BAEL-5182 code for webclient status code handling article (#11373)

* BAEL-5182 code for webclient status code handling article

* BAEL-5182 code for webclient status code handling article

* BAEL-5182 added different exceptions to make seperate examples clearer

Co-authored-by: Liam Garvie <liamgarvie@192.168.1.106>

spring-5-reactive-client/src/main/java/com/baeldung/webclient/status/WebClientStatusCodeHandler.java

@@ -0,0 +1,54 @@
+package com.baeldung.webclient.status;
+
+import com.baeldung.webclient.status.exception.BadRequestException;
+import com.baeldung.webclient.status.exception.ServerErrorException;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.reactive.function.client.ClientResponse;
+import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Mono;
+
+public class WebClientStatusCodeHandler {
+
+    public static Mono<String> getResponseBodyUsingExchangeFilterFunction(String uri) {
+        ExchangeFilterFunction errorResponseFilter = ExchangeFilterFunction
+            .ofResponseProcessor(WebClientStatusCodeHandler::exchangeFilterResponseProcessor);
+        return WebClient
+            .builder()
+            .filter(errorResponseFilter)
+            .build()
+            .post()
+            .uri(uri)
+            .retrieve()
+            .bodyToMono(String.class);
+    }
+
+    public static Mono<String> getResponseBodyUsingOnStatus(String uri) {
+        return WebClient
+            .builder()
+            .build()
+            .post()
+            .uri(uri)
+            .retrieve()
+            .onStatus(
+                HttpStatus.INTERNAL_SERVER_ERROR::equals,
+                response -> response.bodyToMono(String.class).map(ServerErrorException::new))
+            .onStatus(
+                HttpStatus.BAD_REQUEST::equals,
+                response -> response.bodyToMono(String.class).map(BadRequestException::new))
+            .bodyToMono(String.class);
+    }
+
+    private static Mono<ClientResponse> exchangeFilterResponseProcessor(ClientResponse response) {
+        HttpStatus status = response.statusCode();
+        if (HttpStatus.INTERNAL_SERVER_ERROR.equals(status)) {
+            return response.bodyToMono(String.class)
+                .flatMap(body -> Mono.error(new ServerErrorException(body)));
+        }
+        if (HttpStatus.BAD_REQUEST.equals(status)) {
+            return response.bodyToMono(String.class)
+                .flatMap(body -> Mono.error(new BadRequestException(body)));
+        }
+        return Mono.just(response);
+    }
+}

spring-5-reactive-client/src/main/java/com/baeldung/webclient/status/exception/BadRequestException.java

@@ -0,0 +1,7 @@
+package com.baeldung.webclient.status.exception;
+
+public class BadRequestException extends Exception {
+    public BadRequestException(String message) {
+        super(message);
+    }
+}

spring-5-reactive-client/src/main/java/com/baeldung/webclient/status/exception/ServerErrorException.java

@@ -0,0 +1,7 @@
+package com.baeldung.webclient.status.exception;
+
+public class ServerErrorException extends Exception {
+    public ServerErrorException(String message) {
+        super(message);
+    }
+}

spring-5-reactive-client/src/test/java/com/baeldung/webclient/WebClientStatusCodeHandlerIntegrationTest.java

@@ -0,0 +1,98 @@
+package com.baeldung.webclient;
+
+import com.baeldung.webclient.status.WebClientStatusCodeHandler;
+import com.github.tomakehurst.wiremock.WireMockServer;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.test.context.junit4.SpringRunner;
+import reactor.core.publisher.Mono;
+
+import static com.github.tomakehurst.wiremock.client.WireMock.aResponse;
+import static com.github.tomakehurst.wiremock.client.WireMock.configureFor;
+import static com.github.tomakehurst.wiremock.client.WireMock.post;
+import static com.github.tomakehurst.wiremock.client.WireMock.stubFor;
+import static com.github.tomakehurst.wiremock.client.WireMock.urlEqualTo;
+import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
+import static java.lang.String.format;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+@RunWith(SpringRunner.class)
+public class WebClientStatusCodeHandlerIntegrationTest {
+    private String baseUrl;
+    private WireMockServer wireMockServer;
+
+    @Before
+    public void setUp() {
+        wireMockServer = new WireMockServer(wireMockConfig().dynamicPort());
+        wireMockServer.start();
+        configureFor("localhost", wireMockServer.port());
+        baseUrl = format("http://localhost:%s", wireMockServer.port());
+    }
+
+    @After
+    public void tearDown() {
+        wireMockServer.stop();
+    }
+
+    @Test
+    public void whenResponseIs2XX_thenBothStatusHandlerAndExchangeFilterReturnEqualResponses() {
+        stubPostResponse("/success", 200, "success");
+
+        Mono<String> responseStatusHandler = WebClientStatusCodeHandler
+            .getResponseBodyUsingOnStatus(baseUrl + "/success");
+
+        Mono<String> responseExchangeFilter = WebClientStatusCodeHandler
+           .getResponseBodyUsingExchangeFilterFunction(baseUrl + "/success");
+
+        assertThat(responseStatusHandler.block())
+            .isEqualTo(responseExchangeFilter.block())
+            .isEqualTo("success");
+    }
+
+    @Test
+    public void whenResponseIs500_thenBothStatusHandlerAndExchangeFilterReturnEqualResponses() {
+        stubPostResponse("/server-error", 500, "Internal Server Error");
+
+        Mono<String> responseStatusHandler = WebClientStatusCodeHandler
+            .getResponseBodyUsingOnStatus(baseUrl + "/server-error");
+
+        Mono<String> responseExchangeFilter = WebClientStatusCodeHandler
+            .getResponseBodyUsingExchangeFilterFunction(baseUrl + "/server-error");
+
+        assertThatThrownBy(responseStatusHandler::block)
+            .isInstanceOf(Exception.class)
+            .hasMessageContaining("Internal Server Error");
+
+        assertThatThrownBy(responseExchangeFilter::block)
+            .isInstanceOf(Exception.class)
+            .hasMessageContaining("Internal Server Error");
+    }
+
+    @Test
+    public void whenResponseIs400_thenBothStatusHandlerAndExchangeFilterReturnEqualResponses() {
+        stubPostResponse("/client-error", 400, "Bad Request");
+
+        Mono<String> responseStatusHandler = WebClientStatusCodeHandler
+            .getResponseBodyUsingOnStatus(baseUrl + "/client-error");
+
+        Mono<String> responseExchangeFilter = WebClientStatusCodeHandler
+            .getResponseBodyUsingExchangeFilterFunction(baseUrl + "/client-error");
+
+        assertThatThrownBy(responseStatusHandler::block)
+            .isInstanceOf(Exception.class)
+            .hasMessageContaining("Bad Request");
+
+        assertThatThrownBy(responseExchangeFilter::block)
+            .isInstanceOf(Exception.class)
+            .hasMessageContaining("Bad Request");
+    }
+
+    private static void stubPostResponse(String url, int statusCode, String response) {
+        stubFor(post(urlEqualTo(url)).willReturn(aResponse()
+            .withStatus(statusCode)
+            .withBody(response)));
+    }
+}