Add Content-Type header to AWScJson response and writer for servlet response

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ProxyHttpServletResponse.java

@@ -18,8 +18,10 @@ package org.springframework.cloud.function.serverless.web;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
+import java.io.Writer;
 import java.nio.charset.Charset;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
@@ -69,6 +71,8 @@ public class ProxyHttpServletResponse implements HttpServletResponse {
 
 	private int status = HttpServletResponse.SC_OK;
 
+	private ResponsePrintWriter writer;
+
 	@Nullable
 	private String errorMessage;
 
@@ -89,7 +93,11 @@ public class ProxyHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public PrintWriter getWriter() throws UnsupportedEncodingException {
-		throw new UnsupportedOperationException();
+		if (this.writer == null) {
+			Writer targetWriter = new OutputStreamWriter(this.content, getCharacterEncoding());
+			this.writer = new ResponsePrintWriter(targetWriter);
+		}
+		return this.writer;
 	}
 
 	public byte[] getContentAsByteArray() {
@@ -163,7 +171,7 @@ public class ProxyHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public boolean isCommitted() {
-		return false;
+		return this.writer == null ? false : this.writer.commited;
 	}
 
 	@Override
@@ -425,4 +433,47 @@ public class ProxyHttpServletResponse implements HttpServletResponse {
 		}
 	}
 
+	private class ResponsePrintWriter extends PrintWriter {
+
+		private boolean commited;
+
+		ResponsePrintWriter(Writer out) {
+			super(out, true);
+		}
+
+		@Override
+		public void write(char[] buf, int off, int len) {
+			super.write(buf, off, len);
+			super.flush();
+			this.commited = true;
+		}
+
+		@Override
+		public void write(String s, int off, int len) {
+			super.write(s, off, len);
+			super.flush();
+			this.commited = true;
+		}
+
+		@Override
+		public void write(int c) {
+			super.write(c);
+			super.flush();
+			this.commited = true;
+		}
+
+		@Override
+		public void flush() {
+			super.flush();
+			this.commited = true;
+		}
+
+		@Override
+		public void close() {
+			super.flush();
+			super.close();
+			this.commited = true;
+		}
+	}
+
 }

spring-cloud-function-adapters/spring-cloud-function-serverless-web/src/main/java/org/springframework/cloud/function/serverless/web/ProxyMvc.java

@@ -41,14 +41,13 @@ import jakarta.servlet.http.HttpServletResponse;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
-import org.springframework.context.annotation.AnnotatedBeanDefinitionReader;
+import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebApplicationContext;
 import org.springframework.http.HttpStatus;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.context.ConfigurableWebApplicationContext;
-import org.springframework.web.context.support.GenericWebApplicationContext;
 import org.springframework.web.servlet.DispatcherServlet;
 
 /**
@@ -85,11 +84,8 @@ public class ProxyMvc {
 	}
 
 	public static ProxyMvc INSTANCE(Class<?>... componentClasses) {
-		GenericWebApplicationContext applpicationContext = new GenericWebApplicationContext();
-		AnnotatedBeanDefinitionReader reader = new AnnotatedBeanDefinitionReader(applpicationContext);
-		if (!ObjectUtils.isEmpty(componentClasses)) {
-			reader.register(componentClasses);
-		}
+		AnnotationConfigServletWebApplicationContext applpicationContext = new AnnotationConfigServletWebApplicationContext();
+		applpicationContext.scan(componentClasses[0].getPackageName());
 		return INSTANCE(applpicationContext);
 	}
 
@@ -108,10 +104,17 @@ public class ProxyMvc {
 		reg.setLoadOnStartup(1);
 		this.servletContext = applicationContext.getServletContext();
 		try {
+
 			this.dispatcher.init(new ProxyServletConfig(this.servletContext));
+			try {
+				this.service(new ProxyHttpServletRequest(servletContext, "INFO", "/"), new ProxyHttpServletResponse());
+			}
+			catch (Exception e) {
+				//ignore as this is just a pre-warming attempt
+			}
 		}
 		catch (Exception e) {
-			throw new IllegalStateException(e);
+			throw new IllegalStateException("Faild to create Spring MVC DispatcherServlet proxy", e);
 		}
 	}
 
@@ -162,7 +165,7 @@ public class ProxyMvc {
 		 *
 		 * @param servlet the {@link Servlet} to invoke in this {@link FilterChain}
 		 * @param filters the {@link Filter}'s to invoke in this {@link FilterChain}
-		 * @since 3.2
+		 * @since 4.0.x
 		 */
 		ProxyFilterChain(DispatcherServlet servlet) {
 			List<Filter> filters = new ArrayList<>();