Avoided repeated creation of ReadOnlyHttpHeaders wrapper

See gh-24680

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

@@ -1769,7 +1769,9 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 
 
 	/**
-	 * Apply a read-only {@code HttpHeaders} wrapper around the given headers.
+	 * Apply a read-only {@code HttpHeaders} wrapper around the given headers
+	 * that also caches the parsed representations of the "Accept" and
+	 * "Content-Type" headers.
 	 */
 	public static HttpHeaders readOnlyHttpHeaders(MultiValueMap<String, String> headers) {
 		Assert.notNull(headers, "HttpHeaders must not be null");

spring-web/src/main/java/org/springframework/http/client/AbstractClientHttpRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -20,6 +20,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 import org.springframework.http.HttpHeaders;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -35,10 +36,22 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 
 	private boolean executed = false;
 
+	@Nullable
+	private HttpHeaders readOnlyHeaders;
+
 
 	@Override
 	public final HttpHeaders getHeaders() {
-		return (this.executed ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
+		if (this.readOnlyHeaders != null) {
+			return this.readOnlyHeaders;
+		}
+		else if (this.executed) {
+			this.readOnlyHeaders = HttpHeaders.readOnlyHttpHeaders(this.headers);
+			return this.readOnlyHeaders;
+		}
+		else {
+			return this.headers;
+		}
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/http/client/reactive/AbstractClientHttpRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -60,6 +60,9 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 
 	private final List<Supplier<? extends Publisher<Void>>> commitActions = new ArrayList<>(4);
 
+	@Nullable
+	private HttpHeaders readOnlyHeaders;
+
 
 	public AbstractClientHttpRequest() {
 		this(new HttpHeaders());
@@ -74,10 +77,16 @@ public abstract class AbstractClientHttpRequest implements ClientHttpRequest {
 
 	@Override
 	public HttpHeaders getHeaders() {
-		if (State.COMMITTED.equals(this.state.get())) {
-			return HttpHeaders.readOnlyHttpHeaders(this.headers);
+		if (this.readOnlyHeaders != null) {
+			return this.readOnlyHeaders;
+		}
+		else if (State.COMMITTED.equals(this.state.get())) {
+			this.readOnlyHeaders = HttpHeaders.readOnlyHttpHeaders(this.headers);
+			return this.readOnlyHeaders;
+		}
+		else {
+			return this.headers;
 		}
-		return this.headers;
 	}
 
 	@Override

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -47,6 +47,9 @@ public class ServletServerHttpResponse implements ServerHttpResponse {
 
 	private boolean bodyUsed = false;
 
+	@Nullable
+	private HttpHeaders readOnlyHeaders;
+
 
 	/**
 	 * Construct a new instance of the ServletServerHttpResponse based on the given {@link HttpServletResponse}.
@@ -74,7 +77,16 @@ public class ServletServerHttpResponse implements ServerHttpResponse {
 
 	@Override
 	public HttpHeaders getHeaders() {
-		return (this.headersWritten ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
+		if (this.readOnlyHeaders != null) {
+			return this.readOnlyHeaders;
+		}
+		else if (this.headersWritten) {
+			this.readOnlyHeaders = HttpHeaders.readOnlyHttpHeaders(this.headers);
+			return this.readOnlyHeaders;
+		}
+		else {
+			return this.headers;
+		}
 	}
 
 	@Override

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

@@ -75,6 +75,9 @@ public abstract class AbstractServerHttpResponse implements ServerHttpResponse {
 
 	private final List<Supplier<? extends Mono<Void>>> commitActions = new ArrayList<>(4);
 
+	@Nullable
+	private HttpHeaders readOnlyHeaders;
+
 
 	public AbstractServerHttpResponse(DataBufferFactory dataBufferFactory) {
 		this(dataBufferFactory, new HttpHeaders());
@@ -155,8 +158,16 @@ public abstract class AbstractServerHttpResponse implements ServerHttpResponse {
 
 	@Override
 	public HttpHeaders getHeaders() {
-		return (this.state.get() == State.COMMITTED ?
-				HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
+		if (this.readOnlyHeaders != null) {
+			return this.readOnlyHeaders;
+		}
+		else if (this.state.get() == State.COMMITTED) {
+			this.readOnlyHeaders = HttpHeaders.readOnlyHttpHeaders(this.headers);
+			return this.readOnlyHeaders;
+		}
+		else {
+			return this.headers;
+		}
 	}
 
 	@Override