Fix code smell for PayloadTypeConvertTransformers

Author: artembilan

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.integration.transformer;
 
-import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.serializer.Deserializer;
 import org.springframework.integration.support.converter.WhiteListDeserializingConverter;
 import org.springframework.util.Assert;
@@ -31,19 +30,20 @@
  *
  * @author Mark Fisher
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 1.0.1
  */
 public class PayloadDeserializingTransformer extends PayloadTypeConvertingTransformer<byte[], Object> {
 
-
+	/**
+	 * Instantiate based on the {@link WhiteListDeserializingConverter} with the
+	 * {@link org.springframework.core.serializer.DefaultDeserializer}.
+	 */
 	public PayloadDeserializingTransformer() {
 		doSetConverter(new WhiteListDeserializingConverter());
 	}
 
-	private void doSetConverter(Converter<byte[], Object> converter) {
-		this.converter = converter;
-	}
-
 	public void setDeserializer(Deserializer<Object> deserializer) {
 		setConverter(new WhiteListDeserializingConverter(deserializer));
 	}
@@ -58,14 +58,9 @@ public void setDeserializer(Deserializer<Object> deserializer) {
 	 * @since 4.2.13
 	 */
 	public void setWhiteListPatterns(String... patterns) {
-		Assert.isTrue(this.converter instanceof WhiteListDeserializingConverter,
+		Assert.isTrue(getConverter() instanceof WhiteListDeserializingConverter,
 				"Patterns can only be provided when using a 'WhiteListDeserializingConverter'");
-		((WhiteListDeserializingConverter) this.converter).setWhiteListPatterns(patterns);
-	}
-
-	@Override
-	protected Object transformPayload(byte[] payload) throws Exception {
-		return this.converter.convert(payload);
+		((WhiteListDeserializingConverter) getConverter()).setWhiteListPatterns(patterns);
 	}
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -28,20 +28,22 @@
  *
  * @author Mark Fisher
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 1.0.1
  */
 public class PayloadSerializingTransformer extends PayloadTypeConvertingTransformer<Object, byte[]> {
 
-	public void setSerializer(Serializer<Object> serializer) {
-		this.setConverter(new SerializingConverter(serializer));
+	/**
+	 * Instantiate based on the {@link SerializingConverter} with the
+	 * {@link org.springframework.core.serializer.DefaultSerializer}.
+	 */
+	public PayloadSerializingTransformer() {
+		doSetConverter(new SerializingConverter());
 	}
 
-	@Override
-	protected byte[] transformPayload(Object payload) throws Exception {
-		if (this.converter == null) {
-			this.setConverter(new SerializingConverter());
-		}
-		return this.converter.convert(payload);
+	public void setSerializer(Serializer<Object> serializer) {
+		setConverter(new SerializingConverter(serializer));
 	}
 
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -24,24 +24,42 @@
  * Converter<Object, Object>. A reference to the delegate must be provided.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 2.0
  */
 public class PayloadTypeConvertingTransformer<T, U> extends AbstractPayloadTransformer<T, U> {
 
-	protected Converter<T, U> converter;
+	private Converter<T, U> converter;
 
 	/**
 	 * Specify the converter to use.
-	 *
 	 * @param converter The Converter.
 	 */
 	public void setConverter(Converter<T, U> converter) {
+		doSetConverter(converter);
+	}
+
+	protected final void doSetConverter(Converter<T, U> converter) {
+		Assert.notNull(converter, "'converter' must not be null");
 		this.converter = converter;
 	}
+	/**
+	 * Get the configured {@link Converter}.
+	 * @return the converter.
+	 */
+	protected Converter<T, U> getConverter() {
+		return this.converter;
+	}
+
+	@Override
+	protected void onInit() throws Exception {
+		super.onInit();
+		Assert.notNull(this.converter, () -> getClass().getName() + " requires a Converter<Object, Object>");
+	}
 
 	@Override
-	protected U transformPayload(T payload) throws Exception {
-		Assert.notNull(this.converter, this.getClass().getName() + " requires a Converter<Object, Object>");
+	protected U transformPayload(T payload) {
 		return this.converter.convert(payload);
 	}