Update RestTestClient builder hierarchy

Add concrete classes with specified generics for each MockMvc setup
Ensure Builder methods return the concrete class

See gh-34428

Author: rstoyanchev

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -155,7 +155,7 @@ public interface WebTestClient {
 
 
 	/**
-	 * Return a builder to mutate properties of this web test client.
+	 * Return a builder to mutate properties of this test client.
 	 */
 	Builder mutate();
 
@@ -171,8 +171,6 @@ public interface WebTestClient {
 	WebTestClient mutateWith(WebTestClientConfigurer configurer);
 
 
-	// Static factory methods
-
 	/**
 	 * Use this server setup to test one {@code @Controller} at a time.
 	 * This option loads the default configuration of

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultMockServerBuilder.java

@@ -18,9 +18,20 @@
 
 import java.util.function.Consumer;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.client.ClientHttpRequestFactory;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MockMvcBuilder;
+import org.springframework.test.web.servlet.setup.DefaultMockMvcBuilder;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.test.web.servlet.setup.RouterFunctionMockMvcBuilder;
+import org.springframework.test.web.servlet.setup.StandaloneMockMvcBuilder;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.client.RestClient;
+import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.servlet.function.RouterFunction;
 import org.springframework.web.util.UriBuilderFactory;
 
 /**
@@ -33,7 +44,7 @@
  */
 class DefaultRestTestClientBuilder<B extends RestTestClient.Builder<B>> implements RestTestClient.Builder<B> {
 
-	protected final RestClient.Builder restClientBuilder;
+	private final RestClient.Builder restClientBuilder;
 
 
 	DefaultRestTestClientBuilder() {
@@ -46,49 +57,110 @@ class DefaultRestTestClientBuilder<B extends RestTestClient.Builder<B>> implemen
 
 
 	@Override
-	public RestTestClient.Builder<B> baseUrl(String baseUrl) {
+	public <T extends B> T baseUrl(String baseUrl) {
 		this.restClientBuilder.baseUrl(baseUrl);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> uriBuilderFactory(UriBuilderFactory uriFactory) {
+	public <T extends B> T uriBuilderFactory(UriBuilderFactory uriFactory) {
 		this.restClientBuilder.uriBuilderFactory(uriFactory);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> defaultHeader(String headerName, String... headerValues) {
+	public <T extends B> T defaultHeader(String headerName, String... headerValues) {
 		this.restClientBuilder.defaultHeader(headerName, headerValues);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> defaultHeaders(Consumer<HttpHeaders> headersConsumer) {
+	public <T extends B> T defaultHeaders(Consumer<HttpHeaders> headersConsumer) {
 		this.restClientBuilder.defaultHeaders(headersConsumer);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> defaultCookie(String cookieName, String... cookieValues) {
+	public <T extends B> T defaultCookie(String cookieName, String... cookieValues) {
 		this.restClientBuilder.defaultCookie(cookieName, cookieValues);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer) {
+	public <T extends B> T defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer) {
 		this.restClientBuilder.defaultCookies(cookiesConsumer);
-		return this;
+		return self();
 	}
 
 	@Override
-	public RestTestClient.Builder<B> apply(Consumer<RestTestClient.Builder<B>> builderConsumer) {
+	public <T extends B> T apply(Consumer<RestTestClient.Builder<B>> builderConsumer) {
 		builderConsumer.accept(this);
-		return this;
+		return self();
+	}
+
+	@SuppressWarnings("unchecked")
+	protected <T extends B> T self() {
+		return (T) this;
+	}
+
+	protected void setClientHttpRequestFactory(ClientHttpRequestFactory requestFactory) {
+		this.restClientBuilder.requestFactory(requestFactory);
 	}
 
 	@Override
 	public RestTestClient build() {
 		return new DefaultRestTestClient(this.restClientBuilder);
 	}
+
+
+	static class AbstractMockMvcSetupBuilder<S extends RestTestClient.Builder<S>, M extends MockMvcBuilder>
+			extends DefaultRestTestClientBuilder<S> implements RestTestClient.MockMvcSetupBuilder<S, M> {
+
+		private final M mockMvcBuilder;
+
+		public AbstractMockMvcSetupBuilder(M mockMvcBuilder) {
+			this.mockMvcBuilder = mockMvcBuilder;
+		}
+
+		public <T extends S> T configureServer(Consumer<M> consumer) {
+			consumer.accept(this.mockMvcBuilder);
+			return self();
+		}
+
+		@Override
+		public RestTestClient build() {
+			MockMvc mockMvc = this.mockMvcBuilder.build();
+			setClientHttpRequestFactory(new MockMvcClientHttpRequestFactory(mockMvc));
+			return super.build();
+		}
+	}
+
+
+	static class DefaultStandaloneSetupBuilder extends AbstractMockMvcSetupBuilder<RestTestClient.StandaloneSetupBuilder, StandaloneMockMvcBuilder>
+			implements RestTestClient.StandaloneSetupBuilder {
+
+		DefaultStandaloneSetupBuilder(Object... controllers) {
+			super(MockMvcBuilders.standaloneSetup(controllers));
+		}
+	}
+
+
+	static class DefaultRouterFunctionSetupBuilder extends AbstractMockMvcSetupBuilder<RestTestClient.RouterFunctionSetupBuilder, RouterFunctionMockMvcBuilder>
+			implements RestTestClient.RouterFunctionSetupBuilder {
+
+		DefaultRouterFunctionSetupBuilder(RouterFunction<?>... routerFunctions) {
+			super(MockMvcBuilders.routerFunctions(routerFunctions));
+		}
+
+	}
+
+
+	static class DefaultWebAppContextSetupBuilder extends AbstractMockMvcSetupBuilder<RestTestClient.WebAppContextSetupBuilder, DefaultMockMvcBuilder>
+			implements RestTestClient.WebAppContextSetupBuilder {
+
+		DefaultWebAppContextSetupBuilder(WebApplicationContext context) {
+			super(MockMvcBuilders.webAppContextSetup(context));
+		}
+	}
+
 }

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java

@@ -37,7 +37,6 @@
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MockMvcBuilder;
 import org.springframework.test.web.servlet.setup.DefaultMockMvcBuilder;
-import org.springframework.test.web.servlet.setup.MockMvcBuilders;
 import org.springframework.test.web.servlet.setup.RouterFunctionMockMvcBuilder;
 import org.springframework.test.web.servlet.setup.StandaloneMockMvcBuilder;
 import org.springframework.util.MultiValueMap;
@@ -51,6 +50,8 @@
  * Client for testing web servers.
  *
  * @author Rob Worsnop
+ * @author Rossen Stoyanchev
+ * @since 7.0
  */
 public interface RestTestClient {
 
@@ -126,9 +127,8 @@ public interface RestTestClient {
 	 * {@link org.springframework.test.web.servlet.setup.MockMvcBuilders#standaloneSetup(Object...)}
 	 * to initialize {@link MockMvc}.
 	 */
-	static MockServerBuilder<StandaloneMockMvcBuilder> standaloneSetup(Object... controllers) {
-		StandaloneMockMvcBuilder builder = MockMvcBuilders.standaloneSetup(controllers);
-		return new DefaultMockServerBuilder<>(builder);
+	static StandaloneSetupBuilder bindToController(Object... controllers) {
+		return new DefaultRestTestClientBuilder.DefaultStandaloneSetupBuilder(controllers);
 	}
 
 	/**
@@ -138,9 +138,8 @@ static MockServerBuilder<StandaloneMockMvcBuilder> standaloneSetup(Object... con
 	 * {@link org.springframework.test.web.servlet.setup.MockMvcBuilders#routerFunctions(RouterFunction[])}
 	 * to initialize {@link MockMvc}.
 	 */
-	static MockServerBuilder<RouterFunctionMockMvcBuilder> bindToRouterFunction(RouterFunction<?>... routerFunctions) {
-		RouterFunctionMockMvcBuilder builder = MockMvcBuilders.routerFunctions(routerFunctions);
-		return new DefaultMockServerBuilder<>(builder);
+	static RouterFunctionSetupBuilder bindToRouterFunction(RouterFunction<?>... routerFunctions) {
+		return new DefaultRestTestClientBuilder.DefaultRouterFunctionSetupBuilder(routerFunctions);
 	}
 
 	/**
@@ -151,16 +150,15 @@ static MockServerBuilder<RouterFunctionMockMvcBuilder> bindToRouterFunction(Rout
 	 * {@link org.springframework.test.web.servlet.setup.MockMvcBuilders#webAppContextSetup(WebApplicationContext)}
 	 * to initialize {@code MockMvc}.
 	 */
-	static MockServerBuilder<DefaultMockMvcBuilder> bindToApplicationContext(WebApplicationContext context) {
-		DefaultMockMvcBuilder builder = MockMvcBuilders.webAppContextSetup(context);
-		return new DefaultMockServerBuilder<>(builder);
+	static WebAppContextSetupBuilder bindToApplicationContext(WebApplicationContext context) {
+		return new DefaultRestTestClientBuilder.DefaultWebAppContextSetupBuilder(context);
 	}
 
 	/**
 	 * Begin creating a {@link RestTestClient} by providing an already
 	 * initialized {@link MockMvc} instance to use as the server.
 	 */
-	static <B extends Builder<B>> Builder<B> bindTo(MockMvc mockMvc) {
+	static Builder<?> bindTo(MockMvc mockMvc) {
 		ClientHttpRequestFactory requestFactory = new MockMvcClientHttpRequestFactory(mockMvc);
 		return RestTestClient.bindToServer(requestFactory);
 	}
@@ -175,15 +173,15 @@ static <B extends Builder<B>> Builder<B> bindTo(MockMvc mockMvc) {
 	 * </pre>
 	 * @return chained API to customize client config
 	 */
-	static <B extends Builder<B>> Builder<B> bindToServer() {
+	static Builder<?> bindToServer() {
 		return new DefaultRestTestClientBuilder<>();
 	}
 
 	/**
 	 * A variant of {@link #bindToServer()} with a pre-configured request factory.
 	 * @return chained API to customize client config
 	 */
-	static <B extends Builder<B>> Builder<B> bindToServer(ClientHttpRequestFactory requestFactory) {
+	static Builder<?> bindToServer(ClientHttpRequestFactory requestFactory) {
 		return new DefaultRestTestClientBuilder<>(RestClient.builder().requestFactory(requestFactory));
 	}
 
@@ -195,20 +193,20 @@ interface Builder<B extends Builder<B>> {
 		 * {@link RestClient#create(String)
 		 * WebClient.create(String)}.
 		 */
-		Builder<B> baseUrl(String baseUrl);
+		<T extends B> T baseUrl(String baseUrl);
 
 		/**
 		 * Provide a pre-configured {@link UriBuilderFactory} instance as an
 		 * alternative to and effectively overriding {@link #baseUrl(String)}.
 		 */
-		Builder<B> uriBuilderFactory(UriBuilderFactory uriBuilderFactory);
+		<T extends B> T uriBuilderFactory(UriBuilderFactory uriBuilderFactory);
 
 		/**
 		 * Add the given header to all requests that haven't added it.
 		 * @param headerName   the header name
 		 * @param headerValues the header values
 		 */
-		Builder<B> defaultHeader(String headerName, String... headerValues);
+		<T extends B> T defaultHeader(String headerName, String... headerValues);
 
 		/**
 		 * Manipulate the default headers with the given consumer. The
@@ -219,14 +217,14 @@ interface Builder<B extends Builder<B>> {
 		 * @param headersConsumer a function that consumes the {@code HttpHeaders}
 		 * @return this builder
 		 */
-		Builder<B> defaultHeaders(Consumer<HttpHeaders> headersConsumer);
+		<T extends B> T defaultHeaders(Consumer<HttpHeaders> headersConsumer);
 
 		/**
 		 * Add the given cookie to all requests.
 		 * @param cookieName   the cookie name
 		 * @param cookieValues the cookie values
 		 */
-		Builder<B> defaultCookie(String cookieName, String... cookieValues);
+		<T extends B> T defaultCookie(String cookieName, String... cookieValues);
 
 		/**
 		 * Manipulate the default cookies with the given consumer. The
@@ -237,29 +235,41 @@ interface Builder<B extends Builder<B>> {
 		 * @param cookiesConsumer a function that consumes the cookies map
 		 * @return this builder
 		 */
-		Builder<B> defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer);
+		<T extends B> T defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer);
 
 		/**
 		 * Apply the given {@code Consumer} to this builder instance.
 		 * <p>This can be useful for applying pre-packaged customizations.
 		 * @param builderConsumer the consumer to apply
 		 */
-		Builder<B> apply(Consumer<Builder<B>> builderConsumer);
+		<T extends B> T apply(Consumer<Builder<B>> builderConsumer);
 
 		/**
 		 * Build the {@link RestTestClient} instance.
 		 */
 		RestTestClient build();
+ 	}
+
+
+	interface MockMvcSetupBuilder<B extends Builder<B>, M extends MockMvcBuilder> extends Builder<B> {
+
+		<T extends B> T configureServer(Consumer<M> consumer);
+	}
+
+
+	interface StandaloneSetupBuilder extends MockMvcSetupBuilder<StandaloneSetupBuilder, StandaloneMockMvcBuilder> {
 	}
 
 
-	interface MockServerBuilder<M extends MockMvcBuilder> extends Builder<MockServerBuilder<M>> {
+	interface RouterFunctionSetupBuilder extends MockMvcSetupBuilder<RouterFunctionSetupBuilder, RouterFunctionMockMvcBuilder> {
+	}
 
-		MockServerBuilder<M> configureServer(Consumer<M> consumer);
 
+	interface WebAppContextSetupBuilder extends MockMvcSetupBuilder<WebAppContextSetupBuilder, DefaultMockMvcBuilder> {
 	}
 
 
+
 	/**
 	 * Specification for providing the URI of a request.
 	 *

spring-test/src/main/java/org/springframework/test/web/servlet/client/RestTestClient.java

@@ -48,7 +48,7 @@
 class JsonPathAssertionTests {
 
 	private final RestTestClient client =
-			RestTestClient.standaloneSetup(new MusicController())
+			RestTestClient.bindToController(new MusicController())
 					.configureServer(builder ->
 							builder.alwaysExpect(status().isOk())
 									.alwaysExpect(content().contentType(MediaType.APPLICATION_JSON))