* Added code for BAEL-1972 (#4632)

spring-5-reactive/src/main/java/com/baeldung/reactive/responseheaders/controllers/ResponseHeaderController.java

@@ -0,0 +1,35 @@
+package com.baeldung.reactive.responseheaders.controllers;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import reactor.core.publisher.Mono;
+
+@RestController
+@RequestMapping("/response-header")
+public class ResponseHeaderController {
+
+    @GetMapping("/response-entity")
+    public Mono<ResponseEntity<String>> usingResponseEntityBuilder() {
+        String responseHeaderKey = "Baeldung-Example-Header";
+        String responseHeaderValue = "Value-ResponseEntityBuilder";
+        String responseBody = "Response with header using ResponseEntity (builder)";
+
+        return Mono.just(ResponseEntity.ok()
+            .header(responseHeaderKey, responseHeaderValue)
+            .body(responseBody));
+    }
+    
+    @GetMapping("/server-http-response")
+    public Mono<String> usingServerHttpResponse(ServerHttpResponse response) {
+        String responseHeaderKey = "Baeldung-Example-Header";
+        String responseHeaderValue = "Value-ServerHttpResponse";
+        String responseBody = "Response with header using ServerHttpResponse";
+        
+        response.getHeaders().add(responseHeaderKey, responseHeaderValue);
+        return Mono.just(responseBody);
+    }
+}

spring-5-reactive/src/main/java/com/baeldung/reactive/responseheaders/filter/AddResponseHeaderWebFilter.java

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+package com.baeldung.reactive.responseheaders.filter;
+
+import org.springframework.stereotype.Component;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.WebFilter;
+import org.springframework.web.server.WebFilterChain;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class AddResponseHeaderWebFilter implements WebFilter {
+
+    @Override
+    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
+        exchange.getResponse()
+            .getHeaders()
+            .add("Baeldung-Example-Filter-Header", "Value-Filter");
+        return chain.filter(exchange);
+    }
+}

spring-5-reactive/src/main/java/com/baeldung/reactive/responseheaders/functional/handlers/ResponseHeaderHandler.java

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+package com.baeldung.reactive.responseheaders.functional.handlers;
+
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class ResponseHeaderHandler {
+    
+    public Mono<ServerResponse> useHandler(final ServerRequest request) {
+        String responseHeaderKey = "Baeldung-Example-Header";
+        String responseHeaderValue = "Value-Handler";
+        String responseBody = "Response with header using Handler";
+
+        return ServerResponse.ok()
+            .header(responseHeaderKey, responseHeaderValue)
+            .body(Mono.just(responseBody),String.class);
+    }
+}

spring-5-reactive/src/main/java/com/baeldung/reactive/responseheaders/functional/routers/ResponseHeadersRouterFunctions.java

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+package com.baeldung.reactive.responseheaders.functional.routers;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.function.server.RequestPredicates;
+import org.springframework.web.reactive.function.server.RouterFunction;
+import org.springframework.web.reactive.function.server.RouterFunctions;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import com.baeldung.reactive.responseheaders.functional.handlers.ResponseHeaderHandler;
+
+@Configuration
+public class ResponseHeadersRouterFunctions {
+
+    @Bean
+    public RouterFunction<ServerResponse> responseHeaderRoute(@Autowired ResponseHeaderHandler handler) {
+        return RouterFunctions.route(RequestPredicates.GET("/functional-response-header/single-handler"), handler::useHandler);
+    }
+}