Use a SimpleJsonSerializer in the FileSplitter (#3262)

* Use a SimpleJsonSerializer in the FileSplitter

* To avoid extra dependency for Jackson when we
serialize `FileSplitter.FileMarker` to JSON, use
a `SimpleJsonSerializer` instead.
* Fix `SimpleJsonSerializer` to escape a `\` symbol from property values
since it is used for quoting string values in the final JSON

* * Document the change

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/json/SimpleJsonSerializer.java

@@ -22,6 +22,7 @@
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.regex.Matcher;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -99,7 +100,7 @@ private static String toElement(Object result) {
 			return result.toString();
 		}
 		else {
-			return "\"" + (result == null ? "null" : result.toString()) + "\"";
+			return "\"" + (result == null ? "null" : Matcher.quoteReplacement(result.toString())) + "\"";
 		}
 	}
 

spring-integration-file/src/main/java/org/springframework/integration/file/splitter/FileSplitter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2019 the original author or authors.
+ * Copyright 2015-2020 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.
@@ -37,11 +37,11 @@
 import org.springframework.integration.StaticMessageHeaderAccessor;
 import org.springframework.integration.file.FileHeaders;
 import org.springframework.integration.file.splitter.FileSplitter.FileMarker.Mark;
+import org.springframework.integration.json.SimpleJsonSerializer;
 import org.springframework.integration.splitter.AbstractMessageSplitter;
 import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
-import org.springframework.integration.support.json.JsonObjectMapper;
-import org.springframework.integration.support.json.JsonObjectMapperProvider;
 import org.springframework.integration.util.CloseableIterator;
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandlingException;
 import org.springframework.util.Assert;
@@ -75,15 +75,13 @@
  */
 public class FileSplitter extends AbstractMessageSplitter {
 
-	private static final JsonObjectMapper<?, ?> OBJECT_MAPPER =
-			JsonObjectMapperProvider.jsonAvailable() ? JsonObjectMapperProvider.newInstance() : null;
-
 	private final boolean returnIterator;
 
 	private final boolean markers;
 
 	private final boolean markersJson;
 
+	@Nullable
 	private Charset charset;
 
 	private String firstLineHeaderName;
@@ -129,19 +127,14 @@ public FileSplitter(boolean iterator, boolean markers) {
 	 * @param iterator true to return an iterator, false to return a list of lines.
 	 * @param markers true to emit start of file/end of file marker messages before/after
 	 * the data.
-	 * @param markersJson when true, markers are represented as JSON - requires a
-	 * supported JSON implementation on the classpath. See
-	 * {@link JsonObjectMapperProvider} for supported implementations.
+	 * @param markersJson when true, markers are represented as JSON.
 	 * @since 4.2.7
 	 */
 	public FileSplitter(boolean iterator, boolean markers, boolean markersJson) {
 		this.returnIterator = iterator;
 		this.markers = markers;
 		if (markers) {
 			setApplySequence(false);
-			if (markersJson) {
-				Assert.notNull(OBJECT_MAPPER, "'markersJson' requires an object mapper");
-			}
 		}
 		this.markersJson = markersJson;
 	}
@@ -151,7 +144,7 @@ public FileSplitter(boolean iterator, boolean markers, boolean markersJson) {
 	 * charset is required.
 	 * @param charset the charset.
 	 */
-	public void setCharset(Charset charset) {
+	public void setCharset(@Nullable Charset charset) {
 		this.charset = charset;
 	}
 
@@ -410,7 +403,7 @@ private AbstractIntegrationMessageBuilder<Object> markerToReturn(FileMarker file
 			Object payload;
 			if (FileSplitter.this.markersJson) {
 				try {
-					payload = OBJECT_MAPPER.toJson(fileMarker);
+					payload = SimpleJsonSerializer.toJson(fileMarker);
 				}
 				catch (Exception e) {
 					throw new MessageHandlingException(this.message, "Failed to convert marker to JSON", e);
@@ -489,7 +482,6 @@ public String toString() {
 			}
 		}
 
-
 	}
 
 }

spring-integration-file/src/test/java/org/springframework/integration/file/splitter/FileSplitterTests.java

@@ -31,6 +31,7 @@
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.Date;
+import java.util.List;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -50,6 +51,7 @@
 import org.springframework.integration.file.FileHeaders;
 import org.springframework.integration.file.splitter.FileSplitter.FileMarker;
 import org.springframework.integration.handler.advice.IdempotentReceiverInterceptor;
+import org.springframework.integration.json.JsonPathUtils;
 import org.springframework.integration.metadata.ConcurrentMetadataStore;
 import org.springframework.integration.metadata.SimpleMetadataStore;
 import org.springframework.integration.selector.MetadataStoreSelector;
@@ -248,6 +250,7 @@ void testMarkersEmptyFile() throws IOException {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	void testMarkersJson() throws Exception {
 		JsonObjectMapper<?, ?> objectMapper = JsonObjectMapperProvider.newInstance();
 		QueueChannel outputChannel = new QueueChannel();
@@ -260,7 +263,8 @@ void testMarkersJson() throws Exception {
 		assertThat(received.getHeaders().get(FileHeaders.MARKER)).isEqualTo("START");
 		assertThat(received.getPayload()).isInstanceOf(String.class);
 		String payload = (String) received.getPayload();
-		assertThat(payload).contains("\"mark\":\"START\",\"lineCount\":0");
+		assertThat((List<String>) JsonPathUtils.evaluate(payload, "$..mark")).hasSize(1).contains("START");
+		assertThat((List<Integer>) JsonPathUtils.evaluate(payload, "$..lineCount")).hasSize(1).contains(0);
 		FileMarker fileMarker = objectMapper.fromJson(payload, FileSplitter.FileMarker.class);
 		assertThat(fileMarker.getMark()).isEqualTo(FileSplitter.FileMarker.Mark.START);
 		assertThat(fileMarker.getFilePath()).isEqualTo(file.getAbsolutePath());

src/reference/asciidoc/file.adoc

@@ -1016,7 +1016,7 @@ The default is `false`.
 When `true`, `apply-sequence` is `false` by default.
 See also `markers-json` (the next attribute).
 <4> When `markers` is true, set this to `true` to have the `FileMarker` objects be converted to a JSON string.
-Requires a supported JSON processor library (e.g. Jackson) on the classpath.
+(Uses a `SimpleJsonSerializer` underneath).
 <5> Set to `false` to disable the inclusion of `sequenceSize` and `sequenceNumber` headers in messages.
 The default is `true`, unless `markers` is `true`.
 When `true` and `markers` is `true`, the markers are included in the sequencing.
@@ -1050,7 +1050,7 @@ public FileSplitter(boolean iterator, boolean markers, boolean markersJson)
 ----
 ====
 
-When `markersJson` is true, the markers are represented as a JSON string, as long as a suitable JSON processor library (e.g Jackson) is on the classpath.
+When `markersJson` is true, the markers are represented as a JSON string (using a `SimpleJsonSerializer`).
 
 Version 5.0 introduced the `firstLineAsHeader` option to specify that the first line of content is a header (such as column names in a CSV file).
 The argument passed to this property is the header name under which the first line is carried as a header in the messages emitted for the remaining lines.

src/reference/asciidoc/whats-new.adoc

@@ -158,3 +158,10 @@ See <<./mqtt.adoc#mqtt-events,MQTT Events>>.
 
 The `FileTransferringMessageHandler` (for FTP and SFTP, for example) in addition to `File`, `byte[]`, `String` and `InputStream` now also supports an `org.springframework.core.io.Resource`.
 See <<./sftp.adoc#sftp,SFTP Support>> and <<./ftp.adoc#ftp,FTP Support>> for more information.
+
+[[x5.3-file]]
+=== File Changes
+
+The `FileSplitter` doesn't require a Jackson processor (or similar) dependency any more for the `markersJson` mode.
+It uses a `SimpleJsonSerializer` for a straightforward string representation of the `FileSplitter.FileMarker` instances.
+See <<./file.adoc#file-splitter,FileSplitter>> for more information.