Use ParameterizedTypeReference in public-facing WebFlux APIs

This commit changes the use of `ResolvableType` to
`ParameterizedTypeReference` in all public-facing WebFlux APIs. This
change removes the necessity for providing the parameterized type
information twice: once for creating the `ResolvableType`, and once for
specifying a `BodyExtractor`.

Issue: SPR-15636

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyExtractorsTests.java

@@ -21,6 +21,7 @@ import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -32,6 +33,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.codec.ByteBufferDecoder;
 import org.springframework.core.codec.StringDecoder;
 import org.springframework.core.io.buffer.DataBuffer;
@@ -120,6 +122,28 @@ public class BodyExtractorsTests {
 				.verify();
 	}
 
+	@Test
+	public void toMonoParameterizedTypeReference() throws Exception {
+		ParameterizedTypeReference<Map<String, String>> typeReference = new ParameterizedTypeReference<Map<String, String>>() {};
+		BodyExtractor<Mono<Map<String, String>>, ReactiveHttpInputMessage> extractor = BodyExtractors.toMono(typeReference);
+
+		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+		DefaultDataBuffer dataBuffer =
+				factory.wrap(ByteBuffer.wrap("{\"username\":\"foo\",\"password\":\"bar\"}".getBytes(StandardCharsets.UTF_8)));
+		Flux<DataBuffer> body = Flux.just(dataBuffer);
+
+		MockServerHttpRequest request = MockServerHttpRequest.post("/").contentType(MediaType.APPLICATION_JSON).body(body);
+		Mono<Map<String, String>> result = extractor.extract(request, this.context);
+
+		Map<String, String > expected = new LinkedHashMap<>();
+		expected.put("username", "foo");
+		expected.put("password", "bar");
+		StepVerifier.create(result)
+				.expectNext(expected)
+				.expectComplete()
+				.verify();
+	}
+
 	@Test
 	public void toMonoWithHints() throws Exception {
 		BodyExtractor<Mono<User>, ReactiveHttpInputMessage> extractor = BodyExtractors.toMono(User.class);

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DefaultEntityResponseBuilderTests.java

@@ -30,7 +30,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
-import org.springframework.core.ResolvableType;
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
@@ -70,10 +70,10 @@ public class DefaultEntityResponseBuilderTests {
 	}
 
 	@Test
-	public void fromPublisherResolvableType() throws Exception {
+	public void fromPublisher() throws Exception {
 		Flux<String> body = Flux.just("foo", "bar");
-		ResolvableType type = ResolvableType.forClass(String.class);
-		EntityResponse<Flux<String>> response = EntityResponse.fromPublisher(body, type).build().block();
+		ParameterizedTypeReference<String> typeReference = new ParameterizedTypeReference<String>() {};
+		EntityResponse<Flux<String>> response = EntityResponse.fromPublisher(body, typeReference).build().block();
 		assertSame(body, response.entity());
 	}
 

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/SseHandlerFunctionIntegrationTests.java

@@ -24,15 +24,15 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.codec.ServerSentEvent;
 import org.springframework.web.reactive.function.client.WebClient;
 
 import static org.junit.Assert.*;
-import static org.springframework.core.ResolvableType.*;
-import static org.springframework.http.MediaType.*;
-import static org.springframework.web.reactive.function.BodyExtractors.*;
-import static org.springframework.web.reactive.function.BodyInserters.*;
-import static org.springframework.web.reactive.function.server.RouterFunctions.*;
+import static org.springframework.http.MediaType.TEXT_EVENT_STREAM;
+import static org.springframework.web.reactive.function.BodyExtractors.toFlux;
+import static org.springframework.web.reactive.function.BodyInserters.fromServerSentEvents;
+import static org.springframework.web.reactive.function.server.RouterFunctions.route;
 
 /**
  * @author Arjen Poutsma
@@ -94,7 +94,7 @@ public class SseHandlerFunctionIntegrationTests extends AbstractRouterFunctionIn
 				.accept(TEXT_EVENT_STREAM)
 				.exchange()
 				.flatMapMany(response -> response.body(toFlux(
-						forClassWithGenerics(ServerSentEvent.class, String.class))));
+						new ParameterizedTypeReference<ServerSentEvent<String>>() {})));
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SseIntegrationTests.java

@@ -26,6 +26,7 @@ import reactor.test.StepVerifier;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.core.ResolvableType;
 import org.springframework.http.codec.ServerSentEvent;
 import org.springframework.http.server.reactive.AbstractHttpHandlerIntegrationTests;
@@ -38,9 +39,9 @@ import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
 
 import static org.junit.Assert.*;
-import static org.springframework.core.ResolvableType.*;
-import static org.springframework.http.MediaType.*;
-import static org.springframework.web.reactive.function.BodyExtractors.*;
+import static org.springframework.core.ResolvableType.forClassWithGenerics;
+import static org.springframework.http.MediaType.TEXT_EVENT_STREAM;
+import static org.springframework.web.reactive.function.BodyExtractors.toFlux;
 
 /**
  * @author Sebastien Deleuze
@@ -106,7 +107,7 @@ public class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 				.uri("/event")
 				.accept(TEXT_EVENT_STREAM)
 				.exchange()
-				.flatMapMany(response -> response.body(toFlux(type)));
+				.flatMapMany(response -> response.body(toFlux(new ParameterizedTypeReference<ServerSentEvent<String>>() {})));
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {
@@ -133,8 +134,7 @@ public class SseIntegrationTests extends AbstractHttpHandlerIntegrationTests {
 				.uri("/event")
 				.accept(TEXT_EVENT_STREAM)
 				.exchange()
-				.flatMapMany(response -> response.body(toFlux(
-						forClassWithGenerics(ServerSentEvent.class, String.class))));
+				.flatMapMany(response -> response.body(toFlux(new ParameterizedTypeReference<ServerSentEvent<String>>() {})));
 
 		StepVerifier.create(result)
 				.consumeNextWith( event -> {