Auto-configure schema printer endpoint

This commit configuresa new endpoint for printing in text format the
resolved GraphQL schema.
This endpoint is exposed by default under "/graphql/schema" and must be
enabled with "spring.graphql.schema.printer=true".

See gh-29140

Author: bclozel

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/GraphQlProperties.java

@@ -60,6 +60,8 @@ public static class Schema {
 		 */
 		private String[] fileExtensions = new String[] { ".graphqls", ".gqls" };
 
+		private final Printer printer = new Printer();
+
 		public String[] getLocations() {
 			return this.locations;
 		}
@@ -81,6 +83,28 @@ private String[] appendSlashIfNecessary(String[] locations) {
 					.toArray(String[]::new);
 		}
 
+		public Printer getPrinter() {
+			return this.printer;
+		}
+
+		public static class Printer {
+
+			/**
+			 * Whether the endpoint that prints the schema is enabled. Schema is available
+			 * under spring.graphql.path + "/schema".
+			 */
+			private boolean enabled = false;
+
+			public boolean isEnabled() {
+				return this.enabled;
+			}
+
+			public void setEnabled(boolean enabled) {
+				this.enabled = enabled;
+			}
+
+		}
+
 	}
 
 }

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfiguration.java

@@ -40,6 +40,7 @@
 import org.springframework.graphql.web.WebGraphQlHandler;
 import org.springframework.graphql.web.WebInterceptor;
 import org.springframework.graphql.web.webflux.GraphQlHttpHandler;
+import org.springframework.graphql.web.webflux.SchemaHandler;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
@@ -96,6 +97,11 @@ public RouterFunction<ServerResponse> graphQlEndpoint(GraphQlHttpHandler handler
 				.POST(graphQLPath, accept(MediaType.APPLICATION_JSON).and(contentType(MediaType.APPLICATION_JSON)),
 						handler::handleRequest);
 
+		if (properties.getSchema().getPrinter().isEnabled()) {
+			SchemaHandler schemaHandler = new SchemaHandler(graphQlSource);
+			builder = builder.GET(graphQLPath + "/schema", schemaHandler::handleRequest);
+		}
+
 		return builder.build();
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java

@@ -41,6 +41,7 @@
 import org.springframework.graphql.web.WebGraphQlHandler;
 import org.springframework.graphql.web.WebInterceptor;
 import org.springframework.graphql.web.webmvc.GraphQlHttpHandler;
+import org.springframework.graphql.web.webmvc.SchemaHandler;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
@@ -97,6 +98,11 @@ public RouterFunction<ServerResponse> graphQlRouterFunction(GraphQlHttpHandler h
 				.POST(graphQLPath, RequestPredicates.contentType(MediaType.APPLICATION_JSON)
 						.and(RequestPredicates.accept(MediaType.APPLICATION_JSON)), handler::handleRequest);
 
+		if (properties.getSchema().getPrinter().isEnabled()) {
+			SchemaHandler schemaHandler = new SchemaHandler(graphQlSource);
+			builder = builder.GET(graphQLPath + "/schema", schemaHandler::handleRequest);
+		}
+
 		return builder.build();
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/reactive/GraphQlWebFluxAutoConfigurationTests.java

@@ -38,6 +38,8 @@
 import org.springframework.http.MediaType;
 import org.springframework.test.web.reactive.server.WebTestClient;
 
+import static org.hamcrest.Matchers.containsString;
+
 /**
  * Tests for {@link GraphQlWebFluxAutoConfiguration}
  *
@@ -51,8 +53,8 @@ class GraphQlWebFluxAutoConfigurationTests {
 			.withConfiguration(AutoConfigurations.of(HttpHandlerAutoConfiguration.class, WebFluxAutoConfiguration.class,
 					CodecsAutoConfiguration.class, JacksonAutoConfiguration.class, GraphQlAutoConfiguration.class,
 					GraphQlWebFluxAutoConfiguration.class))
-			.withUserConfiguration(DataFetchersConfiguration.class, CustomWebInterceptor.class)
-			.withPropertyValues("spring.main.web-application-type=reactive");
+			.withUserConfiguration(DataFetchersConfiguration.class, CustomWebInterceptor.class).withPropertyValues(
+					"spring.main.web-application-type=reactive", "spring.graphql.schema.printer.enabled=true");
 
 	@Test
 	void simpleQueryShouldWork() {
@@ -92,6 +94,13 @@ void shouldConfigureWebInterceptors() {
 		});
 	}
 
+	@Test
+	void shouldExposeSchemaEndpoint() {
+		testWithWebClient((client) -> client.get().uri("/schema").accept(MediaType.ALL).exchange()
+				.expectStatus().isOk().expectHeader().contentType(MediaType.TEXT_PLAIN).expectBody(String.class)
+				.value(containsString("type Book")));
+	}
+
 	private void testWithWebClient(Consumer<WebTestClient> consumer) {
 		this.contextRunner.run((context) -> {
 			WebTestClient client = WebTestClient.bindToApplicationContext(context).configureClient()

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.graphql.servlet;
 
 import graphql.schema.idl.TypeRuntimeWiring;
+import org.hamcrest.Matchers;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
@@ -56,8 +57,8 @@ class GraphQlWebMvcAutoConfigurationTests {
 					AutoConfigurations.of(DispatcherServletAutoConfiguration.class, WebMvcAutoConfiguration.class,
 							HttpMessageConvertersAutoConfiguration.class, JacksonAutoConfiguration.class,
 							GraphQlAutoConfiguration.class, GraphQlWebMvcAutoConfiguration.class))
-			.withUserConfiguration(DataFetchersConfiguration.class, CustomWebInterceptor.class)
-			.withPropertyValues("spring.main.web-application-type=servlet");
+			.withUserConfiguration(DataFetchersConfiguration.class, CustomWebInterceptor.class).withPropertyValues(
+					"spring.main.web-application-type=servlet", "spring.graphql.schema.printer.enabled=true");
 
 	@Test
 	void simpleQueryShouldWork() {
@@ -99,6 +100,13 @@ void shouldConfigureWebInterceptors() {
 		});
 	}
 
+	@Test
+	void shouldExposeSchemaEndpoint() {
+		testWith((mockMvc) -> mockMvc.perform(get("/graphql/schema")).andExpect(status().isOk())
+				.andExpect(content().contentType(MediaType.TEXT_PLAIN))
+				.andExpect(content().string(Matchers.containsString("type Book"))));
+	}
+
 	private void testWith(MockMvcConsumer mockMvcConsumer) {
 		this.contextRunner.run((context) -> {
 			MediaType mediaType = MediaType.APPLICATION_JSON;