttpMessageConverter<Resource> {
+public class ResourceHttpMessageConverter extends CodecHttpMessageConverter<Resource> {
 
-	private static final int BUFFER_SIZE = StreamUtils.BUFFER_SIZE;
-
-	private static final List<MediaType> SUPPORTED_MEDIA_TYPES =
-			Collections.singletonList(MediaType.ALL);
-
-	@Override
-	public boolean canRead(ResolvableType type, MediaType mediaType) {
-		return Resource.class.isAssignableFrom(type.getRawClass());
-	}
-
-	@Override
-	public boolean canWrite(ResolvableType type, MediaType mediaType) {
-		return Resource.class.isAssignableFrom(type.getRawClass());
-	}
-
-	@Override
-	public List<MediaType> getReadableMediaTypes() {
-		return SUPPORTED_MEDIA_TYPES;
+	public ResourceHttpMessageConverter() {
+		super(new ResourceEncoder(), new ResourceDecoder());
 	}
 
-	@Override
-	public List<MediaType> getWritableMediaTypes() {
-		return SUPPORTED_MEDIA_TYPES;
-	}
-
-	@Override
-	public Flux<Resource> read(ResolvableType type,
-			ReactiveHttpInputMessage inputMessage) {
-		Class<?> clazz = type.getRawClass();
-
-		Flux<DataBuffer> body = inputMessage.getBody();
-
-		if (InputStreamResource.class.equals(clazz)) {
-			InputStream is = DataBufferUtils.toInputStream(body);
-			return Flux.just(new InputStreamResource(is));
-		}
-		else if (clazz.isAssignableFrom(ByteArrayResource.class)) {
-			Mono<DataBuffer> singleBuffer = body.reduce(DataBuffer::write);
-			return Flux.from(singleBuffer.map(buffer -> {
-				byte[] bytes = new byte[buffer.readableByteCount()];
-				buffer.read(bytes);
-				return new ByteArrayResource(bytes);
-			}));
-		}
-		else {
-			return Flux.error(new IllegalStateException(
-					"Unsupported resource class: " + clazz));
-		}
+	public ResourceHttpMessageConverter(int bufferSize) {
+		super(new ResourceEncoder(bufferSize), new ResourceDecoder());
 	}
 
 	@Override
 	public Mono<Void> write(Publisher<? extends Resource> inputStream,
 			ResolvableType type, MediaType contentType,
 			ReactiveHttpOutputMessage outputMessage) {
-
-		if (inputStream instanceof Mono) {
-			// single resource
-			return Mono.from(Flux.from(inputStream).
-					flatMap(resource -> {
-						HttpHeaders headers = outputMessage.getHeaders();
-						addHeaders(headers, resource, contentType);
-
-						if (resource instanceof HttpRangeResource) {
-							return writePartialContent((HttpRangeResource) resource,
-									outputMessage);
-						}
-						else {
-							return writeContent(resource, outputMessage, 0, -1);
-						}
-
-
-					}));
-		}
-		else {
-			// multiple resources, not supported!
-			return Mono.error(new IllegalArgumentException(
-					"Multiple resources not yet supported"));
-		}
+		return Mono.from(Flux.from(inputStream).
+				take(1).
+				concatMap(resource -> {
+					HttpHeaders headers = outputMessage.getHeaders();
+					addHeaders(headers, resource, contentType);
+
+					return writeContent(resource, type, contentType, outputMessage);
+				}));
 	}
 
 	protected void addHeaders(HttpHeaders headers, Resource resource,
@@ -146,54 +82,24 @@ public class ResourceHttpMessageConverter implements HttpMessageConverter<Resour
 		if (headers.getContentLength() < 0) {
 			contentLength(resource).ifPresent(headers::setContentLength);
 		}
-		headers.add(HttpHeaders.ACCEPT_RANGES, "bytes");
 	}
 
-	private Mono<Void> writeContent(Resource resource,
-			ReactiveHttpOutputMessage outputMessage, long position, long count) {
+	private Mono<Void> writeContent(Resource resource, ResolvableType type,
+			MediaType contentType, ReactiveHttpOutputMessage outputMessage) {
 		if (outputMessage instanceof ZeroCopyHttpOutputMessage) {
 			Optional<File> file = getFile(resource);
 			if (file.isPresent()) {
 				ZeroCopyHttpOutputMessage zeroCopyResponse =
 						(ZeroCopyHttpOutputMessage) outputMessage;
 
-				if (count < 0) {
-					count = file.get().length();
-				}
-
-				return zeroCopyResponse.setBody(file.get(), position, count);
-			}
-		}
-
-		// non-zero copy fallback
-		try {
-			InputStream is = resource.getInputStream();
-			long skipped = is.skip(position);
-			if (skipped < position) {
-				return Mono.error(new IOException(
-						"Skipped only " + skipped + " bytes out of " + count +
-								" required."));
-			}
-
-			Flux<DataBuffer> responseBody =
-					DataBufferUtils.read(is, outputMessage.allocator(), BUFFER_SIZE);
-			if (count > 0) {
-				responseBody = DataBufferUtils.takeUntilByteCount(responseBody, count);
+				return zeroCopyResponse
+						.setBody(file.get(), (long) 0, file.get().length());
 			}
-
-			return outputMessage.setBody(responseBody);
-		}
-		catch (IOException ex) {
-			return Mono.error(ex);
 		}
-	}
-
-	protected Mono<Void> writePartialContent(HttpRangeResource resource,
-			ReactiveHttpOutputMessage outputMessage) {
-
-		// TODO: implement
 
-		return Mono.empty();
+		// non-zero copy fallback, using ResourceEncoder
+		return super.write(Mono.just(resource), type,
+				outputMessage.getHeaders().getContentType(), outputMessage);
 	}
 
 	private static Optional<Long> contentLength(Resource resource) {
@@ -210,18 +116,12 @@ public class ResourceHttpMessageConverter implements HttpMessageConverter<Resour
 	}
 
 	private static Optional<File> getFile(Resource resource) {
-		// TODO: introduce Resource.hasFile() property to bypass the potential IOException thrown in Resource.getFile()
-		// the following Resource implementations do not support getURI/getFile
-		if (!(resource instanceof ByteArrayResource ||
-				resource instanceof DescriptiveResource ||
-				resource instanceof InputStreamResource)) {
+		if (ResourceUtils2.hasFile(resource)) {
 			try {
-				URI resourceUri = resource.getURI();
-				if (ResourceUtils.URL_PROTOCOL_FILE.equals(resourceUri.getScheme())) {
-					return Optional.of(ResourceUtils.getFile(resourceUri));
-				}
+				return Optional.of(resource.getFile());
 			}
 			catch (IOException ignored) {
+				// should not happen
 			}
 		}
 		return Optional.empty();

spring-web-reactive/src/test/java/org/springframework/core/codec/support/ResourceDecoderTests.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.codec.support;
+
+import java.io.IOException;
+
+import org.junit.Test;
+import reactor.core.publisher.Flux;
+import reactor.core.test.TestSubscriber;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.InputStreamResource;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.http.MediaType;
+import org.springframework.util.StreamUtils;
+
+import static org.junit.Assert.*;
+
+/**
+ * @author Arjen Poutsma
+ */
+public class ResourceDecoderTests extends AbstractAllocatingTestCase {
+
+	private final ResourceDecoder decoder = new ResourceDecoder();
+
+	@Test
+	public void canDecode() throws Exception {
+		assertTrue(decoder.canDecode(ResolvableType.forClass(InputStreamResource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(decoder.canDecode(ResolvableType.forClass(ByteArrayResource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(decoder.canDecode(ResolvableType.forClass(Resource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(decoder.canDecode(ResolvableType.forClass(InputStreamResource.class),
+				MediaType.APPLICATION_JSON));
+	}
+
+	@Test
+	public void decode() throws Exception {
+		DataBuffer fooBuffer = stringBuffer("foo");
+		DataBuffer barBuffer = stringBuffer("bar");
+		Flux<DataBuffer> source = Flux.just(fooBuffer, barBuffer);
+
+		Flux<Resource> result =
+				decoder.decode(source, ResolvableType.forClass(Resource.class), null);
+
+		TestSubscriber<Resource> testSubscriber = new TestSubscriber<>();
+		testSubscriber.bindTo(result).
+				assertNoError().
+				assertComplete().
+				assertValuesWith(resource -> {
+					try {
+						byte[] bytes =
+								StreamUtils.copyToByteArray(resource.getInputStream());
+						assertEquals("foobar", new String(bytes));
+					}
+					catch (IOException e) {
+						fail(e.getMessage());
+					}
+				});
+
+	}
+
+}

spring-web-reactive/src/test/java/org/springframework/core/codec/support/ResourceEncoderTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.codec.support;
+
+import java.nio.charset.StandardCharsets;
+
+import org.junit.Test;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.core.test.TestSubscriber;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.InputStreamResource;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.http.MediaType;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Arjen Poutsma
+ */
+public class ResourceEncoderTests extends AbstractAllocatingTestCase {
+
+	private final ResourceEncoder encoder = new ResourceEncoder();
+
+	@Test
+	public void canEncode() throws Exception {
+		assertTrue(encoder.canEncode(ResolvableType.forClass(InputStreamResource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(encoder.canEncode(ResolvableType.forClass(ByteArrayResource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(encoder.canEncode(ResolvableType.forClass(Resource.class),
+				MediaType.TEXT_PLAIN));
+		assertTrue(encoder.canEncode(ResolvableType.forClass(InputStreamResource.class),
+				MediaType.APPLICATION_JSON));
+	}
+
+	@Test
+	public void encode() throws Exception {
+		String s = "foo";
+		Resource resource = new ByteArrayResource(s.getBytes(StandardCharsets.UTF_8));
+
+		Mono<Resource> source = Mono.just(resource);
+
+		Flux<DataBuffer> output =
+				encoder.encode(source, allocator, ResolvableType.forClass(Resource.class),
+						null);
+
+		TestSubscriber<DataBuffer> testSubscriber = new TestSubscriber<>();
+		testSubscriber.bindTo(output).assertNoError().assertComplete()
+				.assertValues(stringBuffer(s));
+
+	}
+
+}