Protect against Math.abs() with Long.MIN_VALUE

Update RandomValuePropertySource to protect against the random source
returning Long.MIN_VALUE. In such cases the sign bit can't be unset and
prior to this commit the random value stayed negative.

Closes gh-4672

spring-boot/src/main/java/org/springframework/boot/context/config/RandomValuePropertySource.java

@@ -110,11 +110,11 @@ public class RandomValuePropertySource extends PropertySource<Random> {
 	private long getNextLongInRange(String range) {
 		String[] tokens = StringUtils.commaDelimitedListToStringArray(range);
 		if (tokens.length == 1) {
-			return Math.abs(getSource().nextLong()) % Long.parseLong(tokens[0]);
+			return Math.abs(getSource().nextLong() % Long.parseLong(tokens[0]));
 		}
 		long lowerBound = Long.parseLong(tokens[0]);
 		long upperBound = Long.parseLong(tokens[1]) - lowerBound;
-		return lowerBound + Math.abs(getSource().nextLong()) % upperBound;
+		return lowerBound + Math.abs(getSource().nextLong() % upperBound);
 	}
 
 	private Object getRandomBytes() {

spring-boot/src/test/java/org/springframework/boot/context/config/RandomValuePropertySourceTests.java

@@ -16,7 +16,10 @@
 
 package org.springframework.boot.context.config;
 
+import java.util.Random;
+
 import org.junit.Test;
+import org.mockito.Mockito;
 
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
@@ -83,4 +86,27 @@ public class RandomValuePropertySourceTests {
 		assertNotNull(value);
 		assertTrue(value < 10L);
 	}
+
+	@Test
+	public void longOverflow() {
+		RandomValuePropertySource source = Mockito.spy(this.source);
+		Mockito.when(source.getSource()).thenReturn(new Random() {
+
+			@Override
+			public long nextLong() {
+				// constant that used to become -8, now becomes 8
+				return Long.MIN_VALUE;
+			}
+
+		});
+		Long value = (Long) source.getProperty("random.long(10)");
+		assertNotNull(value);
+		assertTrue(value + " is less than 0", value >= 0L);
+		assertTrue(value + " is more than 10", value < 10L);
+
+		value = (Long) source.getProperty("random.long[4,10]");
+		assertNotNull(value);
+		assertTrue(value + " is less than 4", value >= 4L);
+		assertTrue(value + " is more than 10", value < 10L);
+	}
 }