HTTP header adapters print header values

Issue: SPR-17546

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -1640,7 +1640,26 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 
 	@Override
 	public String toString() {
-		return this.headers.toString();
+		return formatHeaders(this.headers);
+	}
+
+	/**
+	 * Helps to format HTTP header values, as HTTP header values themselves can
+	 * contain comma-separated values, can become confusing with regular
+	 * {@link Map} formatting that also uses commas between entries.
+	 * @param headers the headers to format
+	 * @return the headers to a String
+	 * @since 5.1.4
+	 */
+	public static String formatHeaders(MultiValueMap<String, String> headers) {
+		return headers.entrySet().stream()
+				.map(entry -> {
+					List<String> values = entry.getValue();
+					return entry.getKey() + ":" + (values.size() == 1 ?
+							"\"" + values.get(0) + "\"" :
+							values.stream().map(s -> "\"" + s + "\"").collect(Collectors.joining(", ")));
+				})
+				.collect(Collectors.joining(", ", "[", "]"));
 	}
 
 

spring-web/src/main/java/org/springframework/http/server/reactive/JettyHeadersAdapter.java

@@ -29,6 +29,7 @@ import java.util.stream.Collectors;
 import org.eclipse.jetty.http.HttpField;
 import org.eclipse.jetty.http.HttpFields;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.lang.Nullable;
 import org.springframework.util.MultiValueMap;
 
@@ -176,6 +177,12 @@ class JettyHeadersAdapter implements MultiValueMap<String, String> {
 	}
 
 
+	@Override
+	public String toString() {
+		return HttpHeaders.formatHeaders(this);
+	}
+
+
 	private class EntryIterator implements Iterator<Entry<String, List<String>>> {
 
 		private Enumeration<String> names = headers.getFieldNames();

spring-web/src/main/java/org/springframework/http/server/reactive/NettyHeadersAdapter.java

@@ -176,6 +176,12 @@ class NettyHeadersAdapter implements MultiValueMap<String, String> {
 	}
 
 
+	@Override
+	public String toString() {
+		return org.springframework.http.HttpHeaders.formatHeaders(this);
+	}
+
+
 	private class EntryIterator implements Iterator<Entry<String, List<String>>> {
 
 		private Iterator<String> names = headers.names().iterator();

spring-web/src/main/java/org/springframework/http/server/reactive/TomcatHeadersAdapter.java

@@ -31,6 +31,7 @@ import java.util.stream.Collectors;
 import org.apache.tomcat.util.buf.MessageBytes;
 import org.apache.tomcat.util.http.MimeHeaders;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.lang.Nullable;
 import org.springframework.util.MultiValueMap;
 
@@ -195,6 +196,12 @@ class TomcatHeadersAdapter implements MultiValueMap<String, String> {
 	}
 
 
+	@Override
+	public String toString() {
+		return HttpHeaders.formatHeaders(this);
+	}
+
+
 	private class EntryIterator implements Iterator<Entry<String, List<String>>> {
 
 		private Enumeration<String> names = headers.names();

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowHeadersAdapter.java

@@ -177,6 +177,12 @@ class UndertowHeadersAdapter implements MultiValueMap<String, String> {
 	}
 
 
+	@Override
+	public String toString() {
+		return org.springframework.http.HttpHeaders.formatHeaders(this);
+	}
+
+
 	private class EntryIterator implements Iterator<Entry<String, List<String>>> {
 
 		private Iterator<HttpString> names = headers.getHeaderNames().iterator();

spring-webflux/src/test/resources/log4j2-test.xml

@@ -2,7 +2,7 @@
 <Configuration status="WARN">
 	<Appenders>
 		<Console name="Console" target="SYSTEM_OUT">
-			<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
+			<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{1.} - %msg%n" />
 		</Console>
 	</Appenders>
 	<Loggers>