Fixed HttpHelloWorldServerHandler for handling HTTP 1.0/1.1 (netty#9124)

Motivation:

HttpHelloWorldServer example works incorrect for HTTP 1.1, the value of header connection is always set to close for each request.

Modification:

Correctly set header

Result:

Fixed HttpHelloWorldServerHandler for handling HTTP 1.0/1.1

example/src/main/java/io/netty/example/http/helloworld/HttpHelloWorldServerHandler.java

@@ -25,15 +25,14 @@
 import io.netty.handler.codec.http.HttpObject;
 import io.netty.handler.codec.http.HttpRequest;
 import io.netty.handler.codec.http.HttpUtil;
-import io.netty.handler.codec.http.HttpVersion;
 
 import static io.netty.handler.codec.http.HttpHeaderNames.CONNECTION;
 import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_LENGTH;
 import static io.netty.handler.codec.http.HttpHeaderNames.CONTENT_TYPE;
 import static io.netty.handler.codec.http.HttpHeaderValues.CLOSE;
 import static io.netty.handler.codec.http.HttpHeaderValues.KEEP_ALIVE;
+import static io.netty.handler.codec.http.HttpHeaderValues.TEXT_PLAIN;
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
-import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
 
 public class HttpHelloWorldServerHandler extends SimpleChannelInboundHandler<HttpObject> {
     private static final byte[] CONTENT = { 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd' };
@@ -49,12 +48,16 @@ public void channelRead0(ChannelHandlerContext ctx, HttpObject msg) {
             HttpRequest req = (HttpRequest) msg;
 
             boolean keepAlive = HttpUtil.isKeepAlive(req);
-            FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer(CONTENT));
-            response.headers().set(CONTENT_TYPE, "text/plain");
-            response.headers().setInt(CONTENT_LENGTH, response.content().readableBytes());
+            FullHttpResponse response = new DefaultFullHttpResponse(req.protocolVersion(), OK,
+                                                                    Unpooled.wrappedBuffer(CONTENT));
+            response.headers()
+                    .set(CONTENT_TYPE, TEXT_PLAIN)
+                    .setInt(CONTENT_LENGTH, response.content().readableBytes());
 
-            if (keepAlive && req.protocolVersion().equals(HttpVersion.HTTP_1_0)) {
-                response.headers().set(CONNECTION, KEEP_ALIVE);
+            if (keepAlive) {
+                if (!req.protocolVersion().isKeepAliveDefault()) {
+                    response.headers().set(CONNECTION, KEEP_ALIVE);
+                }
             } else {
                 // Tell the client we're going to close the connection.
                 response.headers().set(CONNECTION, CLOSE);