Fix error message for type mismatch in jsonPath().value()

Prior to this commit, if a value existed at the specified JSON path but
had an incompatible type, the AssertionError thrown contained a message
stating that the value did not exist (i.e., "No Value at JSON Path"),
which was not only misleading but also technically incorrect.

This commit fixes the error message for such use cases. For example, the
AssertionError thrown in such use cases now resembles the following.

  At JSON path "$.name", value <Lisa> of type <java.lang.String> cannot
  be converted to type <byte[]>

Closes gh-25480

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

@@ -26,6 +26,7 @@ import org.hamcrest.MatcherAssert;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -108,10 +109,18 @@ public class JsonPathExpectationsHelper {
 			}
 			actualValue = actualValueList.get(0);
 		}
-		else if (actualValue != null && expectedValue != null) {
-			if (!actualValue.getClass().equals(expectedValue.getClass())) {
+		else if (actualValue != null && expectedValue != null &&
+				!actualValue.getClass().equals(expectedValue.getClass())) {
+			try {
 				actualValue = evaluateJsonPath(content, expectedValue.getClass());
 			}
+			catch (AssertionError error) {
+				String message = String.format(
+					"At JSON path \"%s\", value <%s> of type <%s> cannot be converted to type <%s>",
+					this.expression, actualValue, ClassUtils.getDescriptiveType(actualValue),
+					ClassUtils.getDescriptiveType(expectedValue));
+				throw new AssertionError(message, error.getCause());
+			}
 		}
 		AssertionErrors.assertEquals("JSON path \"" + this.expression + "\"", expectedValue, actualValue);
 	}
@@ -298,7 +307,7 @@ public class JsonPathExpectationsHelper {
 
 	/**
 	 * Variant of {@link #evaluateJsonPath(String)} with a target type.
-	 * This can be useful for matching numbers reliably for example coercing an
+	 * <p>This can be useful for matching numbers reliably for example coercing an
 	 * integer into a double.
 	 * @param content the content to evaluate against
 	 * @return the result of the evaluation

spring-test/src/test/java/org/springframework/test/web/servlet/result/JsonPathResultMatchersTests.java

@@ -64,9 +64,17 @@ public class JsonPathResultMatchersTests {
 	}
 
 	@Test
-	public void valueWithMismatch() throws Exception {
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() ->
-				new JsonPathResultMatchers("$.str").value("bogus").match(stubMvcResult));
+	public void valueWithValueMismatch() throws Exception {
+		assertThatExceptionOfType(AssertionError.class)
+			.isThrownBy(() -> new JsonPathResultMatchers("$.str").value("bogus").match(stubMvcResult))
+			.withMessage("JSON path \"$.str\" expected:<bogus> but was:<foo>");
+	}
+
+	@Test
+	public void valueWithTypeMismatch() throws Exception {
+		assertThatExceptionOfType(AssertionError.class)
+			.isThrownBy(() -> new JsonPathResultMatchers("$.str").value("bogus".getBytes()).match(stubMvcResult))
+			.withMessage("At JSON path \"$.str\", value <foo> of type <java.lang.String> cannot be converted to type <byte[]>");
 	}
 
 	@Test