FIx issue #351

Author: João Dias

springdoc-openapi-common/src/main/java/org/springdoc/core/AbstractResponseBuilder.java

@@ -23,9 +23,7 @@
 import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.method.HandlerMethod;
 
-import java.lang.reflect.Method;
-import java.lang.reflect.ParameterizedType;
-import java.lang.reflect.Type;
+import java.lang.reflect.*;
 import java.util.*;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -39,9 +37,12 @@ public abstract class AbstractResponseBuilder {
 
     private final OperationBuilder operationBuilder;
 
-    protected AbstractResponseBuilder(OperationBuilder operationBuilder) {
+    private final List<ReturnTypeParser> returnTypeParsers;
+
+    protected AbstractResponseBuilder(OperationBuilder operationBuilder, List<ReturnTypeParser> returnTypeParsers) {
         super();
         this.operationBuilder = operationBuilder;
+        this.returnTypeParsers = returnTypeParsers;
     }
 
     public ApiResponses build(Components components, HandlerMethod handlerMethod, Operation operation,
@@ -203,7 +204,7 @@ private Set<io.swagger.v3.oas.annotations.responses.ApiResponse> getApiResponses
 
     private Content buildContent(Components components, Method method, String[] methodProduces, JsonView jsonView) {
         Content content = new Content();
-        Type returnType = method.getGenericReturnType();
+        Type returnType = getReturnType(method);
         if (isVoid(returnType)) {
             // if void, no content
             content = null;
@@ -219,6 +220,19 @@ private Content buildContent(Components components, Method method, String[] meth
         return content;
     }
 
+    private Type getReturnType(Method method) {
+        Type returnType = Object.class;
+        for (ReturnTypeParser returnTypeParser: returnTypeParsers) {
+            if (returnType.getTypeName().equals(Object.class.getTypeName())) {
+                returnType = returnTypeParser.getReturnType(method);
+            } else {
+                break;
+            }
+        }
+
+        return returnType;
+    }
+
     private Schema<?> calculateSchema(Components components, Type returnType, JsonView jsonView) {
         Schema<?> schemaN = null;
         if (isVoid(returnType)) {
@@ -328,4 +342,15 @@ private boolean isVoid(Type returnType) {
         return Void.TYPE.equals(returnType) || (returnType instanceof ParameterizedType
                 && Void.class.equals(((ParameterizedType) returnType).getActualTypeArguments()[0]));
     }
+
+    interface ReturnTypeParser {
+        Type getReturnType(Method method);
+    }
+
+    public static class GenericReturnTypeParser implements ReturnTypeParser {
+        @Override
+        public Type getReturnType(Method method) {
+            return method.getGenericReturnType();
+        }
+    }
 }

springdoc-openapi-common/src/main/java/org/springdoc/core/SpringDocConfiguration.java

@@ -79,6 +79,11 @@ public SecurityParser securityParser(PropertyResolverUtils propertyResolverUtils
         return new SecurityParser(propertyResolverUtils);
     }
 
+    @Bean
+    public AbstractResponseBuilder.GenericReturnTypeParser genericReturnTypeParser() {
+        return new AbstractResponseBuilder.GenericReturnTypeParser();
+    }
+
     static class ConditionOnCacheOrGroupedOpenApi extends AnyNestedCondition {
 
         ConditionOnCacheOrGroupedOpenApi() {

springdoc-openapi-kotlin/src/main/java/org/springdoc/core/KotlinCoroutinesReturnTypeParser.java

@@ -0,0 +1,33 @@
+package org.springdoc.core;
+
+import kotlin.coroutines.Continuation;
+import org.springdoc.core.customizers.OperationCustomizer;
+import org.springdoc.core.customizers.ParameterCustomizer;
+
+import java.lang.reflect.*;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+public class KotlinCoroutinesReturnTypeParser implements AbstractResponseBuilder.ReturnTypeParser {
+
+    @Override
+    public Type getReturnType(Method method) {
+        Type returnType = Object.class;
+        Optional<Parameter> continuationParameter = Arrays.stream(method.getParameters())
+                .filter((parameter) -> parameter.getType().getCanonicalName().equals(Continuation.class.getCanonicalName()))
+                .findFirst();
+
+        if (continuationParameter.isPresent()) {
+            Type continuationType = continuationParameter.get().getParameterizedType();
+            if (continuationType instanceof ParameterizedType) {
+                Type actualTypeArguments = ((ParameterizedType) continuationType).getActualTypeArguments()[0];
+                if (actualTypeArguments instanceof WildcardType) {
+                    returnType = ((WildcardType) actualTypeArguments).getLowerBounds()[0];
+                }
+            }
+        }
+
+        return returnType;
+    }
+}

springdoc-openapi-kotlin/src/main/java/org/springdoc/core/SpringDocKotlinConfiguration.java

@@ -18,11 +18,16 @@ public class SpringDocKotlinConfiguration {
 
     @Bean
     @Primary
-    KotlinCoroutinesRequestBuilder kotlinCoroutinesRequestBuilder(AbstractParameterBuilder parameterBuilder, RequestBodyBuilder requestBodyBuilder,
+    public KotlinCoroutinesRequestBuilder kotlinCoroutinesRequestBuilder(AbstractParameterBuilder parameterBuilder, RequestBodyBuilder requestBodyBuilder,
                                                                   OperationBuilder operationBuilder, Optional<List<OperationCustomizer>> operationCustomizers, Optional<List<ParameterCustomizer>> parameterCustomizers) {
         return new KotlinCoroutinesRequestBuilder(parameterBuilder, requestBodyBuilder,
                 operationBuilder, operationCustomizers, parameterCustomizers);
     }
 
+    @Bean
+    public KotlinCoroutinesReturnTypeParser kotlinCoroutinesReturnTypeParser() {
+        return new KotlinCoroutinesReturnTypeParser();
+    }
+
 
 }

springdoc-openapi-webflux-core/src/main/java/org/springdoc/core/ResponseBuilder.java

@@ -10,12 +10,13 @@
 import reactor.core.publisher.Mono;
 
 import java.lang.reflect.ParameterizedType;
+import java.util.List;
 
 @SuppressWarnings("rawtypes")
 public class ResponseBuilder extends AbstractResponseBuilder {
 
-    public ResponseBuilder(OperationBuilder operationBuilder) {
-        super(operationBuilder);
+    public ResponseBuilder(OperationBuilder operationBuilder, List<ReturnTypeParser> returnTypeParsers) {
+        super(operationBuilder, returnTypeParsers);
     }
 
     @Override

springdoc-openapi-webflux-core/src/main/java/org/springdoc/core/SpringDocWebFluxConfiguration.java

@@ -46,8 +46,8 @@ public RequestBuilder requestBuilder(AbstractParameterBuilder parameterBuilder,
     }
 
     @Bean
-    public ResponseBuilder responseBuilder(OperationBuilder operationBuilder) {
-        return new ResponseBuilder(operationBuilder);
+    public ResponseBuilder responseBuilder(OperationBuilder operationBuilder, List<AbstractResponseBuilder.ReturnTypeParser> returnTypeParsers) {
+        return new ResponseBuilder(operationBuilder, returnTypeParsers);
     }
 
 }

springdoc-openapi-webmvc-core/src/main/java/org/springdoc/core/ResponseBuilder.java

@@ -8,13 +8,14 @@
 
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
+import java.util.List;
 import java.util.concurrent.Callable;
 
 @SuppressWarnings("rawtypes")
 public class ResponseBuilder extends AbstractResponseBuilder {
 
-    public ResponseBuilder(OperationBuilder operationBuilder) {
-        super(operationBuilder);
+    public ResponseBuilder(OperationBuilder operationBuilder, List<ReturnTypeParser> returnTypeParsers) {
+        super(operationBuilder, returnTypeParsers);
     }
 
     @Override

springdoc-openapi-webmvc-core/src/main/java/org/springdoc/core/SpringDocWebMvcConfiguration.java

@@ -55,8 +55,8 @@ public RequestBuilder requestBuilder(AbstractParameterBuilder parameterBuilder,
 
     @Bean
     @ConditionalOnMissingBean
-    public ResponseBuilder responseBuilder(OperationBuilder operationBuilder) {
-        return new ResponseBuilder(operationBuilder);
+    public ResponseBuilder responseBuilder(OperationBuilder operationBuilder, List<AbstractResponseBuilder.ReturnTypeParser> returnTypeParsers) {
+        return new ResponseBuilder(operationBuilder, returnTypeParsers);
     }
 
     @Configuration