Temporary attempt on addressing deploying custon message converters

spring-cloud-function-deployer/src/it/bootapp/pom.xml

@@ -27,6 +27,11 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-messaging</artifactId>
+			<scope>provided</scope>
+		</dependency>
 	</dependencies>
 
 	<build>

spring-cloud-function-deployer/src/it/bootapp/src/main/java/function/example/SimpleFunctionAppApplication.java

@@ -5,6 +5,10 @@ import java.util.function.Function;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.Bean;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.messaging.converter.MessageConverter;
+import org.springframework.messaging.support.MessageBuilder;
 
 @SpringBootApplication
 public class SimpleFunctionAppApplication {
@@ -30,6 +34,24 @@ public class SimpleFunctionAppApplication {
 		};
 	}
 
+	@Bean
+	public MessageConverter customConverter() {
+		return new MessageConverter() {
+
+			@Override
+			public Message<?> toMessage(Object payload, MessageHeaders headers) {
+				System.out.println("==== In Custom Message Converer: toMessage");
+				return null;
+			}
+
+			@Override
+			public Object fromMessage(Message<?> message, Class<?> targetClass) {
+				System.out.println("==== In Custom Message Converer: fromMessage");
+				return null;
+			}
+		};
+	}
+
 
 
 	public static class Person {

spring-cloud-function-deployer/src/main/java/org/springframework/cloud/function/deployer/FunctionArchiveDeployer.java

@@ -17,6 +17,7 @@
 package org.springframework.cloud.function.deployer;
 
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
 import java.net.URL;
@@ -26,9 +27,12 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicReference;
 
+import org.aopalliance.intercept.MethodInterceptor;
+import org.aopalliance.intercept.MethodInvocation;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.loader.JarLauncher;
 import org.springframework.boot.loader.LaunchedURLClassLoader;
@@ -41,6 +45,8 @@ import org.springframework.expression.Expression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.expression.spel.support.StandardTypeLocator;
+import org.springframework.messaging.converter.CompositeMessageConverter;
+import org.springframework.messaging.converter.MessageConverter;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.ReflectionUtils.MethodCallback;
@@ -77,6 +83,19 @@ class FunctionArchiveDeployer extends JarLauncher {
 			if (this.isBootApplicationWithMain()) {
 				this.launchFunctionArchive(args);
 
+				//=====
+				Map<String, MessageConverter> messageConverters = this.discoverMessageConverters(currentLoader);
+				if (!CollectionUtils.isEmpty(messageConverters)) {
+					Field mcField = functionRegistry.getClass().getDeclaredField("messageConverter");
+					mcField.setAccessible(true);
+					CompositeMessageConverter compositMessageConverter = (CompositeMessageConverter) mcField.get(functionRegistry);
+					List<MessageConverter> converters = compositMessageConverter.getConverters();
+					for (MessageConverter messageConverter : messageConverters.values()) {
+						converters.add(messageConverter);
+					}
+				}
+				//=====
+
 				Map<String, Object> functions = this.discoverBeanFunctions();
 				if (logger.isInfoEnabled() && !CollectionUtils.isEmpty(functions)) {
 					logger.info("Discovered functions in deployed application context: " + functions);
@@ -162,7 +181,8 @@ class FunctionArchiveDeployer extends JarLauncher {
 
 	private boolean shouldLoadViaDeployerLoader(String name) {
 		return name.startsWith("org.reactivestreams")
-				|| name.startsWith("reactor.");
+				|| name.startsWith("reactor.")
+				|| name.startsWith("org.springframework.messaging");
 	}
 
 	private String discoverFunctionClassName(FunctionDeployerProperties functionProperties) {
@@ -280,4 +300,38 @@ class FunctionArchiveDeployer extends JarLauncher {
 		}
 		return allFunctions;
 	}
+
+	@SuppressWarnings("unchecked")
+	private Map<String, MessageConverter> discoverMessageConverters(ClassLoader currentLoader) {
+		ClassLoader threadLoader = Thread.currentThread().getContextClassLoader();
+		Map<String, MessageConverter> exportedMessageConverters = new HashMap<>();
+		try {
+			if (evalContext.lookupVariable("context") != null) { // no start-class uber jars
+				Expression parsed = new SpelExpressionParser()
+						.parseExpression("#context.getBeansOfType(T(org.springframework.messaging.converter.MessageConverter))");
+				Thread.currentThread().setContextClassLoader(currentLoader);
+				Map<String, Object> targetMessageConverters = (Map<String, Object>) parsed.getValue(this.evalContext);
+
+				for (Entry<String, Object> messageConverterEntry : targetMessageConverters.entrySet()) {
+
+					ProxyFactory pf = new ProxyFactory(messageConverterEntry.getValue());
+					pf.setInterfaces(MessageConverter.class);
+					pf.addAdvice(new MethodInterceptor() {
+						@Override
+						public Object invoke(MethodInvocation invocation) throws Throwable {
+							System.out.println("=====> Invoking proxy");
+							return invocation.proceed();
+						}
+					});
+					MessageConverter converter = (MessageConverter) pf.getProxy();
+					exportedMessageConverters.put(messageConverterEntry.getKey(), converter);
+				}
+			}
+		}
+		finally {
+			Thread.currentThread().setContextClassLoader(threadLoader);
+		}
+
+		return exportedMessageConverters;
+	}
 }

spring-cloud-function-deployer/src/test/java/org/springframework/cloud/function/deployer/FunctionDeployerTests.java

@@ -174,6 +174,20 @@ public class FunctionDeployerTests {
 		assertThat(new String(result.getPayload(), StandardCharsets.UTF_8)).isEqualTo("\"BOB\"");
 	}
 
+//	@Test
+//	public void testWithMainAndStartClassAndSpringConfigurationCustomConverter() throws Exception {
+//		String[] args = new String[] {
+//				"--spring.cloud.function.location=target/it/bootapp/target/bootapp-1.0.0.RELEASE-exec.jar",
+//				"--spring.cloud.function.function-name=uppercase" };
+//		ApplicationContext context = SpringApplication.run(DeployerApplication.class, args);
+//		FunctionCatalog catalog = context.getBean(FunctionCatalog.class);
+//		Function<Message<byte[]>, Message<byte[]>> function = catalog.lookup("uppercase", "application/json");
+//
+//		Message<byte[]> result = function
+//				.apply(MessageBuilder.withPayload("\"bob\"".getBytes(StandardCharsets.UTF_8)).build());
+//		assertThat(new String(result.getPayload(), StandardCharsets.UTF_8)).isEqualTo("\"BOB\"");
+//	}
+
 	@Test
 	public void testWithLegacyProperties() throws Exception {
 		String[] args = new String[] {