fix(#524): return valid error even if request body is invalid

A valid GraphQL error response is returned with a descriptive
error message instead of HTTP 500 with internal details.

Details of the parse error is logged server-side.

Author: BlasiusSecundus

graphql-kickstart-spring-boot-autoconfigure-webflux/src/test/java/graphql/kickstart/spring/webflux/boot/InvalidJsonRequestTest.java

@@ -0,0 +1,42 @@
+package graphql.kickstart.spring.webflux.boot;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import org.assertj.core.util.Files;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class InvalidJsonRequestTest {
+
+  @Autowired private WebTestClient webTestClient;
+
+  @ParameterizedTest
+  @ValueSource(strings = {"\"false\":true", "not-a-json"})
+  @DisplayName("Should return valid response to a request with invalid JSON or non-JSON body.")
+  void testHandlingInvalidJsonRequest(String badRequestBody) throws IOException {
+    // GIVEN
+    final String expectedJson =
+        Files.contentOf(
+            new ClassPathResource("response-to-invalid-request.json").getFile(),
+            StandardCharsets.UTF_8);
+    // WHEN - THEN
+    webTestClient
+        .post()
+        .uri("/graphql")
+        .contentType(MediaType.APPLICATION_JSON)
+        .bodyValue(badRequestBody)
+        .exchange()
+        .expectStatus()
+        .isEqualTo(HttpStatus.OK)
+        .expectBody()
+        .json(expectedJson);
+  }
+}

graphql-kickstart-spring-boot-autoconfigure-webflux/src/test/resources/response-to-invalid-request.json

@@ -0,0 +1,9 @@
+{
+  "errors": [
+    {
+      "message": "Bad request - invalid request body.",
+      "locations": []
+    }
+  ],
+  "data": null
+}

graphql-kickstart-spring-support/src/main/java/graphql/kickstart/spring/AbstractGraphQLController.java

@@ -1,12 +1,15 @@
 package graphql.kickstart.spring;
 
+import graphql.ExecutionResultImpl;
 import graphql.kickstart.execution.GraphQLObjectMapper;
 import graphql.kickstart.execution.GraphQLRequest;
+import graphql.kickstart.execution.error.GenericGraphQLError;
 import java.io.IOException;
 import java.util.Collections;
 import java.util.Map;
 import java.util.Optional;
 import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
@@ -20,8 +23,11 @@
 import org.springframework.web.server.ServerWebExchange;
 
 @RequiredArgsConstructor
+@Slf4j
 public abstract class AbstractGraphQLController {
 
+  private static final String INVALID_REQUEST_BODY_MESSAGE = "Bad request - invalid request body.";
+
   private final GraphQLObjectMapper objectMapper;
 
   @PostMapping(
@@ -34,13 +40,17 @@ public Object graphqlPOST(
       @Nullable @RequestParam(value = "operationName", required = false) String operationName,
       @Nullable @RequestParam(value = "variables", required = false) String variablesJson,
       @Nullable @RequestBody(required = false) String body,
-      ServerWebExchange serverWebExchange)
-      throws IOException {
+      ServerWebExchange serverWebExchange) {
 
     body = Optional.ofNullable(body).orElse("");
 
     if (MediaType.APPLICATION_JSON.isCompatibleWith(contentType)) {
-      GraphQLRequest request = objectMapper.readGraphQLRequest(body);
+      GraphQLRequest request;
+      try {
+        request = objectMapper.readGraphQLRequest(body);
+      } catch (IOException e) {
+        return handleBodyParsingException(e, serverWebExchange);
+      }
       if (request.getQuery() == null) {
         request.setQuery("");
       }
@@ -95,4 +105,11 @@ protected abstract Object executeRequest(
       String operationName,
       Map<String, Object> variables,
       ServerWebExchange serverWebExchange);
+
+  protected Object handleBodyParsingException(
+      Exception exception, ServerWebExchange serverWebExchange) {
+    log.error("{} {}", INVALID_REQUEST_BODY_MESSAGE, exception.getMessage());
+    return objectMapper.createResultFromExecutionResult(
+        new ExecutionResultImpl(new GenericGraphQLError(INVALID_REQUEST_BODY_MESSAGE)));
+  }
 }