Remove dependency on hamcrest-lib from spring-mvc-test

The change removes the use of concrete Matcher implementations and thus
the dependency on hamcrest-lib leaving hamcrest-core as the only
(optional) hamcrest dependency.

Issue: SPR-9961

spring-test/src/main/java/org/springframework/test/util/AssertionErrors.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.test.util;
 
+import org.springframework.util.ObjectUtils;
+
 /**
  * JUnit independent assertion class.
  *
@@ -24,13 +26,14 @@ package org.springframework.test.util;
  */
 public abstract class AssertionErrors {
 
+
     private AssertionErrors() {
     }
 
 	/**
 	 * Fails a test with the given message.
 	 *
-	 * @param message the message
+	 * @param message describes the reason for the failure
 	 */
     public static void fail(String message) {
         throw new AssertionError(message);
@@ -40,17 +43,26 @@ public abstract class AssertionErrors {
 	 * Fails a test with the given message passing along expected and actual
 	 * values to be added to the message.
 	 *
-	 * @param message the message
-	 * @param expected the expected value
-	 * @param actual the actual value
+	 * <p>For example given:
+	 * <pre>
+	 * assertEquals("Response header [" + name + "]", actual, expected);
+	 * </pre>
+	 * <p>The resulting message is:
+	 * <pre>
+	 * Response header [Accept] expected:&lt;application/json&gt; but was:&lt;text/plain&gt;
+	 * </pre>
+	 *
+	 * @param message describes the value that failed the match
+	 * @param expected expected value
+	 * @param actual actual value
 	 */
     public static void fail(String message, Object expected, Object actual) {
         throw new AssertionError(message + " expected:<" + expected + "> but was:<" + actual + ">");
     }
 
 	/**
-	 * Asserts that a condition is {@code true}. If not, throws an
-	 * {@link AssertionError} with the given message.
+	 * Assert the given condition is {@code true} and raise an
+	 * {@link AssertionError} if it is not.
 	 *
 	 * @param message the message
 	 * @param condition the condition to test for
@@ -62,21 +74,20 @@ public abstract class AssertionErrors {
     }
 
 	/**
-	 * Asserts that two objects are equal. If not, an {@link AssertionError} is
-	 * thrown with the given message.
+	 * Assert two objects are equal raise an {@link AssertionError} if not.
+	 * <p>For example:
+	 * <pre>
+	 * assertEquals("Response header [" + name + "]", actual, expected);
+	 * </pre>
 	 *
-	 * @param message the message
+	 * @param message describes the value being checked
 	 * @param expected the expected value
 	 * @param actual the actual value
 	 */
     public static void assertEquals(String message, Object expected, Object actual) {
-        if (expected == null && actual == null) {
-            return;
-        }
-        if (expected != null && expected.equals(actual)) {
-            return;
-        }
-        fail(message, expected, actual);
+		if (!ObjectUtils.nullSafeEquals(expected, actual)) {
+			fail(message, expected, actual);
+		}
     }
 
 }