fix for issue #1398

Author: gracekarina

modules/swagger-parser-v3/src/main/java/io/swagger/v3/parser/util/OpenAPIDeserializer.java

@@ -2189,7 +2189,11 @@ public Schema getSchema(ObjectNode node, String location, ParseResult result){
 
         BigDecimal bigDecimal = getBigDecimal("multipleOf",node,false,location,result);
         if(bigDecimal != null) {
-            schema.setMultipleOf(bigDecimal);
+            if(bigDecimal.intValue() > 0) {
+                schema.setMultipleOf(bigDecimal);
+            }else{
+                result.warning(location,"multipleOf value must be > 0");
+            }
         }
 
         bigDecimal = getBigDecimal("maximum", node, false, location, result);

modules/swagger-parser-v3/src/test/java/io/swagger/v3/parser/test/OpenAPIV3ParserTest.java

@@ -82,6 +82,12 @@ public class OpenAPIV3ParserTest {
     protected int serverPort = getDynamicPort();
     protected WireMockServer wireMockServer;
 
+    @Test
+    public void testIssue1398() {
+        ParseOptions options = new ParseOptions();
+        SwaggerParseResult result = new OpenAPIV3Parser().readLocation("issue1398.yaml", null, options);
+        assertEquals(result.getMessages().get(0), "attribute paths.'/pet/{petId}'(get).parameters.[petId].schemas.multipleOf value must be > 0");
+    }
 
     @Test
     public void testIssue1367() {

modules/swagger-parser-v3/src/test/resources/issue1398.yaml

@@ -0,0 +1,26 @@
+openapi: 3.0.1
+info:
+  title: Swagger Petstore
+  description: 'This is a sample server Petstore server'
+  version: 1.0.0
+servers:
+  - url: http://mytestServer/{v1}
+    variables:
+      v2:
+        default: 'd'
+paths:
+  '/pet/{petId}':
+    get:
+      summary: Find pet by ID
+      description: Returns a single pet
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet to return
+          required: true
+          schema:
+            type : integer
+            multipleOf: -10
+      responses:
+        '200':
+          description: successful operation