BAEL-7196 Multiple Headers on WebClient (#18465)

* BAEL-7196 Multiple Headers on WebClient

* Rename test file

Author: apelan

spring-reactive-modules/spring-webflux/src/test/java/com/baeldung/spring/multipleheaders/MultipleHeadersUnitTest.java

@@ -0,0 +1,120 @@
+package com.baeldung.spring.multipleheaders;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.UUID;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.HttpStatusCode;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.reactive.function.client.ClientRequest;
+import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import okhttp3.mockwebserver.RecordedRequest;
+
+public class MultipleHeadersUnitTest {
+
+    private static final String RANDOM_UUID = UUID.randomUUID().toString();
+
+    private static MockWebServer mockWebServer;
+
+    @BeforeAll
+    static void setup() throws IOException {
+        mockWebServer = new MockWebServer();
+        mockWebServer.start();
+    }
+
+    @AfterAll
+    static void shutdown() throws IOException {
+        mockWebServer.shutdown();
+    }
+
+    @Test
+    public void givenRequestWithHeaders_whenSendingRequest_thenAssertHeadersAreSent() throws Exception {
+        mockWebServer.enqueue(new MockResponse().setResponseCode(HttpStatus.OK.value()));
+
+        WebClient client = WebClient.builder()
+            .baseUrl(mockWebServer.url("/").toString())
+            .build();
+
+        ResponseEntity<Void> response = client.get()
+            .headers(headers -> {
+                headers.put("X-Request-Id", Collections.singletonList(RANDOM_UUID));
+                headers.put("Custom-Header", Collections.singletonList("CustomValue"));
+            })
+            .retrieve()
+            .toBodilessEntity()
+            .block();
+
+        assertNotNull(response);
+        assertEquals(HttpStatusCode.valueOf(HttpStatus.OK.value()), response.getStatusCode());
+
+        RecordedRequest recordedRequest = mockWebServer.takeRequest();
+        assertEquals(RANDOM_UUID, recordedRequest.getHeader("X-Request-Id"));
+        assertEquals("CustomValue", recordedRequest.getHeader("Custom-Header"));
+    }
+
+    @Test
+    public void givenRequestWithDefaultHeaders_whenSendingRequest_thenAssertHeadersAreSent() throws Exception {
+        mockWebServer.enqueue(new MockResponse().setResponseCode(HttpStatus.OK.value()));
+
+        WebClient client = WebClient.builder()
+            .baseUrl(mockWebServer.url("/").toString())
+            .defaultHeaders(headers -> {
+                headers.put("X-Request-Id", Collections.singletonList(RANDOM_UUID));
+                headers.put("Custom-Header", Collections.singletonList("CustomValue"));
+            })
+            .build();
+
+        ResponseEntity<Void> response = client.get()
+            .retrieve()
+            .toBodilessEntity()
+            .block();
+
+        assertNotNull(response);
+        assertEquals(HttpStatusCode.valueOf(HttpStatus.OK.value()), response.getStatusCode());
+
+        RecordedRequest recordedRequest = mockWebServer.takeRequest();
+        assertEquals(RANDOM_UUID, recordedRequest.getHeader("X-Request-Id"));
+        assertEquals("CustomValue", recordedRequest.getHeader("Custom-Header"));
+    }
+
+    @Test
+    public void givenRequestWithDynamicHeaders_whenSendingRequest_thenAssertHeadersAreSent() throws Exception {
+        mockWebServer.enqueue(new MockResponse().setResponseCode(HttpStatus.OK.value()));
+
+        ExchangeFilterFunction dynamicHeadersFilter = (request, next) -> next.exchange(ClientRequest.from(request)
+            .headers(headers -> {
+                headers.put("X-Request-Id", Collections.singletonList(RANDOM_UUID));
+                headers.put("Custom-Header", Collections.singletonList("CustomValue"));
+            })
+            .build());
+
+        WebClient client = WebClient.builder()
+            .baseUrl(mockWebServer.url("/").toString())
+            .filter(dynamicHeadersFilter)
+            .build();
+
+        ResponseEntity<Void> response = client.get()
+            .retrieve()
+            .toBodilessEntity()
+            .block();
+
+        assertNotNull(response);
+        assertEquals(HttpStatusCode.valueOf(HttpStatus.OK.value()), response.getStatusCode());
+
+        RecordedRequest recordedRequest = mockWebServer.takeRequest();
+        assertEquals(RANDOM_UUID, recordedRequest.getHeader("X-Request-Id"));
+        assertEquals("CustomValue", recordedRequest.getHeader("Custom-Header"));
+    }
+
+}