Configure JsonPath in RestTestClient with MappingProvider

Closes gh-35793

Author: rstoyanchev

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClient.java

@@ -28,9 +28,13 @@
 import java.util.function.Consumer;
 import java.util.function.Function;
 
+import com.jayway.jsonpath.Configuration;
+import com.jayway.jsonpath.TypeRef;
+import com.jayway.jsonpath.spi.mapper.MappingProvider;
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.ResolvableType;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRequest;
@@ -486,7 +490,8 @@ public BodyContentSpec xml(String expectedXml) {
 
 		@Override
 		public JsonPathAssertions jsonPath(String expression) {
-			return new JsonPathAssertions(this, getBodyAsString(), expression, null);
+			Configuration config = JsonPathConfigurationProvider.getConfiguration(this.result);
+			return new JsonPathAssertions(this, getBodyAsString(), expression, config);
 		}
 
 		@Override
@@ -540,4 +545,37 @@ public byte[] getRequestContent(String requestId) {
 		}
 	}
 
+
+	private static class JsonPathConfigurationProvider {
+
+		static Configuration getConfiguration(EntityExchangeResult<?> result) {
+			Configuration config = Configuration.defaultConfiguration();
+			JsonConverterDelegate delegate = result.getJsonConverterDelegate();
+			return (delegate != null ? config.mappingProvider(new MessageConverterMappingProvider(delegate)) : config);
+		}
+	}
+
+
+	private record MessageConverterMappingProvider(JsonConverterDelegate delegate) implements MappingProvider {
+
+		@Override
+		public <T> T map(Object value, Class<T> targetType, Configuration configuration) {
+			return mapToTargetType(value, ResolvableType.forClass(targetType));
+		}
+
+		@Override
+		public <T> T map(Object value, TypeRef<T> targetType, Configuration configuration) {
+			return mapToTargetType(value, ResolvableType.forType(targetType.getType()));
+		}
+
+		private <T> T mapToTargetType(Object value, ResolvableType targetType) {
+			try {
+				return delegate().map(value, targetType);
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException("Failed to map " + value + " to " + targetType, ex);
+			}
+		}
+	}
+
 }

spring-test/src/test/java/org/springframework/test/web/servlet/client/JsonPathAssertionTests.java

@@ -23,6 +23,7 @@
 import org.hamcrest.MatcherAssert;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.test.web.Person;
@@ -106,6 +107,19 @@ void equality() {
 				.jsonPath("$.performers[1].name").value(v -> MatcherAssert.assertThat(v, equalTo("Yehudi Menuhin")));
 	}
 
+	@Test
+	void valueConsumer() {
+		client.get().uri("/music/people")
+				.exchange()
+				.expectBody()
+				.jsonPath("$.composers[0].name").value(
+						String.class,
+						name -> assertThat(name).isEqualTo("Johann Sebastian Bach"))
+				.jsonPath("$.composers[0].name").value(
+						ParameterizedTypeReference.forType(String.class),
+						name -> assertThat(name).isEqualTo("Johann Sebastian Bach"));
+	}
+
 	@Test
 	void hamcrestMatcher() {
 		client.get().uri("/music/people")