INT-3779: Codec Support Part I - Transformers

JIRA: https://jira.spring.io/browse/INT-3779

MessageConverters and Docs to follow.

Author: garyrussell

spring-integration-core/src/main/java/org/springframework/integration/transformer/DecodingTransformer.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2015 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.integration.transformer;
+
+import org.springframework.expression.Expression;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.springframework.integration.codec.Codec;
+import org.springframework.integration.context.IntegrationContextUtils;
+import org.springframework.messaging.Message;
+import org.springframework.util.Assert;
+
+/**
+ * {@link AbstractPayloadTransformer} that delegates to a codec to decode the
+ * payload from a byte[].
+ *
+ * @author Gary Russell
+ * @since 4.2
+ *
+ */
+public class DecodingTransformer<T> extends AbstractTransformer {
+
+	private final Codec codec;
+
+	private final Class<T> type;
+
+	private final Expression typeExpression;
+
+	private volatile StandardEvaluationContext evaluationContext;
+
+	/**
+	 * Construct an instance to use the supplied codec to decode to the supplied type.
+	 * @param codec the codec.
+	 * @param type the type.
+	 */
+	public DecodingTransformer(Codec codec, Class<T> type) {
+		Assert.notNull(codec, "'codec' cannot be null");
+		Assert.notNull(type, "'type' cannot be null");
+		this.codec = codec;
+		this.type = type;
+		this.typeExpression = null;
+	}
+
+	/**
+	 * Construct an instance to use the supplied codec to decode to the supplied type.
+	 * @param codec the codec.
+	 * @param typeExpression an expression that evaluates to a {@link Class}.
+	 */
+	public DecodingTransformer(Codec codec, Expression typeExpression) {
+		Assert.notNull(codec, "'codec' cannot be null");
+		Assert.notNull(typeExpression, "'typeExpression' cannot be null");
+		this.codec = codec;
+		this.type = null;
+		this.typeExpression = typeExpression;
+	}
+
+	public void setEvaluationContext(StandardEvaluationContext evaluationContext) {
+		this.evaluationContext = evaluationContext;
+	}
+
+	@Override
+	protected void onInit() throws Exception {
+		if (this.evaluationContext == null) {
+			this.evaluationContext = IntegrationContextUtils.getEvaluationContext(getBeanFactory());
+		}
+	}
+
+	@Override
+	protected T doTransform(Message<?> message) throws Exception {
+		Assert.isTrue(message.getPayload() instanceof byte[], "Message payload must be byte[]");
+		byte[] bytes = (byte[]) message.getPayload();
+		return codec.decode(bytes, this.type != null ? this.type : type(message));
+	}
+
+	@SuppressWarnings("unchecked")
+	private Class<T> type(Message<?> message) {
+		Assert.state(this.evaluationContext != null, "EvaluationContext required");
+		return this.typeExpression.getValue(this.evaluationContext, message, Class.class);
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/transformer/EncodingPayloadTransformer.java

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+/*
+ * Copyright 2015 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.integration.transformer;
+
+import org.springframework.integration.codec.Codec;
+import org.springframework.util.Assert;
+
+/**
+ * {@link AbstractPayloadTransformer} that delegates to a codec to encode the
+ * payload into a byte[].
+ *
+ * @author Gary Russell
+ * @since 4.2
+ *
+ */
+public class EncodingPayloadTransformer<T> extends AbstractPayloadTransformer<T, byte[]> {
+
+	private final Codec codec;
+
+	public EncodingPayloadTransformer(Codec codec) {
+		Assert.notNull(codec, "'codec' cannot be null");
+		this.codec = codec;
+	}
+
+	@Override
+	protected byte[] transformPayload(T payload) throws Exception {
+		return codec.encode(payload);
+	}
+
+}

spring-integration-core/src/test/java/org/springframework/integration/transformer/CodecTransformerTests.java

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+/*
+ * Copyright 2015 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.integration.transformer;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.Collections;
+
+import org.junit.Test;
+
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.springframework.integration.codec.Codec;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.GenericMessage;
+
+/**
+ * @author Gary Russell
+ * @since 4.2
+ *
+ */
+public class CodecTransformerTests {
+
+	@Test
+	public void testCodec() throws Exception {
+		MyCodec codec = new MyCodec();
+		EncodingPayloadTransformer<String> enc = new EncodingPayloadTransformer<String>(codec);
+		Message<?> message = new GenericMessage<String>("bar");
+		byte[] transformed = enc.doTransform(message);
+		assertArrayEquals("foo".getBytes(), transformed);
+		DecodingTransformer<?> dec = new DecodingTransformer<String>(codec, String.class);
+		assertEquals("foo", dec.doTransform(new GenericMessage<byte[]>(transformed)));
+
+		dec = new DecodingTransformer<Integer>(codec, new SpelExpressionParser().parseExpression("T(Integer)"));
+		dec.setEvaluationContext(new StandardEvaluationContext());
+		assertEquals(42, dec.doTransform(new GenericMessage<byte[]>(transformed)));
+
+		dec = new DecodingTransformer<Integer>(codec, new SpelExpressionParser().parseExpression("headers['type']"));
+		dec.setEvaluationContext(new StandardEvaluationContext());
+		assertEquals(42, dec.doTransform(new GenericMessage<byte[]>(transformed,
+				Collections.singletonMap("type", Integer.class))));
+	}
+
+	public static class MyCodec implements Codec {
+
+		@Override
+		public void encode(Object object, OutputStream outputStream) throws IOException {
+		}
+
+		@Override
+		public byte[] encode(Object object) throws IOException {
+			return "foo".getBytes();
+		}
+
+		@Override
+		public <T> T decode(InputStream inputStream, Class<T> type) throws IOException {
+			return null;
+		}
+
+		@SuppressWarnings("unchecked")
+		@Override
+		public <T> T decode(byte[] bytes, Class<T> type) throws IOException {
+			return (T) (type.equals(String.class) ? new String(bytes) :
+				type.equals(Integer.class) ? Integer.valueOf(42) : Integer.valueOf(43));
+		}
+
+	}
+
+}