JSON content and JsonPath support for WebTestClient

Issue: SPR-15420

spring-test/src/main/java/org/springframework/test/web/reactive/server/DefaultWebTestClient.java

@@ -40,6 +40,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.reactive.ClientHttpConnector;
 import org.springframework.http.client.reactive.ClientHttpRequest;
+import org.springframework.test.util.JsonExpectationsHelper;
 import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
 import org.springframework.util.MultiValueMap;
@@ -502,6 +503,24 @@ class DefaultWebTestClient implements WebTestClient {
 			return new EntityExchangeResult<>(this.result, null);
 		}
 
+		@Override
+		public BodyContentSpec json(String json) {
+			this.result.assertWithDiagnostics(() -> {
+				try {
+					new JsonExpectationsHelper().assertJsonEqual(json, getBodyAsString());
+				}
+				catch (Exception ex) {
+					throw new AssertionError("JSON parsing error", ex);
+				}
+			});
+			return this;
+		}
+
+		@Override
+		public JsonPathAssertions jsonPath(String expression, Object... args) {
+			return new JsonPathAssertions(this, expression, args);
+		}
+
 		@Override
 		public BodyContentSpec consumeAsStringWith(Consumer<String> consumer) {
 			this.result.assertWithDiagnostics(() -> consumer.accept(getBodyAsString()));

spring-test/src/main/java/org/springframework/test/web/reactive/server/JsonPathAssertions.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2002-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.test.web.reactive.server;
+
+import org.springframework.test.util.JsonPathExpectationsHelper;
+
+
+/**
+ * <a href="https://github.com/jayway/JsonPath">JsonPath</a> assertions.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.0
+ * @see <a href="https://github.com/jayway/JsonPath">https://github.com/jayway/JsonPath</a>
+ */
+public class JsonPathAssertions {
+
+	private final WebTestClient.BodyContentSpec bodySpec;
+
+	private final JsonPathExpectationsHelper pathHelper;
+
+
+	JsonPathAssertions(WebTestClient.BodyContentSpec spec, String expression, Object... args) {
+		this.bodySpec = spec;
+		this.pathHelper = new JsonPathExpectationsHelper(expression, args);
+	}
+
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValue(String, Object)}.
+	 */
+	public WebTestClient.BodyContentSpec isEqualTo(Object expectedValue) {
+		this.bodySpec.consumeAsStringWith(body -> {
+			this.pathHelper.assertValue(body, expectedValue);
+		});
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#exists(String)}.
+	 */
+	public WebTestClient.BodyContentSpec exists() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::exists);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#doesNotExist(String)}.
+	 */
+	public WebTestClient.BodyContentSpec doesNotExist() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::doesNotExist);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsEmpty(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isEmpty() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsEmpty);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsNotEmpty(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isNotEmpty() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsNotEmpty);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsBoolean(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isBoolean() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsBoolean);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsNumber(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isNumber() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsNumber);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsArray(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isArray() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsArray);
+		return this.bodySpec;
+	}
+
+	/**
+	 * Applies {@link JsonPathExpectationsHelper#assertValueIsMap(String)}.
+	 */
+	public WebTestClient.BodyContentSpec isMap() {
+		this.bodySpec.consumeAsStringWith(this.pathHelper::assertValueIsMap);
+		return this.bodySpec;
+	}
+
+}

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -598,11 +598,31 @@ public interface WebTestClient {
 	interface BodyContentSpec {
 
 		/**
-		 * Consume the body and verify it is empty.
-		 * @return the exchange result
+		 * Assert the response body is empty and return the exchange result.
 		 */
 		EntityExchangeResult<Void> isEmpty();
 
+		/**
+		 * Parse the expected and actual response content as JSON and perform a
+		 * "lenient" comparison verifying the same attribute-value pairs.
+		 * <p>Use of this option requires the
+		 * <a href="http://jsonassert.skyscreamer.org/">JSONassert<a/> library
+		 * on to be on the classpath.
+		 * @param expectedJson the expected JSON content.
+		 */
+		BodyContentSpec json(String expectedJson);
+
+		/**
+		 * Access to response body assertions using a
+		 * <a href="https://github.com/jayway/JsonPath">JsonPath</a> expression
+		 * to inspect a specific subset of the body.
+		 * <p>The JSON path expression can be a parameterized string using
+		 * formatting specifiers as defined in {@link String#format}.
+		 * @param expression the JsonPath expression
+		 * @param args arguments to parameterize the expression
+		 */
+		JsonPathAssertions jsonPath(String expression, Object... args);
+
 		/**
 		 * Assert the response body content converted to a String with the given
 		 * {@link Consumer}. The String is created with the {@link Charset} from