Skip "data:" lines without content

Closes gh-27923

spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -42,6 +42,7 @@ import org.springframework.lang.Nullable;
  *
  * @author Sebastien Deleuze
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 5.0
  */
 public class ServerSentEventHttpMessageReader implements HttpMessageReader<Object> {
@@ -140,22 +141,23 @@ public class ServerSentEventHttpMessageReader implements HttpMessageReader<Objec
 	private Object buildEvent(List<String> lines, ResolvableType valueType, boolean shouldWrap,
 			Map<String, Object> hints) {
 
-		ServerSentEvent.Builder<Object> sseBuilder = shouldWrap ? ServerSentEvent.builder() : null;
+		ServerSentEvent.Builder<Object> sseBuilder = (shouldWrap ? ServerSentEvent.builder() : null);
 		StringBuilder data = null;
 		StringBuilder comment = null;
 
 		for (String line : lines) {
 			if (line.startsWith("data:")) {
-				data = (data != null ? data : new StringBuilder());
+				int length = line.length();
-				if (line.charAt(5) != ' ') {
+				if (length > 5) {
-					data.append(line, 5, line.length());
+					int index = (line.charAt(5) != ' ' ? 5 : 6);
+					if (length > index) {
+						data = (data != null ? data : new StringBuilder());
+						data.append(line, index, line.length());
+						data.append('\n');
+					}
 				}
-				else {
-					data.append(line, 6, line.length());
-				}
-				data.append('\n');
 			}
-			if (shouldWrap) {
+			else if (shouldWrap) {
 				if (line.startsWith("id:")) {
 					sseBuilder.id(line.substring(3).trim());
 				}

spring-web/src/test/java/org/springframework/http/codec/ServerSentEventHttpMessageReaderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -40,6 +40,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Unit tests for {@link ServerSentEventHttpMessageReader}.
  *
  * @author Sebastien Deleuze
+ * @author Juergen Hoeller
  */
 public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingTests {
 
@@ -66,7 +67,7 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 		MockServerHttpRequest request = MockServerHttpRequest.post("/")
 				.body(Mono.just(stringBuffer(
 						"id:c42\nevent:foo\nretry:123\n:bla\n:bla bla\n:bla bla bla\ndata:bar\n\n" +
-						"id:c43\nevent:bar\nretry:456\ndata:baz\n\n")));
+						"id:c43\nevent:bar\nretry:456\ndata:baz\n\ndata:\n\ndata: \n\n")));
 
 		Flux<ServerSentEvent> events = this.reader
 				.read(ResolvableType.forClassWithGenerics(ServerSentEvent.class, String.class),
@@ -87,6 +88,8 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 					assertThat(event.comment()).isNull();
 					assertThat(event.data()).isEqualTo("baz");
 				})
+				.consumeNextWith(event -> assertThat(event.data()).isNull())
+				.consumeNextWith(event -> assertThat(event.data()).isNull())
 				.expectComplete()
 				.verify();
 	}
@@ -175,7 +178,7 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 				.verify();
 	}
 
-	@Test // gh-24389
+	@Test  // gh-24389
 	void readPojoWithCommentOnly() {
 		MockServerHttpRequest request = MockServerHttpRequest.post("/")
 				.body(Flux.just(stringBuffer(":ping\n"), stringBuffer("\n")));
@@ -221,7 +224,6 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 
 	@Test
 	public void maxInMemoryLimit() {
-
 		this.reader.setMaxInMemorySize(17);
 
 		MockServerHttpRequest request = MockServerHttpRequest.post("/")
@@ -235,9 +237,8 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 				.verify();
 	}
 
-	@Test // gh-24312
+	@Test  // gh-24312
 	public void maxInMemoryLimitAllowsReadingPojoLargerThanDefaultSize() {
-
 		int limit = this.jsonDecoder.getMaxInMemorySize();
 
 		String fooValue = getStringOfSize(limit) + "and then some more";
@@ -259,13 +260,6 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 				.verify();
 	}
 
-	private static String getStringOfSize(long size) {
-		StringBuilder content = new StringBuilder("Aa");
-		while (content.length() < size) {
-			content.append(content);
-		}
-		return content.toString();
-	}
 
 	private DataBuffer stringBuffer(String value) {
 		byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
@@ -274,4 +268,12 @@ public class ServerSentEventHttpMessageReaderTests extends AbstractLeakCheckingT
 		return buffer;
 	}
 
+	private static String getStringOfSize(long size) {
+		StringBuilder content = new StringBuilder("Aa");
+		while (content.length() < size) {
+			content.append(content);
+		}
+		return content.toString();
+	}
+
 }