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Centralize Server Sent Event utility methods

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Prior to this commit, many classes would support writing Server Sent
Events in some way to the response output stream. This has lead to some
code duplication.

This commit refactors the duplicated code in a shared `SseUtils` class.

Closes gh-37065
This commit is contained in:
Brian Clozel
2026-08-14 09:11:50 +02:00
parent 062032373e
commit 35921cc01f
9 changed files with 230 additions and 146 deletions
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spring-webmvc/src/main/java/org/springframework/web/servlet/function/SseServerResponse.java
+14 -14
View File
@@ -42,6 +42,7 @@ import org.springframework.util.CollectionUtils;
import org.springframework.util.MultiValueMap;
import org.springframework.web.context.request.async.DeferredResult;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.util.SseUtils;
/**
* Implementation of {@link ServerResponse} for sending
@@ -149,33 +150,35 @@ final class SseServerResponse extends AbstractServerResponse {
@Override
public SseBuilder id(String id) {
Assert.hasLength(id, "Id must not be empty");
return field("id", id);
SseUtils.assertNoLineSeparator(id);
this.builder.append("id:").append(id).append('\n');
return this;
}
@Override
public SseBuilder event(String eventName) {
Assert.hasLength(eventName, "Name must not be empty");
return field("event", eventName);
SseUtils.assertNoLineSeparator(eventName);
this.builder.append("event:").append(eventName).append('\n');
return this;
}
@Override
public SseBuilder retry(Duration duration) {
Assert.notNull(duration, "Duration must not be null");
String millis = Long.toString(duration.toMillis());
return field("retry", millis);
this.builder.append("retry:").append(duration.toMillis()).append('\n');
return this;
}
@Override
public SseBuilder comment(String comment) {
String[] lines = comment.split("\n");
for (String line : lines) {
field("", line);
}
return this;
return field("", comment);
}
private SseBuilder field(String name, String value) {
this.builder.append(name).append(':').append(value).append('\n');
this.builder.append(name).append(':');
SseUtils.appendFieldValue(name, value, this.builder);
this.builder.append('\n');
return this;
}
@@ -191,10 +194,7 @@ final class SseServerResponse extends AbstractServerResponse {
}
private void writeString(String string) throws IOException {
String[] lines = string.split("\n");
for (String line : lines) {
field("data", line);
}
field("data", string);
this.send();
}
spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterReturnValueHandler.java
+2 -19
View File
@@ -66,6 +66,7 @@ import org.springframework.web.servlet.View;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;
import org.springframework.web.servlet.view.FragmentsRendering;
import org.springframework.web.util.SseUtils;
/**
* Handler for return values of type:
@@ -476,26 +477,8 @@ public class ResponseBodyEmitterReturnValueHandler implements HandlerMethodRetur
public byte[] getFragmentContent() {
this.writer.flush();
String content = this.outputStream.toString(this.charset);
if (content.indexOf('\n') == -1 && content.indexOf('\r') == -1) {
return content.getBytes(this.charset);
}
StringBuilder fragment = new StringBuilder();
int length = content.length();
for (int i = 0; i < length; i++) {
char c = content.charAt(i);
if (c == '\r') {
if (i + 1 < length && content.charAt(i + 1) == '\n') {
i++;
}
fragment.append("\ndata:");
}
else if (c == '\n') {
fragment.append("\ndata:");
}
else {
fragment.append(c);
}
}
SseUtils.appendFieldValue("data", content, fragment);
return fragment.toString().getBytes(this.charset);
}
}
spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/SseEmitter.java
+5 -34
View File
@@ -27,10 +27,10 @@ import org.jspecify.annotations.Nullable;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.util.SseUtils;
/**
* A specialization of {@link ResponseBodyEmitter} for sending
@@ -203,14 +203,14 @@ public class SseEmitter extends ResponseBodyEmitter {
@Override
public SseEventBuilder id(String id) {
checkEvent(id);
SseUtils.assertNoLineSeparator(id);
append("id:").append(id).append('\n');
return this;
}
@Override
public SseEventBuilder name(String name) {
checkEvent(name);
SseUtils.assertNoLineSeparator(name);
this.hasName = true;
append("event:").append(name).append('\n');
return this;
@@ -225,7 +225,7 @@ public class SseEmitter extends ResponseBodyEmitter {
@Override
public SseEventBuilder comment(String comment) {
append(':');
appendEscaped(comment, "\n:");
SseUtils.appendFieldValue("", comment, this.sb);
append('\n');
return this;
}
@@ -252,45 +252,16 @@ public class SseEmitter extends ResponseBodyEmitter {
return this;
}
private static void checkEvent(String content) {
Assert.isTrue(content.indexOf('\n') == -1 && content.indexOf('\r') == -1,
"illegal character '\\n' or '\\r' in event content");
}
private void writeStringData(String input, @Nullable MediaType mediaType) {
if (input.indexOf('\n') == -1 && input.indexOf('\r') == -1) {
this.dataToSend.add(new DataWithMediaType(input, mediaType));
}
else {
appendEscaped(input, "\ndata:");
SseUtils.appendFieldValue("data", input, this.sb);
saveAppendedText(mediaType);
}
}
private void appendEscaped(String input, String replacement) {
if (input.indexOf('\n') == -1 && input.indexOf('\r') == -1) {
append(input);
}
else {
int length = input.length();
for (int i = 0; i < length; i++) {
char c = input.charAt(i);
if (c == '\r') {
if (i + 1 < length && input.charAt(i + 1) == '\n') {
i++;
}
append(replacement);
}
else if (c == '\n') {
append(replacement);
}
else {
append(c);
}
}
}
}
SseEventBuilderImpl append(String text) {
this.sb.append(text);
return this;
spring-webmvc/src/test/java/org/springframework/web/servlet/function/SseServerResponseTests.java
+41
View File
@@ -212,6 +212,47 @@ class SseServerResponseTests {
assertThat(this.mockResponse.getContentAsString()).isEqualTo(expected);
}
@Test
void sendStringWithCarriageReturn() throws Exception {
String body = "line1\rline2\r\nline3";
ServerResponse response = ServerResponse.sse(sse -> {
try {
sse.send(body);
}
catch (IOException ex) {
throw new UncheckedIOException(ex);
}
});
ServerResponse.Context context = Collections::emptyList;
ModelAndView mav = response.writeTo(this.mockRequest, this.mockResponse, context);
assertThat(mav).isNull();
String expected = "data:line1\ndata:line2\ndata:line3\n\n";
assertThat(this.mockResponse.getContentAsString()).isEqualTo(expected);
}
@Test
void commentWithCarriageReturn() throws Exception {
ServerResponse response = ServerResponse.sse(sse -> {
try {
sse.comment("line1\rline2").send();
}
catch (IOException ex) {
throw new UncheckedIOException(ex);
}
});
ServerResponse.Context context = Collections::emptyList;
ModelAndView mav = response.writeTo(this.mockRequest, this.mockResponse, context);
assertThat(mav).isNull();
String expected = ":line1\n:line2\n\n";
assertThat(this.mockResponse.getContentAsString()).isEqualTo(expected);
}
@Test // gh-34608
void sendHeartbeat() throws Exception {
ServerResponse response = ServerResponse.sse(sse -> {