Add FizzServerHttpResponseDecorator.java which can modify backend response to client

fizz-common/src/main/java/we/spring/http/server/reactive/ext/FizzServerHttpResponseDecorator.java

@@ -0,0 +1,69 @@
+/*
+ *  Copyright (C) 2020 the original author or authors.
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package we.spring.http.server.reactive.ext;
+
+import org.reactivestreams.Publisher;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.PooledDataBuffer;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
+import reactor.core.publisher.Mono;
+import we.util.NettyDataBufferUtils;
+
+/**
+ * @author hongqiaowei
+ */
+
+public abstract class FizzServerHttpResponseDecorator extends ServerHttpResponseDecorator {
+
+    public FizzServerHttpResponseDecorator(ServerHttpResponse delegate) {
+        super(delegate);
+    }
+
+    @Override
+    public Mono<Void> writeWith(Publisher<? extends DataBuffer> bodyPublisher) {
+
+        return
+                NettyDataBufferUtils.join(bodyPublisher).defaultIfEmpty(NettyDataBufferUtils.EMPTY_DATA_BUFFER)
+                                    .flatMap(
+                                            body -> {
+                                                DataBuffer b = null;
+                                                if (body != NettyDataBufferUtils.EMPTY_DATA_BUFFER) {
+                                                    if (body instanceof PooledDataBuffer) {
+                                                        try {
+                                                            b = NettyDataBufferUtils.from(body.asByteBuffer());
+                                                        } finally {
+                                                            NettyDataBufferUtils.release(body);
+                                                        }
+                                                    } else {
+                                                        b = body;
+                                                    }
+                                                }
+                                                Publisher<? extends DataBuffer> r = writeWith(b);
+                                                return super.writeWith(r);
+                                            }
+                                    );
+    }
+
+    /**
+     * You can getDelegate().getHeaders().set("h", "v") in the method and others for response.
+     * @param remoteResponseBody
+     * @return the real http response body to client, or Mono.empty() if response without body
+     */
+    public abstract Publisher<? extends DataBuffer> writeWith(DataBuffer remoteResponseBody);
+}