DATACMNS-139 - Fixed potential StackOverflowException in PropertyPath.

When trying to access an inexistent property starting with an underscore (e.g. _id) PropertyPath.create(…) ran into a StackOverflowException. Changed the traversing regular expression to expect at least one capital letter for further traversals.

spring-data-commons-core/src/main/java/org/springframework/data/mapping/PropertyPath.java

@@ -321,7 +321,7 @@ public class PropertyPath implements Iterable<PropertyPath> {
 			exception = e;
 		}
 
-		Pattern pattern = Pattern.compile("[A-Z]?[a-z]*$");
+		Pattern pattern = Pattern.compile("[A-Z]+[a-z]*$");
 		Matcher matcher = pattern.matcher(source);
 
 		if (matcher.find() && matcher.start() != 0) {

spring-data-commons-core/src/test/java/org/springframework/data/mapping/PropertyUnitTests.java

@@ -18,14 +18,11 @@ package org.springframework.data.mapping;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
-import java.util.ArrayList;
 import java.util.Iterator;
-import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
 import org.junit.Test;
-import org.springframework.data.mapping.PropertyPath;
 
 /**
  * Unit tests for {@link PropertyPath}.
@@ -169,6 +166,45 @@ public class PropertyUnitTests {
 		assertThat(iterator.hasNext(), is(false));
 	}
 
+	/**
+	 * @see DATACMNS-139
+	 */
+	@Test
+	public void rejectsInvalidPropertyWithLeadingUnderscore() {
+		try {
+			PropertyPath.from("_id", Foo.class);
+			fail();
+		} catch (IllegalArgumentException e) {
+			assertThat(e.getMessage(), containsString("property _id"));
+		}
+	}
+
+	/**
+	 * @see DATACMNS-139
+	 */
+	@Test
+	public void rejectsNestedInvalidPropertyWithLeadingUnderscore() {
+		try {
+			PropertyPath.from("_foo_id", Sample2.class);
+			fail();
+		} catch (IllegalArgumentException e) {
+			assertThat(e.getMessage(), containsString("property id"));
+		}
+	}
+
+	/**
+	 * @see DATACMNS-139
+	 */
+	@Test
+	public void rejectsNestedInvalidPropertyExplictlySplitWithLeadingUnderscore() {
+		try {
+			PropertyPath.from("_foo__id", Sample2.class);
+			fail();
+		} catch (IllegalArgumentException e) {
+			assertThat(e.getMessage(), containsString("property _id"));
+		}
+	}
+
 	private class Foo {
 
 		String userName;