Avoided repeated creation of ReadOnlyHttpHeaders wrapper

See spring-projectsgh-24680

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

@@ -385,7 +385,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * An empty {@code HttpHeaders} instance (immutable).
 	 * @since 5.0
 	 */
-	public static final HttpHeaders EMPTY = new ReadOnlyHttpHeaders(new LinkedMultiValueMap<>());
+	public static final HttpHeaders EMPTY = new ReadOnlyHttpHeaders(new HttpHeaders(new LinkedMultiValueMap<>(0)));
 
 	/**
 	 * Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match".
@@ -1769,21 +1769,19 @@ public String toString() {
 
 
 	/**
-	 * Apply a read-only {@code HttpHeaders} wrapper around the given headers,
-	 * if necessary.
-	 * @param headers the headers to expose
-	 * @return a read-only variant of the headers, or the original headers as-is
+	 * 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(HttpHeaders headers) {
+	public static HttpHeaders readOnlyHttpHeaders(MultiValueMap<String, String> headers) {
 		Assert.notNull(headers, "HttpHeaders must not be null");
-		return (headers instanceof ReadOnlyHttpHeaders ? headers : new ReadOnlyHttpHeaders(headers.headers));
+		return (headers instanceof ReadOnlyHttpHeaders ?
+				(HttpHeaders) headers : new ReadOnlyHttpHeaders(headers));
 	}
 
 	/**
 	 * Remove any read-only wrapper that may have been previously applied around
-	 * the given headers via {@link #readOnlyHttpHeaders(HttpHeaders)}.
-	 * @param headers the headers to expose
-	 * @return a writable variant of the headers, or the original headers as-is
+	 * the given headers via {@link #readOnlyHttpHeaders(MultiValueMap)}.
 	 * @since 5.1.1
 	 */
 	public static HttpHeaders writableHttpHeaders(HttpHeaders headers) {

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.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 @@ private enum State {NEW, COMMITTING, COMMITTED}
 
 	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 AbstractClientHttpRequest(HttpHeaders headers) {
 
 	@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 void setStatusCode(HttpStatus status) {
 
 	@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 @@ private enum State {NEW, COMMITTING, COMMITTED}
 
 	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 Integer getStatusCodeValue() {
 
 	@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

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientResponse.java

@@ -234,29 +234,28 @@ HttpRequest request() {
 
 	private class DefaultHeaders implements Headers {
 
-		private HttpHeaders delegate() {
-			return response.getHeaders();
-		}
+		private final HttpHeaders httpHeaders =
+				HttpHeaders.readOnlyHttpHeaders(response.getHeaders());
 
 		@Override
 		public OptionalLong contentLength() {
-			return toOptionalLong(delegate().getContentLength());
+			return toOptionalLong(this.httpHeaders.getContentLength());
 		}
 
 		@Override
 		public Optional<MediaType> contentType() {
-			return Optional.ofNullable(delegate().getContentType());
+			return Optional.ofNullable(this.httpHeaders.getContentType());
 		}
 
 		@Override
 		public List<String> header(String headerName) {
-			List<String> headerValues = delegate().get(headerName);
+			List<String> headerValues = this.httpHeaders.get(headerName);
 			return (headerValues != null ? headerValues : Collections.emptyList());
 		}
 
 		@Override
 		public HttpHeaders asHttpHeaders() {
-			return HttpHeaders.readOnlyHttpHeaders(delegate());
+			return this.httpHeaders;
 		}
 
 		private OptionalLong toOptionalLong(long value) {

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java

@@ -106,24 +106,20 @@ public DefaultWebClientBuilder(DefaultWebClientBuilder other) {
 		this.defaultUriVariables = (other.defaultUriVariables != null ?
 				new LinkedHashMap<>(other.defaultUriVariables) : null);
 		this.uriBuilderFactory = other.uriBuilderFactory;
-
 		if (other.defaultHeaders != null) {
 			this.defaultHeaders = new HttpHeaders();
 			this.defaultHeaders.putAll(other.defaultHeaders);
 		}
 		else {
 			this.defaultHeaders = null;
 		}
-
 		this.defaultCookies = (other.defaultCookies != null ?
 				new LinkedMultiValueMap<>(other.defaultCookies) : null);
 		this.defaultRequest = other.defaultRequest;
-		this.filters = (other.filters != null ? new ArrayList<>(other.filters) : null);
-
+		this.filters = other.filters != null ? new ArrayList<>(other.filters) : null;
 		this.connector = other.connector;
 		this.strategies = other.strategies;
-		this.strategiesConfigurers = (other.strategiesConfigurers != null ?
-				new ArrayList<>(other.strategiesConfigurers) : null);
+		this.strategiesConfigurers = other.strategiesConfigurers != null ? new ArrayList<>(other.strategiesConfigurers) : null;
 		this.exchangeFunction = other.exchangeFunction;
 	}
 
@@ -232,8 +228,8 @@ public WebClient.Builder exchangeStrategies(ExchangeStrategies strategies) {
 		return this;
 	}
 
+	@SuppressWarnings("deprecation")
 	@Override
-	@Deprecated
 	public WebClient.Builder exchangeStrategies(Consumer<ExchangeStrategies.Builder> configurer) {
 		if (this.strategiesConfigurers == null) {
 			this.strategiesConfigurers = new ArrayList<>(4);
@@ -270,7 +266,7 @@ public WebClient build() {
 				.orElse(exchange) : exchange);
 		return new DefaultWebClient(filteredExchange, initUriBuilderFactory(),
 				this.defaultHeaders != null ? HttpHeaders.readOnlyHttpHeaders(this.defaultHeaders) : null,
-				this.defaultCookies != null ? CollectionUtils.unmodifiableMultiValueMap(this.defaultCookies) : null,
+				this.defaultCookies != null ? HttpHeaders.readOnlyHttpHeaders(this.defaultCookies) : null,
 				this.defaultRequest, new DefaultWebClientBuilder(this));
 	}
 
@@ -292,10 +288,12 @@ else if (httpComponentsClientPresent) {
 
 	private ExchangeStrategies initExchangeStrategies() {
 		if (CollectionUtils.isEmpty(this.strategiesConfigurers)) {
-			return (this.strategies != null ? this.strategies : ExchangeStrategies.withDefaults());
+			return this.strategies != null ? this.strategies : ExchangeStrategies.withDefaults();
 		}
+
 		ExchangeStrategies.Builder builder =
-				(this.strategies != null ? this.strategies.mutate() : ExchangeStrategies.builder());
+				this.strategies != null ? this.strategies.mutate() : ExchangeStrategies.builder();
+
 		this.strategiesConfigurers.forEach(configurer -> configurer.accept(builder));
 		return builder.build();
 	}
@@ -304,10 +302,14 @@ private UriBuilderFactory initUriBuilderFactory() {
 		if (this.uriBuilderFactory != null) {
 			return this.uriBuilderFactory;
 		}
-		DefaultUriBuilderFactory factory = (this.baseUrl != null ?
-				new DefaultUriBuilderFactory(this.baseUrl) : new DefaultUriBuilderFactory());
+		DefaultUriBuilderFactory factory = this.baseUrl != null ?
+				new DefaultUriBuilderFactory(this.baseUrl) : new DefaultUriBuilderFactory();
 		factory.setDefaultUriVariables(this.defaultUriVariables);
 		return factory;
 	}
 
+	private static <K, V> MultiValueMap<K, V> unmodifiableCopy(MultiValueMap<K, V> map) {
+		return CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(map));
+	}
+
 }

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerRequest.java

@@ -260,61 +260,60 @@ public String toString() {
 
 
 	private class DefaultHeaders implements Headers {
-
-		private HttpHeaders delegate() {
-			return request().getHeaders();
-		}
+
+		private final HttpHeaders httpHeaders =
+				HttpHeaders.readOnlyHttpHeaders(request().getHeaders());
 
 		@Override
 		public List<MediaType> accept() {
-			return delegate().getAccept();
+			return this.httpHeaders.getAccept();
 		}
 
 		@Override
 		public List<Charset> acceptCharset() {
-			return delegate().getAcceptCharset();
+			return this.httpHeaders.getAcceptCharset();
 		}
 
 		@Override
 		public List<Locale.LanguageRange> acceptLanguage() {
-			return delegate().getAcceptLanguage();
+			return this.httpHeaders.getAcceptLanguage();
 		}
 
 		@Override
 		public OptionalLong contentLength() {
-			long value = delegate().getContentLength();
+			long value = this.httpHeaders.getContentLength();
 			return (value != -1 ? OptionalLong.of(value) : OptionalLong.empty());
 		}
 
 		@Override
 		public Optional<MediaType> contentType() {
-			return Optional.ofNullable(delegate().getContentType());
+			return Optional.ofNullable(this.httpHeaders.getContentType());
 		}
 
 		@Override
 		public InetSocketAddress host() {
-			return delegate().getHost();
+			return this.httpHeaders.getHost();
 		}
 
 		@Override
 		public List<HttpRange> range() {
-			return delegate().getRange();
+			return this.httpHeaders.getRange();
 		}
 
 		@Override
 		public List<String> header(String headerName) {
-			List<String> headerValues = delegate().get(headerName);
+			List<String> headerValues = this.httpHeaders.get(headerName);
 			return (headerValues != null ? headerValues : Collections.emptyList());
 		}
 
 		@Override
 		public HttpHeaders asHttpHeaders() {
-			return HttpHeaders.readOnlyHttpHeaders(delegate());
+			return this.httpHeaders;
 		}
 
 		@Override
 		public String toString() {
-			return delegate().toString();
+			return this.httpHeaders.toString();
 		}
 	}