INT-3503 equals & hashCode for ToStringFriendlyJN

JIRA: https://jira.spring.io/browse/INT-3503

**Cherry-pick to 4.0.x**

PR Comments and test

spring-integration-core/src/main/java/org/springframework/integration/json/JsonPropertyAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2014 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.
@@ -35,14 +35,16 @@ import org.springframework.util.Assert;
  * A SpEL {@link PropertyAccessor} that knows how to read on Jackson JSON objects.
  *
  * @author Eric Bottard
+ * @author Artem Bilan
+ * @since 3.0
  */
 public class JsonPropertyAccessor implements PropertyAccessor {
 
 	/**
 	 * The kind of types this can work with.
 	 */
-	private static final Class<?>[] SUPPORTED_CLASSES = new Class<?>[] { String.class, ToStringFriendlyJsonNode.class,
-			ObjectNode.class, ArrayNode.class };
+	private static final Class<?>[] SUPPORTED_CLASSES = new Class<?>[] {String.class, ToStringFriendlyJsonNode.class,
+			ObjectNode.class, ArrayNode.class};
 
 	// Note: ObjectMapper is thread-safe
 	private ObjectMapper objectMapper = new ObjectMapper();
@@ -144,6 +146,7 @@ public class JsonPropertyAccessor implements PropertyAccessor {
 	}
 
 	public static class ToStringFriendlyJsonNode {
+
 		private final JsonNode node;
 
 		public ToStringFriendlyJsonNode(JsonNode node) {
@@ -159,8 +162,20 @@ public class JsonPropertyAccessor implements PropertyAccessor {
 			else {
 				return node.toString();
 			}
-
 		}
+
+		@Override
+		public boolean equals(Object o) {
+			return this == o
+					|| (!(o == null || getClass() != o.getClass())
+							&& this.node.equals(((ToStringFriendlyJsonNode) o).node));
+		}
+
+		@Override
+		public int hashCode() {
+			return this.node.toString().hashCode();
+		}
+
 	}
 
 }

spring-integration-core/src/test/java/org/springframework/integration/json/JsonPropertyAccessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2014 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.
@@ -17,7 +17,10 @@
 package org.springframework.integration.json;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
+import org.hamcrest.Matchers;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -31,6 +34,8 @@ import com.fasterxml.jackson.databind.ObjectMapper;
  * Tests for {@link JsonPropertyAccessor}.
  *
  * @author Eric Bottard
+ * @author Artem Bilan
+ * @since 3.0
  */
 public class JsonPropertyAccessorTests {
 
@@ -48,8 +53,14 @@ public class JsonPropertyAccessorTests {
 	@Test
 	public void testSimpleLookup() throws Exception {
 		Object json = mapper.readTree("{\"foo\": \"bar\"}");
-		Object actual = evaluate(json, "foo", Object.class);
-		assertEquals("bar", actual.toString());
+		Object value = evaluate(json, "foo", Object.class);
+		assertThat(value, Matchers.instanceOf(JsonPropertyAccessor.ToStringFriendlyJsonNode.class));
+		assertEquals("bar", value.toString());
+		Object json2 = mapper.readTree("{\"foo\": \"bar\"}");
+		Object value2 = evaluate(json2, "foo", Object.class);
+		assertThat(value2, Matchers.instanceOf(JsonPropertyAccessor.ToStringFriendlyJsonNode.class));
+		assertTrue(value.equals(value2));
+		assertEquals(value.hashCode(), value2.hashCode());
 	}
 
 	@Test(expected = SpelEvaluationException.class)