Added DataBuffer Encoder/Decoder

This commit adds a DataBuffer Encoder and Decoder, and uses it in
the annotation-based processing model.

Note that these codecs are not used in the functional processing model,
since the BodyInserter/BodyExtractor already have methods for
writing/reading DataBuffers.

Issue: SPR-15148

spring-core/src/test/java/org/springframework/core/codec/DataBufferDecoderTests.java

@@ -0,0 +1,63 @@
+/*
+ * 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.
+ * 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;
+
+import java.nio.ByteBuffer;
+import java.util.Collections;
+
+import org.junit.Test;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.AbstractDataBufferAllocatingTestCase;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.util.MimeTypeUtils;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Sebastien Deleuze
+ */
+public class DataBufferDecoderTests extends AbstractDataBufferAllocatingTestCase {
+
+	private final DataBufferDecoder decoder = new DataBufferDecoder();
+
+	@Test
+	public void canDecode() {
+		assertTrue(this.decoder.canDecode(ResolvableType.forClass(DataBuffer.class),
+				MimeTypeUtils.TEXT_PLAIN));
+		assertFalse(this.decoder.canDecode(ResolvableType.forClass(Integer.class),
+				MimeTypeUtils.TEXT_PLAIN));
+		assertTrue(this.decoder.canDecode(ResolvableType.forClass(DataBuffer.class),
+				MimeTypeUtils.APPLICATION_JSON));
+	}
+
+	@Test
+	public void decode() {
+		DataBuffer fooBuffer = stringBuffer("foo");
+		DataBuffer barBuffer = stringBuffer("bar");
+		Flux<DataBuffer> source = Flux.just(fooBuffer, barBuffer);
+		Flux<DataBuffer> output = this.decoder.decode(source,
+				ResolvableType.forClassWithGenerics(Publisher.class, ByteBuffer.class),
+				null, Collections.emptyMap());
+
+		assertSame(source, output);
+	}
+}

spring-core/src/test/java/org/springframework/core/codec/DataBufferEncoderTests.java

@@ -0,0 +1,65 @@
+/*
+ * 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.
+ * 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;
+
+import java.nio.ByteBuffer;
+import java.util.Collections;
+
+import org.junit.Test;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.AbstractDataBufferAllocatingTestCase;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.util.MimeTypeUtils;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author Sebastien Deleuze
+ */
+public class DataBufferEncoderTests extends AbstractDataBufferAllocatingTestCase {
+
+	private final DataBufferEncoder encoder = new DataBufferEncoder();
+
+	@Test
+	public void canEncode() {
+		assertTrue(this.encoder.canEncode(ResolvableType.forClass(DataBuffer.class),
+				MimeTypeUtils.TEXT_PLAIN));
+		assertFalse(this.encoder.canEncode(ResolvableType.forClass(Integer.class),
+				MimeTypeUtils.TEXT_PLAIN));
+		assertTrue(this.encoder.canEncode(ResolvableType.forClass(DataBuffer.class),
+				MimeTypeUtils.APPLICATION_JSON));
+	}
+
+	@Test
+	public void encode() {
+		DataBuffer fooBuffer = stringBuffer("foo");
+		DataBuffer barBuffer = stringBuffer("bar");
+		Flux<DataBuffer> source = Flux.just(fooBuffer, barBuffer);
+
+		Flux<DataBuffer> output = this.encoder.encode(source, this.bufferFactory,
+				ResolvableType.forClassWithGenerics(Publisher.class, ByteBuffer.class),
+				null, Collections.emptyMap());
+
+		assertSame(source, output);
+	}
+
+}