Add remove json attributes filter (#2742)

* Add RemoveJsonAttributesFilterFactory
Takes a collection of attribute names to search for to remove from a JSON response, an optional last parameter from the list can be a boolean to remove the attributes just at root level or recursively

* Add docs for RemoveJsonAttributes filter

* Extract a single instance of Json mapper

* Overload boolean parameter to avoid parsing a string

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -1118,6 +1118,51 @@ spring:
 
 This will send a status 302 with a `Location:https://acme.org` header to perform a redirect.
 
+=== `RemoveJsonAttributesResponseBody` `GatewayFilter` Factory
+
+The `RemoveJsonAttributesResponseBody` `GatewayFilter` factory takes a collection of `attribute names` to search for, an optional last parameter from the list can be a boolean to remove the attributes just at root level (that's the default value if not present at the end of the parameter configuration, `false`) or recursively (`true`).
+It provides a convenient method to apply a transformation to JSON body content by deleting attributes from it.
+
+The following example configures an `RemoveJsonAttributesResponseBody` `GatewayFilter`:
+
+.application.yml
+====
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: removejsonattributes_route
+        uri: https://example.org
+        filters:
+        - RemoveJsonAttributesResponseBody=id,color
+----
+====
+
+This removes attributes "id" and "color" from the JSON content body at root level.
+
+The following example configures an `RemoveJsonAttributesResponseBody` `GatewayFilter` that uses the optional last parameter:
+
+.application.yml
+====
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: removejsonattributes_recursively_route
+        uri: https://example.org
+        predicates:
+        - Path=/red/{segment}
+        filters:
+        - RemoveJsonAttributesResponseBody=id,color,true
+----
+====
+
+This removes attributes "id" and "color" from the JSON content body at any level.
+
 === The `RemoveRequestHeader` GatewayFilter Factory
 
 The `RemoveRequestHeader` `GatewayFilter` factory takes a `name` parameter.

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -79,6 +79,7 @@ import org.springframework.cloud.gateway.filter.factory.MapRequestHeaderGatewayF
 import org.springframework.cloud.gateway.filter.factory.PrefixPathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.PreserveHostHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RedirectToGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RemoveJsonAttributesResponseBodyGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestParameterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
@@ -549,6 +550,15 @@ public class GatewayAutoConfiguration {
 		return new RedirectToGatewayFilterFactory();
 	}
 
+	@Bean
+	@ConditionalOnEnabledFilter
+	public RemoveJsonAttributesResponseBodyGatewayFilterFactory removeJsonAttributesResponseBodyGatewayFilterFactory(
+			ServerCodecConfigurer codecConfigurer, Set<MessageBodyDecoder> bodyDecoders,
+			Set<MessageBodyEncoder> bodyEncoders) {
+		return new RemoveJsonAttributesResponseBodyGatewayFilterFactory(
+				new ModifyResponseBodyGatewayFilterFactory(codecConfigurer.getReaders(), bodyDecoders, bodyEncoders));
+	}
+
 	@Bean
 	@ConditionalOnEnabledFilter
 	public RemoveRequestHeaderGatewayFilterFactory removeRequestHeaderGatewayFilterFactory() {

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/factory/RemoveJsonAttributesResponseBodyGatewayFilterFactory.java

@@ -0,0 +1,147 @@
+/*
+ * Copyright 2013-2020 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
+ *
+ *      https://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.cloud.gateway.filter.factory;
+
+import java.util.Arrays;
+import java.util.List;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import reactor.core.publisher.Mono;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.factory.rewrite.ModifyResponseBodyGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.rewrite.RewriteFunction;
+import org.springframework.core.style.ToStringCreator;
+import org.springframework.http.MediaType;
+
+/**
+ * @author Marta Medio
+ */
+public class RemoveJsonAttributesResponseBodyGatewayFilterFactory extends
+		AbstractGatewayFilterFactory<RemoveJsonAttributesResponseBodyGatewayFilterFactory.FieldListConfiguration> {
+
+	public RemoveJsonAttributesResponseBodyGatewayFilterFactory(
+			ModifyResponseBodyGatewayFilterFactory modifyResponseBodyGatewayFilterFactory) {
+		this.modifyResponseBodyGatewayFilterFactory = modifyResponseBodyGatewayFilterFactory;
+	}
+
+	@Override
+	public ShortcutType shortcutType() {
+		return ShortcutType.GATHER_LIST_TAIL_FLAG;
+	}
+
+	@Override
+	public List<String> shortcutFieldOrder() {
+		return Arrays.asList("fieldList", "deleteRecursively");
+	}
+
+	@Override
+	public FieldListConfiguration newConfig() {
+		return new FieldListConfiguration();
+	}
+
+	@Override
+	public Class<FieldListConfiguration> getConfigClass() {
+		return FieldListConfiguration.class;
+	}
+
+	@Override
+	public GatewayFilter apply(FieldListConfiguration config) {
+		ModifyResponseBodyGatewayFilterFactory.Config modifyResponseBodyConfig = new ModifyResponseBodyGatewayFilterFactory.Config();
+		modifyResponseBodyConfig.setInClass(String.class);
+		modifyResponseBodyConfig.setOutClass(String.class);
+
+		RewriteFunction<String, String> rewriteFunction = (exchange, body) -> {
+			if (MediaType.APPLICATION_JSON.isCompatibleWith(exchange.getResponse().getHeaders().getContentType())) {
+				try {
+					JsonNode jsonBodyContent = mapper.readValue(body, JsonNode.class);
+
+					removeJsonAttribute(jsonBodyContent, config.getFieldList(), config.isDeleteRecursively());
+
+					body = mapper.writeValueAsString(jsonBodyContent);
+				}
+				catch (JsonProcessingException e) {
+					throw new RuntimeException(e);
+				}
+			}
+			return Mono.just(body);
+		};
+		modifyResponseBodyConfig.setRewriteFunction(rewriteFunction);
+
+		return modifyResponseBodyGatewayFilterFactory.apply(modifyResponseBodyConfig);
+	}
+
+	private final ModifyResponseBodyGatewayFilterFactory modifyResponseBodyGatewayFilterFactory;
+
+	private ObjectMapper mapper = new ObjectMapper();
+
+	private void removeJsonAttribute(JsonNode jsonBodyContent, List<String> fieldsToRemove, boolean deleteRecursively) {
+		if (deleteRecursively) {
+			for (JsonNode jsonNode : jsonBodyContent) {
+				if (jsonNode instanceof ObjectNode) {
+					((ObjectNode) jsonNode).remove(fieldsToRemove);
+					removeJsonAttribute(jsonNode, fieldsToRemove, true);
+				}
+				if (jsonNode instanceof ArrayNode) {
+					for (JsonNode node : jsonNode) {
+						removeJsonAttribute(node, fieldsToRemove, true);
+					}
+				}
+			}
+		}
+		if (jsonBodyContent instanceof ObjectNode) {
+			((ObjectNode) jsonBodyContent).remove(fieldsToRemove);
+		}
+	}
+
+	public static class FieldListConfiguration {
+
+		private List<String> fieldList;
+
+		private boolean deleteRecursively;
+
+		public boolean isDeleteRecursively() {
+			return deleteRecursively;
+		}
+
+		public FieldListConfiguration setDeleteRecursively(boolean deleteRecursively) {
+			this.deleteRecursively = deleteRecursively;
+			return this;
+		}
+
+		List<String> getFieldList() {
+			return fieldList;
+		}
+
+		public FieldListConfiguration setFieldList(List<String> fieldList) {
+			this.fieldList = fieldList;
+			return this;
+		}
+
+		@Override
+		public String toString() {
+			return new ToStringCreator(this).append("fieldList", fieldList)
+					.append("deleteRecursively", deleteRecursively).toString();
+		}
+
+	}
+
+}

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -51,6 +51,7 @@ import org.springframework.cloud.gateway.filter.factory.MapRequestHeaderGatewayF
 import org.springframework.cloud.gateway.filter.factory.PrefixPathGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.PreserveHostHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RedirectToGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.RemoveJsonAttributesResponseBodyGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestParameterGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveResponseHeaderGatewayFilterFactory;
@@ -464,6 +465,19 @@ public class GatewayFilterSpec extends UriSpec {
 		}
 	}
 
+	/**
+	 * A filter that can be used to modify the response body.
+	 * @param attributes list of attributes to remove separated by commas, an optional
+	 * last parameter from the list can be a boolean to remove the attributes just at root
+	 * level (false) o recursively (true)
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec removeJsonAttributes(boolean deleteRecursively, String... attributes) {
+		return filter(getBean(RemoveJsonAttributesResponseBodyGatewayFilterFactory.class)
+				.apply(c -> c.setFieldList(Arrays.asList(attributes)).setDeleteRecursively(deleteRecursively)));
+
+	}
+
 	/**
 	 * A filter that will remove a request header before the request is routed by the
 	 * Gateway.

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/filter/factory/RemoveJsonAttributesResponseBodyGatewayFilterFactoryTests.java

@@ -0,0 +1,119 @@
+/*
+ * Copyright 2013-2020 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
+ *
+ *      https://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.cloud.gateway.filter.factory;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.test.annotation.DirtiesContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+import static org.springframework.cloud.gateway.test.TestUtils.getMap;
+
+/**
+ * @author Marta Medio
+ */
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class RemoveJsonAttributesResponseBodyGatewayFilterFactoryTests extends BaseWebClientTests {
+
+	@Test
+	public void removeJsonAttributeRootWorks() {
+		testClient.post().uri("/post").header("Host", "www.removejsonattributes.org")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE).header("foo", "test")
+				.header("bar", "test").exchange().expectStatus().isOk().expectBody(Map.class).consumeWith(result -> {
+					Map<?, ?> response = result.getResponseBody();
+					assertThat(response).isNotNull();
+
+					String responseBody = (String) response.get("data");
+					assertThat(responseBody).isNull();
+
+					Map<String, Object> headers = getMap(response, "headers");
+					assertThat(headers).containsKey("user-agent");
+
+				});
+	}
+
+	@Test
+	public void removeJsonAttributeRecursivelyWorks() {
+
+		testClient.post().uri("/post").header("Host", "www.removejsonattributesrecursively.org")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE).header("foo", "test")
+				.header("bar", "test").exchange().expectStatus().isOk().expectBody(Map.class).consumeWith(result -> {
+					Map<?, ?> response = result.getResponseBody();
+					assertThat(response).isNotNull();
+
+					Map<String, Object> headers = getMap(response, "headers");
+					assertThat(headers).doesNotContainKey("foo");
+					assertThat(headers).containsEntry("bar", "test");
+				});
+	}
+
+	@Test
+	public void removeJsonAttributeNoMatchesWorks() {
+
+		testClient.post().uri("/post").header("Host", "www.removejsonattributesnomatches.org")
+				.header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE).exchange().expectStatus().isOk()
+				.expectBody(Map.class).consumeWith(result -> {
+					Map<?, ?> response = result.getResponseBody();
+					assertThat(response).isNotNull();
+
+					Map<String, Object> headers = getMap(response, "headers");
+					assertThat(headers).isNotNull();
+					assertThat(headers).containsEntry(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
+				});
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+
+		@Value("${test.uri}")
+		String uri;
+
+		@Bean
+		public RouteLocator testRouteLocator(RouteLocatorBuilder builder) {
+			return builder.routes()
+					.route("remove_json_attributes_root_level_java_test",
+							r -> r.path("/post").and().host("{sub}.removejsonattributes.org")
+									.filters(f -> f.removeJsonAttributes(false, "data", "foo")).uri(uri))
+					.route("remove_json_attributes_recursively_java_test",
+							r -> r.path("/post").and().host("{sub}.removejsonattributesrecursively.org")
+									.filters(f -> f.removeJsonAttributes(true, "foo")).uri(uri))
+					.route("remove_json_attributes_no_matches_java_test",
+							r -> r.path("/post").and().host("{sub}.removejsonattributesnomatches.org")
+									.filters(f -> f.removeJsonAttributes(false, "test")).uri(uri))
+					.build();
+		}
+
+	}
+
+}