diff --git a/docs/pom.xml b/docs/pom.xml
index 86076b113..424cc4b99 100644
--- a/docs/pom.xml
+++ b/docs/pom.xml
@@ -8,7 +8,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<packaging>jar</packaging>
 	<name>Spring Cloud Function Docs</name>
diff --git a/pom.xml b/pom.xml
index 792f480e9..4b489d818 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,13 +6,13 @@
 
 	<artifactId>spring-cloud-function-parent</artifactId>
 	<name>Spring Cloud Function Parent</name>
-	<version>4.3.1-SNAPSHOT</version>
+	<version>5.0.0-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-build</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 		<relativePath/>
 	</parent>
 
diff --git a/spring-cloud-function-adapters/pom.xml b/spring-cloud-function-adapters/pom.xml
index 19b71d742..b5b698040 100644
--- a/spring-cloud-function-adapters/pom.xml
+++ b/spring-cloud-function-adapters/pom.xml
@@ -10,7 +10,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<name>spring-cloud-function-adapter-parent</name>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/pom.xml
index 21cc96285..eeddf4d8c 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/pom.xml
@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
index 0b55bc283..36df9beea 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
@@ -179,7 +179,7 @@ public final class CustomRuntimeEventLoop implements SmartLifecycle {
 			@Override
 			public int getRemainingTimeInMillis() {
 				long now = System.currentTimeMillis();
-				if (!headers.containsKey("Lambda-Runtime-Deadline-Ms")) {
+				if (!headers.containsHeader("Lambda-Runtime-Deadline-Ms")) {
 					return 0;
 				}
 				int delta = (int) (Long.parseLong(headers.getFirst("Lambda-Runtime-Deadline-Ms")) - now);
diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-azure-web/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-adapter-azure-web/pom.xml
index bbeeafd39..62f355193 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-azure-web/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-azure-web/pom.xml
@@ -9,7 +9,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-azure/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-adapter-azure/pom.xml
index 7fcf06dff..a0a080214 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-azure/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-azure/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/pom.xml
index b95fc3f17..487dfbdbd 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/pom.xml
@@ -11,7 +11,7 @@
 	<parent>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
 		<groupId>org.springframework.cloud</groupId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/org.springframework.cloud.function.aws-lambda.packaging.gradle.plugin/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/org.springframework.cloud.function.aws-lambda.packaging.gradle.plugin/pom.xml
index 9c708bac6..b5b155456 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/org.springframework.cloud.function.aws-lambda.packaging.gradle.plugin/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/org.springframework.cloud.function.aws-lambda.packaging.gradle.plugin/pom.xml
@@ -10,7 +10,7 @@
 	<parent>
 		<groupId>org.springframework.cloud.function.aws-lambda.packaging</groupId>
 		<artifactId>spring-cloud-function-aws-gradle-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<properties>
 		<main.basedir>${basedir}/../..</main.basedir>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/spring-cloud-function-aws-packaging-gradle-plugin/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/spring-cloud-function-aws-packaging-gradle-plugin/pom.xml
index 910d99d0e..36005c1aa 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/spring-cloud-function-aws-packaging-gradle-plugin/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-aws-gradle-parent/spring-cloud-function-aws-packaging-gradle-plugin/pom.xml
@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.cloud.function.aws-lambda.packaging</groupId>
 		<artifactId>spring-cloud-function-aws-gradle-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-grpc-cloudevent-ext/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-grpc-cloudevent-ext/pom.xml
index 43b3d283a..8da20a47b 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-grpc-cloudevent-ext/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-grpc-cloudevent-ext/pom.xml
@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>spring-cloud-function-grpc-cloudevent-ext</artifactId>
 	<name>spring-cloud-function-grpc-cloudevent-ext</name>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-grpc/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-grpc/pom.xml
index 014370827..161bf675b 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-grpc/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-grpc/pom.xml
@@ -10,7 +10,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<properties>
 		<grpc.version>1.55.1</grpc.version>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/pom.xml b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/pom.xml
index cb43c8b36..6d69207c4 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/pom.xml
+++ b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/pom.xml
@@ -10,7 +10,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-adapter-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
diff --git a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletRequest.java b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletRequest.java
index cdd9bd12e..637105145 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletRequest.java
+++ b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletRequest.java
@@ -279,7 +279,7 @@ public class ServerlessHttpServletRequest implements HttpServletRequest {
 	@Override
 	@Nullable
 	public String getContentType() {
-		return this.headers.containsKey(HttpHeaders.CONTENT_TYPE) ? this.headers.get(HttpHeaders.CONTENT_TYPE).get(0) : null;
+		return this.headers.containsHeader(HttpHeaders.CONTENT_TYPE) ? this.headers.get(HttpHeaders.CONTENT_TYPE).get(0) : null;
 	}
 
 	@Override
@@ -713,17 +713,17 @@ public class ServerlessHttpServletRequest implements HttpServletRequest {
 	@Override
 	@Nullable
 	public String getHeader(String name) {
-		return this.headers.containsKey(name) ? this.headers.get(name).get(0) : null;
+		return this.headers.containsHeader(name) ? this.headers.get(name).get(0) : null;
 	}
 
 	@Override
 	public Enumeration<String> getHeaders(String name) {
-		return Collections.enumeration(this.headers.containsKey(name) ? this.headers.get(name) : new LinkedList<>());
+		return Collections.enumeration(this.headers.containsHeader(name) ? this.headers.get(name) : new LinkedList<>());
 	}
 
 	@Override
 	public Enumeration<String> getHeaderNames() {
-		return Collections.enumeration(this.headers.keySet());
+		return Collections.enumeration(this.headers.headerNames());
 	}
 
 	public void setHeader(String name, @Nullable String value) {
@@ -735,7 +735,7 @@ public class ServerlessHttpServletRequest implements HttpServletRequest {
 	}
 
 	public void addHeaders(MultiValueMap<String, String> headers) {
-		this.headers.addAll(headers);
+		this.headers.addAll(new HttpHeaders(headers));
 	}
 
 	public void setHeaders(MultiValueMap<String, String> headers) {
diff --git a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletResponse.java b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletResponse.java
index 479d56911..2da0c8328 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletResponse.java
+++ b/spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ServerlessHttpServletResponse.java
@@ -217,7 +217,7 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public boolean containsHeader(String name) {
-		return this.headers.containsKey(name);
+		return this.headers.containsHeader(name);
 	}
 
 	/**
@@ -231,7 +231,7 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 	 */
 	@Override
 	public Collection<String> getHeaderNames() {
-		return this.headers.keySet();
+		return this.headers.headerNames();
 	}
 
 	/**
@@ -249,7 +249,7 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 	@Override
 	@Nullable
 	public String getHeader(String name) {
-		return this.headers.containsKey(name) ? this.headers.get(name).get(0) : null;
+		return this.headers.containsHeader(name) ? this.headers.get(name).get(0) : null;
 	}
 
 	/**
@@ -265,7 +265,7 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 	 */
 	@Override
 	public List<String> getHeaders(String name) {
-		if (!this.headers.containsKey(name)) {
+		if (!this.headers.containsHeader(name)) {
 			return Collections.emptyList();
 		}
 		return this.headers.get(name);
@@ -281,7 +281,7 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 	 */
 	@Nullable
 	public Object getHeaderValue(String name) {
-		return this.headers.containsKey(name) ? this.headers.get(name).get(0) : null;
+		return this.headers.containsHeader(name) ? this.headers.get(name).get(0) : null;
 	}
 
 	/**
@@ -329,6 +329,15 @@ public class ServerlessHttpServletResponse implements HttpServletResponse {
 		setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY);
 	}
 
+	@Override
+	public void sendRedirect(String location, int statusCode, boolean clearBuffer) throws IOException {
+		Assert.state(!isCommitted(), "Cannot send redirect - response is already committed");
+		Assert.notNull(location, "Redirect URL must not be null");
+		setHeader(HttpHeaders.LOCATION, location);
+		setStatus(statusCode);
+		//TODO: deal with clearBuffer
+	}
+
 	@Nullable
 	public String getRedirectedUrl() {
 		return getHeader(HttpHeaders.LOCATION);
diff --git a/spring-cloud-function-context/pom.xml b/spring-cloud-function-context/pom.xml
index ceb108494..ca143a74b 100644
--- a/spring-cloud-function-context/pom.xml
+++ b/spring-cloud-function-context/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-core/pom.xml b/spring-cloud-function-core/pom.xml
index 1cc5203cc..5534bda58 100644
--- a/spring-cloud-function-core/pom.xml
+++ b/spring-cloud-function-core/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<dependencies>
diff --git a/spring-cloud-function-dependencies/pom.xml b/spring-cloud-function-dependencies/pom.xml
index 1ee6c54f4..6b3f73b80 100644
--- a/spring-cloud-function-dependencies/pom.xml
+++ b/spring-cloud-function-dependencies/pom.xml
@@ -6,11 +6,11 @@
 	<parent>
 		<artifactId>spring-cloud-dependencies-parent</artifactId>
 		<groupId>org.springframework.cloud</groupId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 		<relativePath/>
 	</parent>
 	<artifactId>spring-cloud-function-dependencies</artifactId>
-	<version>4.3.1-SNAPSHOT</version>
+	<version>5.0.0-SNAPSHOT</version>
 	<packaging>pom</packaging>
 	<name>Spring Cloud Function Dependencies</name>
 	<description>Spring Cloud Function Dependencies</description>
diff --git a/spring-cloud-function-deployer/pom.xml b/spring-cloud-function-deployer/pom.xml
index 0e3a651b5..2a086f812 100644
--- a/spring-cloud-function-deployer/pom.xml
+++ b/spring-cloud-function-deployer/pom.xml
@@ -10,7 +10,7 @@
 		<parent>
 			<groupId>org.springframework.cloud</groupId>
 			<artifactId>spring-cloud-function-parent</artifactId>
-			<version>4.3.1-SNAPSHOT</version>
+			<version>5.0.0-SNAPSHOT</version>
 		</parent>
 
 	<properties>
diff --git a/spring-cloud-function-deployer/src/it/bootapp-multi/pom.xml b/spring-cloud-function-deployer/src/it/bootapp-multi/pom.xml
index 8ad6e52f3..b1db4c27c 100644
--- a/spring-cloud-function-deployer/src/it/bootapp-multi/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootapp-multi/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootapp-with-javax/pom.xml b/spring-cloud-function-deployer/src/it/bootapp-with-javax/pom.xml
index b4819cb59..516e730cf 100644
--- a/spring-cloud-function-deployer/src/it/bootapp-with-javax/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootapp-with-javax/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootapp-with-scf/pom.xml b/spring-cloud-function-deployer/src/it/bootapp-with-scf/pom.xml
index b5f552b68..fc8756fd5 100644
--- a/spring-cloud-function-deployer/src/it/bootapp-with-scf/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootapp-with-scf/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootapp/pom.xml b/spring-cloud-function-deployer/src/it/bootapp/pom.xml
index a98c8563a..259cbc0e7 100644
--- a/spring-cloud-function-deployer/src/it/bootapp/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootapp/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootjar-multi/pom.xml b/spring-cloud-function-deployer/src/it/bootjar-multi/pom.xml
index c18506ba7..6a00111fa 100644
--- a/spring-cloud-function-deployer/src/it/bootjar-multi/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootjar-multi/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootjar/pom.xml b/spring-cloud-function-deployer/src/it/bootjar/pom.xml
index 73c6ce8bb..c41c8521e 100644
--- a/spring-cloud-function-deployer/src/it/bootjar/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootjar/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-deployer/src/it/bootjarnostart/pom.xml b/spring-cloud-function-deployer/src/it/bootjarnostart/pom.xml
index 8323db076..d6fa20553 100644
--- a/spring-cloud-function-deployer/src/it/bootjarnostart/pom.xml
+++ b/spring-cloud-function-deployer/src/it/bootjarnostart/pom.xml
@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-integration/pom.xml b/spring-cloud-function-integration/pom.xml
index 554c52c13..45a83da9c 100644
--- a/spring-cloud-function-integration/pom.xml
+++ b/spring-cloud-function-integration/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<artifactId>spring-cloud-function-parent</artifactId>
 		<groupId>org.springframework.cloud</groupId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 
diff --git a/spring-cloud-function-kotlin/pom.xml b/spring-cloud-function-kotlin/pom.xml
index 29e477d81..d3bc48727 100644
--- a/spring-cloud-function-kotlin/pom.xml
+++ b/spring-cloud-function-kotlin/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<dependencies>
diff --git a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinLambdasConfiguration.kt b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinLambdasConfiguration.kt
index a324131fc..c248f135b 100644
--- a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinLambdasConfiguration.kt
+++ b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinLambdasConfiguration.kt
@@ -34,7 +34,7 @@ open class KotlinLambdasConfiguration {
 	open fun uppercase(): Function<String, String> = KotlinComponentFunction()
 	@Bean
 	open fun kotlinFunction(): (String) -> String {
-		return { it.toUpperCase() }
+		return { it.uppercase() }
 	}
 
 	@Bean
diff --git a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinSuspendFlowLambdasConfiguration.kt b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinSuspendFlowLambdasConfiguration.kt
index bfa7e3102..0131698db 100644
--- a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinSuspendFlowLambdasConfiguration.kt
+++ b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/KotlinSuspendFlowLambdasConfiguration.kt
@@ -36,7 +36,7 @@ open class KotlinSuspendFlowLambdasConfiguration {
 
 	@Bean
 	open fun kotlinFunction(): suspend (Flow<String>) -> Flow<String> =  { flow ->
-		flow.map { value -> value.toUpperCase() }
+		flow.map { value -> value.uppercase() }
 	}
 	
 	@Bean
diff --git a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageSuspendTests.kt b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageSuspendTests.kt
index 85ad7f68f..9dd2d2349 100644
--- a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageSuspendTests.kt
+++ b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageSuspendTests.kt
@@ -56,7 +56,7 @@ open class HeadersToMessageSuspendTests {
 			)
 
 		Assertions.assertThat(postForEntity.body).isEqualTo("[{\"name\":\"Bob\",\"age\":25}]")
-		Assertions.assertThat(postForEntity.headers.containsKey("x-content-type")).isTrue
+		Assertions.assertThat(postForEntity.headers.headerNames()).contains("x-content-type")
 		Assertions.assertThat(postForEntity.headers["x-content-type"]!![0])
 			.isEqualTo("application/xml")
 		Assertions.assertThat(postForEntity.headers["foo"]!![0]).isEqualTo("bar")
@@ -67,7 +67,7 @@ open class HeadersToMessageSuspendTests {
 			"HELLO", String::class.java
 		)
 		Assertions.assertThat(postForEntity.body).isEqualTo("[\"HELLO\"]")
-		Assertions.assertThat(postForEntity.headers.containsKey("x-content-type")).isTrue
+		Assertions.assertThat(postForEntity.headers.headerNames()).contains("x-content-type")
 		Assertions.assertThat(postForEntity.headers["x-content-type"]!![0])
 			.isEqualTo("application/xml")
 		Assertions.assertThat(postForEntity.headers["foo"]!![0]).isEqualTo("bar")
diff --git a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageTests.kt b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageTests.kt
index 02f1c170d..68214d4f7 100644
--- a/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageTests.kt
+++ b/spring-cloud-function-kotlin/src/test/kotlin/org/springframework/cloud/function/kotlin/web/HeadersToMessageTests.kt
@@ -55,7 +55,7 @@ open class HeadersToMessageTests {
 					.body("{\"name\":\"Bob\",\"age\":25}"), String::class.java
 			)
 		Assertions.assertThat(postForEntity.body).isEqualTo("{\"name\":\"Bob\",\"age\":25}")
-		Assertions.assertThat(postForEntity.headers.containsKey("x-content-type")).isTrue
+		Assertions.assertThat(postForEntity.headers.headerNames()).contains("x-content-type")
 		Assertions.assertThat(postForEntity.headers["x-content-type"]!![0])
 			.isEqualTo("application/xml")
 		Assertions.assertThat(postForEntity.headers["foo"]!![0]).isEqualTo("bar")
@@ -66,7 +66,7 @@ open class HeadersToMessageTests {
 			"{\"name\":\"Bob\",\"age\":25}", String::class.java
 		)
 		Assertions.assertThat(postForEntity.body).isEqualTo("{\"name\":\"Bob\",\"age\":25}")
-		Assertions.assertThat(postForEntity.headers.containsKey("x-content-type")).isTrue
+		Assertions.assertThat(postForEntity.headers.headerNames().contains("x-content-type"))
 		Assertions.assertThat(postForEntity.headers["x-content-type"]!![0])
 			.isEqualTo("application/xml")
 		Assertions.assertThat(postForEntity.headers["foo"]!![0]).isEqualTo("bar")
@@ -76,9 +76,9 @@ open class HeadersToMessageTests {
 	@org.springframework.boot.test.context.TestConfiguration
 	open class TestConfiguration {
 		@Bean("string")
-		open fun functiono(): (message: Message<String?>) -> Message<String?> = { request: Message<String?> ->
-			val message =
-				MessageBuilder.withPayload(request.payload)
+		open fun functiono(): (message: Message<String>) -> Message<String> = { request: Message<String> ->
+			val message: Message<String> =
+				MessageBuilder.withPayload(request.payload as String)
 					.setHeader("X-Content-Type", "application/xml")
 					.setHeader("foo", "bar").build()
 			message
diff --git a/spring-cloud-function-rsocket/pom.xml b/spring-cloud-function-rsocket/pom.xml
index 20f89375f..7c4d0e547 100644
--- a/spring-cloud-function-rsocket/pom.xml
+++ b/spring-cloud-function-rsocket/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<properties>
diff --git a/spring-cloud-function-samples/function-functional-sample-aws/pom.xml b/spring-cloud-function-samples/function-functional-sample-aws/pom.xml
index c3453fbf8..ed06a2a76 100644
--- a/spring-cloud-function-samples/function-functional-sample-aws/pom.xml
+++ b/spring-cloud-function-samples/function-functional-sample-aws/pom.xml
@@ -24,7 +24,7 @@
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 		<aws-lambda-events.version>3.14.0</aws-lambda-events.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-aws-custom-bean/pom.xml b/spring-cloud-function-samples/function-sample-aws-custom-bean/pom.xml
index d39a1c09c..462932474 100644
--- a/spring-cloud-function-samples/function-sample-aws-custom-bean/pom.xml
+++ b/spring-cloud-function-samples/function-sample-aws-custom-bean/pom.xml
@@ -16,7 +16,7 @@
 
 	<properties>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-aws-custom/pom.xml b/spring-cloud-function-samples/function-sample-aws-custom/pom.xml
index 27250dbab..ddf955f53 100644
--- a/spring-cloud-function-samples/function-sample-aws-custom/pom.xml
+++ b/spring-cloud-function-samples/function-sample-aws-custom/pom.xml
@@ -16,7 +16,7 @@
 
 	<properties>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-aws-routing/pom.xml b/spring-cloud-function-samples/function-sample-aws-routing/pom.xml
index 77f680f78..c54deed11 100644
--- a/spring-cloud-function-samples/function-sample-aws-routing/pom.xml
+++ b/spring-cloud-function-samples/function-sample-aws-routing/pom.xml
@@ -24,7 +24,7 @@
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 		<aws-lambda-events.version>3.14.0</aws-lambda-events.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-aws/pom.xml b/spring-cloud-function-samples/function-sample-aws/pom.xml
index a754ad037..aa2cb0ca1 100644
--- a/spring-cloud-function-samples/function-sample-aws/pom.xml
+++ b/spring-cloud-function-samples/function-sample-aws/pom.xml
@@ -24,7 +24,7 @@
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 		<aws-lambda-events.version>3.14.0</aws-lambda-events.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-cloudevent-rsocket/pom.xml b/spring-cloud-function-samples/function-sample-cloudevent-rsocket/pom.xml
index 65e854ed6..3a5c0395e 100644
--- a/spring-cloud-function-samples/function-sample-cloudevent-rsocket/pom.xml
+++ b/spring-cloud-function-samples/function-sample-cloudevent-rsocket/pom.xml
@@ -16,7 +16,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/function-sample-cloudevent-sdk/pom.xml b/spring-cloud-function-samples/function-sample-cloudevent-sdk/pom.xml
index b17585d26..5917fb153 100644
--- a/spring-cloud-function-samples/function-sample-cloudevent-sdk/pom.xml
+++ b/spring-cloud-function-samples/function-sample-cloudevent-sdk/pom.xml
@@ -16,7 +16,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/function-sample-cloudevent-stream/pom.xml b/spring-cloud-function-samples/function-sample-cloudevent-stream/pom.xml
index 4d2e26994..ff831c774 100644
--- a/spring-cloud-function-samples/function-sample-cloudevent-stream/pom.xml
+++ b/spring-cloud-function-samples/function-sample-cloudevent-stream/pom.xml
@@ -16,7 +16,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/function-sample-cloudevent/pom.xml b/spring-cloud-function-samples/function-sample-cloudevent/pom.xml
index 2311ff15b..8c7bfb36c 100644
--- a/spring-cloud-function-samples/function-sample-cloudevent/pom.xml
+++ b/spring-cloud-function-samples/function-sample-cloudevent/pom.xml
@@ -16,7 +16,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/function-sample-functional-aws-routing/pom.xml b/spring-cloud-function-samples/function-sample-functional-aws-routing/pom.xml
index 80e04401c..2ecf38ac6 100644
--- a/spring-cloud-function-samples/function-sample-functional-aws-routing/pom.xml
+++ b/spring-cloud-function-samples/function-sample-functional-aws-routing/pom.xml
@@ -24,7 +24,7 @@
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 		<aws-lambda-events.version>3.14.0</aws-lambda-events.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-gcp-http/pom.xml b/spring-cloud-function-samples/function-sample-gcp-http/pom.xml
index 463cb27f0..e73502d93 100644
--- a/spring-cloud-function-samples/function-sample-gcp-http/pom.xml
+++ b/spring-cloud-function-samples/function-sample-gcp-http/pom.xml
@@ -20,7 +20,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-grpc-cloudevent/pom.xml b/spring-cloud-function-samples/function-sample-grpc-cloudevent/pom.xml
index c81a3c32f..ce30d8709 100644
--- a/spring-cloud-function-samples/function-sample-grpc-cloudevent/pom.xml
+++ b/spring-cloud-function-samples/function-sample-grpc-cloudevent/pom.xml
@@ -16,7 +16,7 @@
 	<name>function-sample-grpc-cloudevent</name>
 	<description>Demo project for Spring Boot</description>
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<grpc.version>1.55.1</grpc.version>
 	</properties>
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-pof/pom.xml b/spring-cloud-function-samples/function-sample-pof/pom.xml
index ff9b98525..20323fa3a 100644
--- a/spring-cloud-function-samples/function-sample-pof/pom.xml
+++ b/spring-cloud-function-samples/function-sample-pof/pom.xml
@@ -21,7 +21,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<reactor.version>3.1.2.RELEASE</reactor.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-pojo/pom.xml b/spring-cloud-function-samples/function-sample-pojo/pom.xml
index e0c4e19aa..16d8a4fcf 100644
--- a/spring-cloud-function-samples/function-sample-pojo/pom.xml
+++ b/spring-cloud-function-samples/function-sample-pojo/pom.xml
@@ -19,7 +19,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/function-sample-spring-integration/pom.xml b/spring-cloud-function-samples/function-sample-spring-integration/pom.xml
index 59d680728..a5895a42a 100644
--- a/spring-cloud-function-samples/function-sample-spring-integration/pom.xml
+++ b/spring-cloud-function-samples/function-sample-spring-integration/pom.xml
@@ -20,7 +20,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 		<java.version>17</java.version>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample-supplier-exporter/pom.xml b/spring-cloud-function-samples/function-sample-supplier-exporter/pom.xml
index f9c1133b2..6fa68ec68 100644
--- a/spring-cloud-function-samples/function-sample-supplier-exporter/pom.xml
+++ b/spring-cloud-function-samples/function-sample-supplier-exporter/pom.xml
@@ -19,7 +19,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 	</properties>
 
 	<dependencies>
diff --git a/spring-cloud-function-samples/function-sample/pom.xml b/spring-cloud-function-samples/function-sample/pom.xml
index da953ab28..3546698b4 100644
--- a/spring-cloud-function-samples/function-sample/pom.xml
+++ b/spring-cloud-function-samples/function-sample/pom.xml
@@ -19,7 +19,7 @@
 	</parent>
 
 	<properties>
-		<spring-cloud-function.version>4.3.1-SNAPSHOT</spring-cloud-function.version>
+		<spring-cloud-function.version>5.0.0-SNAPSHOT</spring-cloud-function.version>
 		<wrapper.version>1.0.31.RELEASE</wrapper.version>
 	</properties>
 
diff --git a/spring-cloud-function-samples/pom.xml b/spring-cloud-function-samples/pom.xml
index 6c63d1b81..60495db4c 100644
--- a/spring-cloud-function-samples/pom.xml
+++ b/spring-cloud-function-samples/pom.xml
@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<modules>
diff --git a/spring-cloud-function-web/pom.xml b/spring-cloud-function-web/pom.xml
index 1c196001e..27e3add56 100644
--- a/spring-cloud-function-web/pom.xml
+++ b/spring-cloud-function-web/pom.xml
@@ -12,7 +12,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 
 	<dependencies>
diff --git a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/mvc/FunctionController.java b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/mvc/FunctionController.java
index f0e5ee673..222cd9401 100644
--- a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/mvc/FunctionController.java
+++ b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/mvc/FunctionController.java
@@ -81,7 +81,7 @@ public class FunctionController {
 															.getRequest()).getMultiFileMap();
 				if (!CollectionUtils.isEmpty(multiFileMap)) {
 					List<Message<MultipartFile>> files = multiFileMap.values().stream().flatMap(v -> v.stream())
-							.map(file -> MessageBuilder.withPayload(file).copyHeaders(wrapper.getHeaders()).build())
+							.map(file -> MessageBuilder.withPayload(file).copyHeaders(wrapper.getHeaders().asMultiValueMap()).build())
 							.collect(Collectors.toList());
 					FunctionInvocationWrapper function = wrapper.getFunction();
 
@@ -199,7 +199,7 @@ public class FunctionController {
 			wrapper.getHeaders().addAll(key, Arrays.asList(request.getHeaderValues(key)));
 		}
 
-		HttpHeaders headers = HttpHeaders.writableHttpHeaders(wrapper.getHeaders());
+		HttpHeaders headers = HttpHeaders.copyOf(wrapper.getHeaders());
 		headers.set("uri", ((ServletWebRequest) request).getRequest().getRequestURI());
 
 		String argument = (String) request.getAttribute(WebRequestConstants.ARGUMENT,
diff --git a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/HttpSupplier.java b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/HttpSupplier.java
index 84574187e..2e383e5a2 100644
--- a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/HttpSupplier.java
+++ b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/HttpSupplier.java
@@ -65,8 +65,8 @@ public class HttpSupplier implements Supplier<Flux<?>> {
 	}
 
 	private Flux<?> get(WebClient client) {
-		Flux<?> result = client.get().uri(this.props.getSource().getUrl()).exchange()
-				.flatMap(this::transform).repeat();
+		Flux<?> result = client.get().uri(this.props.getSource().getUrl()).exchangeToMono(this::transform)
+				.repeat();
 		if (this.props.isDebug()) {
 			result = result.log();
 		}
diff --git a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/SupplierExporter.java b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/SupplierExporter.java
index 8a24e8455..18cb3b1fd 100644
--- a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/SupplierExporter.java
+++ b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/source/SupplierExporter.java
@@ -192,11 +192,11 @@ public class SupplierExporter implements SmartLifecycle {
 		}
 		Mono<ClientResponse> result = this.client.post().uri(uri)
 				.headers(headers -> headers(headers, destination, value)).bodyValue(body)
-				.exchange()
-				.doOnNext(response -> {
+				.exchangeToMono(response -> {
 					if (this.debug) {
 						logger.debug("Response STATUS: " + response.statusCode());
 					}
+					return Mono.just(response);
 				});
 		if (this.debug) {
 			result = result.log();
diff --git a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/util/HeaderUtils.java b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/util/HeaderUtils.java
index d4382fe6f..e5d728daa 100644
--- a/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/util/HeaderUtils.java
+++ b/spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/util/HeaderUtils.java
@@ -62,7 +62,7 @@ public final class HeaderUtils {
 		for (String name : headers.keySet()) {
 			Object value = headers.get(name);
 			name = name.toLowerCase(Locale.ROOT);
-			if (!IGNORED.containsKey(name) && !ignoredHeders.contains(name)) {
+			if (!IGNORED.containsHeader(name) && !ignoredHeders.contains(name)) {
 				Collection<?> values = multi(value);
 				for (Object object : values) {
 					result.set(name, object.toString());
@@ -80,10 +80,10 @@ public final class HeaderUtils {
 
 	public static HttpHeaders sanitize(HttpHeaders request, List<String> ignoredHeders, List<String> requestOnlyHeaders) {
 		HttpHeaders result = new HttpHeaders();
-		for (String name : request.keySet()) {
+		for (String name : request.headerNames()) {
 			List<String> value = request.get(name);
 			name = name.toLowerCase(Locale.ROOT);
-			if (!IGNORED.containsKey(name) && !REQUEST_ONLY.containsKey(name) && !ignoredHeders.contains(name) && !requestOnlyHeaders.contains(name)) {
+			if (!IGNORED.containsHeader(name) && !REQUEST_ONLY.containsHeader(name) && !ignoredHeders.contains(name) && !requestOnlyHeaders.contains(name)) {
 				result.put(name, value);
 			}
 		}
@@ -97,7 +97,7 @@ public final class HeaderUtils {
 
 	public static MessageHeaders fromHttp(HttpHeaders headers) {
 		Map<String, Object> map = new LinkedHashMap<>();
-		for (String name : headers.keySet()) {
+		for (String name : headers.headerNames()) {
 			Collection<?> values = multi(headers.get(name));
 			name = name.toLowerCase(Locale.ROOT);
 			Object value = values == null ? null
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HeadersToMessageTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HeadersToMessageTests.java
index 06ec2bdb1..3cb40b0df 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HeadersToMessageTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HeadersToMessageTests.java
@@ -60,7 +60,7 @@ public class HeadersToMessageTests {
 						.contentType(MediaType.APPLICATION_JSON)
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
-		assertThat(postForEntity.getHeaders().containsKey("x-content-type")).isTrue();
+		assertThat(postForEntity.getHeaders().containsHeader("x-content-type")).isTrue();
 		assertThat(postForEntity.getHeaders().get("x-content-type").get(0))
 				.isEqualTo("application/xml");
 		assertThat(postForEntity.getHeaders().get("foo").get(0)).isEqualTo("bar");
@@ -69,7 +69,7 @@ public class HeadersToMessageTests {
 		postForEntity = this.rest.postForEntity(new URI("/functions/string"),
 				"{\"name\":\"Bob\",\"age\":25}", String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
-		assertThat(postForEntity.getHeaders().containsKey("x-content-type")).isTrue();
+		assertThat(postForEntity.getHeaders().containsHeader("x-content-type")).isTrue();
 		assertThat(postForEntity.getHeaders().get("x-content-type").get(0))
 				.isEqualTo("application/xml");
 		assertThat(postForEntity.getHeaders().get("foo").get(0)).isEqualTo("bar");
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HttpPostIntegrationTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HttpPostIntegrationTests.java
index eb4d61ab8..6fdc46656 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HttpPostIntegrationTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HttpPostIntegrationTests.java
@@ -170,7 +170,7 @@ public class HttpPostIntegrationTests {
 				.post(new URI("/messages")).contentType(MediaType.APPLICATION_JSON)
 				.header("x-foo", "bar").body("[\"foo\",\"bar\"]"), String.class);
 		assertThat(result.getHeaders().getFirst("x-foo")).isEqualTo("bar");
-		assertThat(result.getHeaders()).doesNotContainKey("id");
+		assertThat(result.getHeaders().headerNames()).doesNotContain("id");
 		assertThat(result.getBody()).isEqualTo("[\"(FOO)\",\"(BAR)\"]");
 	}
 
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializerTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializerTests.java
index 66189a9de..110501f0b 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializerTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/function/FunctionEndpointInitializerTests.java
@@ -72,7 +72,7 @@ public class FunctionEndpointInitializerTests {
 		headers.set("Accept", "application/json");
 		HttpEntity entity = new HttpEntity(headers);
 
-		String urlTemplate = UriComponentsBuilder.fromHttpUrl("http://localhost:" + port + "/nullPayload")
+		String urlTemplate = UriComponentsBuilder.fromUriString("http://localhost:" + port + "/nullPayload")
 				.queryParam("fname", "Jim").queryParam("lname", "Lahey").encode().toUriString();
 
 		ResponseEntity<String> response = testRestTemplate.exchange(urlTemplate, HttpMethod.GET, entity, String.class);
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HeadersToMessageTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HeadersToMessageTests.java
index 14c264aee..0527e2928 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HeadersToMessageTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HeadersToMessageTests.java
@@ -60,7 +60,7 @@ public class HeadersToMessageTests {
 						.contentType(MediaType.APPLICATION_JSON)
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
-		assertThat(postForEntity.getHeaders().containsKey("x-content-type")).isTrue();
+		assertThat(postForEntity.getHeaders().headerNames()).contains("x-content-type");
 		assertThat(postForEntity.getHeaders().get("x-content-type").get(0))
 				.isEqualTo("application/xml");
 		assertThat(postForEntity.getHeaders().get("foo").get(0)).isEqualTo("bar");
@@ -75,7 +75,7 @@ public class HeadersToMessageTests {
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody())
 				.isEqualTo("{\"name\":\"Bob\",\"age\":25,\"foo\":\"bar\"}");
-		assertThat(postForEntity.getHeaders().containsKey("x-context-type")).isTrue();
+		assertThat(postForEntity.getHeaders().headerNames()).contains("x-context-type");
 		assertThat(postForEntity.getHeaders().get("x-context-type").get(0))
 				.isEqualTo("rubbish");
 	}
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HttpPostIntegrationTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HttpPostIntegrationTests.java
index b3d9b2aa4..83b0f790c 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HttpPostIntegrationTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HttpPostIntegrationTests.java
@@ -145,7 +145,7 @@ public class HttpPostIntegrationTests {
 				.accept(MediaType.valueOf("application/stream+json"))
 				.header("x-foo", "bar").body("[\"foo\",\"bar\"]"), String.class);
 		assertThat(result.getHeaders().getFirst("x-foo")).isEqualTo("bar");
-		assertThat(result.getHeaders()).doesNotContainKey("id");
+		assertThat(result.getHeaders().headerNames()).doesNotContain("id");
 		assertThat(result.getBody()).isEqualTo("[\"(FOO)\",\"(BAR)\"]");
 	}
 
@@ -157,7 +157,7 @@ public class HttpPostIntegrationTests {
 				.accept(MediaType.valueOf("application/stream+json"))
 				.body("[\"foo\",\"bar\"]"), String.class);
 		assertThat(result.getHeaders().getFirst("foo")).isEqualTo("bar");
-		assertThat(result.getHeaders()).doesNotContainKey("id");
+		assertThat(result.getHeaders().headerNames()).doesNotContain("id");
 		assertThat(result.getBody()).isEqualTo("[\"(FOO)\",\"(BAR)\"]");
 	}
 
diff --git a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/RoutingFunctionTests.java b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/RoutingFunctionTests.java
index b107d96bf..ce8dcfdab 100644
--- a/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/RoutingFunctionTests.java
+++ b/spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/RoutingFunctionTests.java
@@ -72,19 +72,18 @@ public class RoutingFunctionTests {
 	public void testFunctionMessage() throws Exception {
 
 		HttpEntity<String> postForEntity = this.rest
-				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
-						.contentType(MediaType.APPLICATION_JSON)
-						.header("spring.cloud.function.definition", "employee")
-						.header("abc", "abc")
-						.header("xyz", "xyz")
-						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
+			.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
+				.contentType(MediaType.APPLICATION_JSON)
+				.header("spring.cloud.function.definition", "employee")
+				.header("abc", "abc")
+				.header("xyz", "xyz")
+				.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
-		assertThat(postForEntity.getHeaders().containsKey("x-content-type")).isTrue();
+		assertThat(postForEntity.getHeaders().headerNames()).contains("x-content-type");
 		assertThat(postForEntity.getHeaders().get("x-content-type").get(0))
-				.isEqualTo("application/xml");
-		assertThat(postForEntity.getHeaders().containsKey("spring.cloud.function.definition")).isTrue();
-		assertThat(postForEntity.getHeaders().containsKey("abc")).isFalse();
-		assertThat(postForEntity.getHeaders().containsKey("xyz")).isFalse();
+			.isEqualTo("application/xml");
+		assertThat(postForEntity.getHeaders().headerNames()).contains("spring.cloud.function.definition")
+			.doesNotContain("abc", "xyz");
 		assertThat(postForEntity.getHeaders().get("foo").get(0)).isEqualTo("bar");
 	}
 
diff --git a/spring-cloud-starter-function-web/pom.xml b/spring-cloud-starter-function-web/pom.xml
index 22137ce48..5a33ae6f4 100644
--- a/spring-cloud-starter-function-web/pom.xml
+++ b/spring-cloud-starter-function-web/pom.xml
@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 		<relativePath>..</relativePath>
 	</parent>
 	<artifactId>spring-cloud-starter-function-web</artifactId>
diff --git a/spring-cloud-starter-function-webflux/pom.xml b/spring-cloud-starter-function-webflux/pom.xml
index 46d1bb40f..90c99fd92 100644
--- a/spring-cloud-starter-function-webflux/pom.xml
+++ b/spring-cloud-starter-function-webflux/pom.xml
@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>org.springframework.cloud</groupId>
 		<artifactId>spring-cloud-function-parent</artifactId>
-		<version>4.3.1-SNAPSHOT</version>
+		<version>5.0.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>spring-cloud-starter-function-webflux</artifactId>
 	<name>spring-cloud-starter-function-webflux</name>