DATACMNS-381 - Improved exception message in PropertyReferenceException.

PropertyReferenceException now not only exposes the property not found but also the already resolved Property path to make it easier to understand what is causing the exception in the first place.

src/main/java/org/springframework/data/mapping/PropertyPath.java

@@ -18,6 +18,7 @@ package org.springframework.data.mapping;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Stack;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -63,7 +64,7 @@ public class PropertyPath implements Iterable<PropertyPath> {
 	 * @param owningType must not be {@literal null}.
 	 * @param base the {@link PropertyPath} previously found.
 	 */
-	PropertyPath(String name, TypeInformation<?> owningType, PropertyPath base) {
+	PropertyPath(String name, TypeInformation<?> owningType, Stack<PropertyPath> base) {
 
 		Assert.hasText(name);
 		Assert.notNull(owningType);
@@ -264,14 +265,14 @@ public class PropertyPath implements Iterable<PropertyPath> {
 		Iterator<String> parts = iteratorSource.iterator();
 
 		PropertyPath result = null;
-		PropertyPath current = null;
+		Stack<PropertyPath> current = new Stack<PropertyPath>();
 
 		while (parts.hasNext()) {
 			if (result == null) {
-				result = create(parts.next(), type, null);
-				current = result;
+				result = create(parts.next(), type, current);
+				current.push(result);
 			} else {
-				current = create(parts.next(), current);
+				current.push(create(parts.next(), current));
 			}
 		}
 
@@ -285,10 +286,12 @@ public class PropertyPath implements Iterable<PropertyPath> {
 	 * @param base
 	 * @return
 	 */
-	private static PropertyPath create(String source, PropertyPath base) {
+	private static PropertyPath create(String source, Stack<PropertyPath> base) {
 
-		PropertyPath propertyPath = create(source, base.type, base);
-		base.next = propertyPath;
+		PropertyPath previous = base.peek();
+
+		PropertyPath propertyPath = create(source, previous.type, base);
+		previous.next = propertyPath;
 		return propertyPath;
 	}
 
@@ -302,7 +305,7 @@ public class PropertyPath implements Iterable<PropertyPath> {
 	 * @param type
 	 * @return
 	 */
-	private static PropertyPath create(String source, TypeInformation<?> type, PropertyPath base) {
+	private static PropertyPath create(String source, TypeInformation<?> type, Stack<PropertyPath> base) {
 
 		return create(source, type, "", base);
 	}
@@ -317,7 +320,7 @@ public class PropertyPath implements Iterable<PropertyPath> {
 	 * @param addTail
 	 * @return
 	 */
-	private static PropertyPath create(String source, TypeInformation<?> type, String addTail, PropertyPath base) {
+	private static PropertyPath create(String source, TypeInformation<?> type, String addTail, Stack<PropertyPath> base) {
 
 		PropertyReferenceException exception = null;
 		PropertyPath current = null;
@@ -326,8 +329,14 @@ public class PropertyPath implements Iterable<PropertyPath> {
 
 			current = new PropertyPath(source, type, base);
 
+			if (!base.isEmpty()) {
+				base.peek().next = current;
+			}
+
+			base.push(current);
+
 			if (StringUtils.hasText(addTail)) {
-				current.next = create(addTail, current.type, current);
+				current.next = create(addTail, current.type, base);
 			}
 
 			return current;
@@ -355,4 +364,13 @@ public class PropertyPath implements Iterable<PropertyPath> {
 
 		throw exception;
 	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
+	@Override
+	public String toString() {
+		return String.format("%s.%s", owningType.getType().getSimpleName(), toDotPath());
+	}
 }

src/main/java/org/springframework/data/mapping/PropertyReferenceException.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mapping;
 
+import java.util.Stack;
+
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
 
@@ -26,20 +28,20 @@ import org.springframework.util.Assert;
 public class PropertyReferenceException extends RuntimeException {
 
 	private static final long serialVersionUID = -5254424051438976570L;
-	private static final String ERROR_TEMPLATE = "No property %s found for type %s";
+	private static final String ERROR_TEMPLATE = "No property %s found for type %s!";
 
 	private final String propertyName;
 	private final TypeInformation<?> type;
-	private final PropertyPath base;
+	private final Stack<PropertyPath> base;
 
 	/**
 	 * Creates a new {@link PropertyReferenceException}.
 	 * 
 	 * @param propertyName the name of the property not found on the given type.
 	 * @param type the type the property could not be found on.
-	 * @param base the base {@link PropertyPath}.
+	 * @param base the previously calculated {@link PropertyPath}s.
 	 */
-	public PropertyReferenceException(String propertyName, TypeInformation<?> type, PropertyPath base) {
+	public PropertyReferenceException(String propertyName, TypeInformation<?> type, Stack<PropertyPath> base) {
 
 		Assert.hasText(propertyName);
 		Assert.notNull(type);
@@ -73,7 +75,15 @@ public class PropertyReferenceException extends RuntimeException {
 	 */
 	@Override
 	public String getMessage() {
-		return String.format(ERROR_TEMPLATE, propertyName, type.getType().getName());
+
+		StringBuilder builder = new StringBuilder(String.format(ERROR_TEMPLATE, propertyName, type.getType()
+				.getSimpleName()));
+
+		if (!base.isEmpty()) {
+			builder.append(" Traversed path: ").append(base.get(0).toString()).append(".");
+		}
+
+		return builder.toString();
 	}
 
 	/**
@@ -82,6 +92,6 @@ public class PropertyReferenceException extends RuntimeException {
 	 * @return
 	 */
 	public PropertyPath getBaseProperty() {
-		return base;
+		return base.isEmpty() ? null : base.peek();
 	}
 }

src/test/java/org/springframework/data/mapping/PropertyPathUnitTests.java

@@ -36,8 +36,7 @@ import org.springframework.data.util.TypeInformation;
 @SuppressWarnings("unused")
 public class PropertyPathUnitTests {
 
-	@Rule
-	public ExpectedException exception = ExpectedException.none();
+	@Rule public ExpectedException exception = ExpectedException.none();
 
 	@Test
 	@SuppressWarnings("rawtypes")
@@ -307,6 +306,19 @@ public class PropertyPathUnitTests {
 		assertThat(path.next().getSegment(), is("UUID"));
 	}
 
+	/**
+	 * @see DATACMNS-381
+	 */
+	public void exposesPreviouslyReferencedPathInExceptionMessage() {
+
+		exception.expect(PropertyReferenceException.class);
+		exception.expectMessage("bar"); // missing variable
+		exception.expectMessage("String"); // type
+		exception.expectMessage("Bar.user.name"); // previously referenced path
+
+		PropertyPath.from("userNameBar", Bar.class);
+	}
+
 	private class Foo {
 
 		String userName;