[BUG][java][resttemplate] Fix NPE when query param with value null is exploded (#17568)

* Fix NPE when query param with value null is exploded

* Polish

* Add test

* Update tests

* Add integration test

modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/api.mustache

@@ -126,8 +126,10 @@ public class {{classname}} {
         final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();{{#hasQueryParams}}
 
-{{#queryParams}}{{#isExplode}}{{#hasVars}}{{#vars}}        localVarQueryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
+        {{#queryParams}}{{#isExplode}}{{#hasVars}}
-{{/vars}}{{/hasVars}}{{^hasVars}}        localVarQueryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
+        if ({{paramName}} != null) {
+        {{#vars}}    localVarQueryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}.{{getter}}()));
+        {{/vars}}}{{/hasVars}}{{^hasVars}}localVarQueryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
         {{/hasVars}}{{/isExplode}}{{^isExplode}}localVarQueryParams.putAll(apiClient.parameterToMultiValueMap({{#collectionFormat}}ApiClient.CollectionFormat.valueOf("{{{.}}}".toUpperCase(Locale.ROOT)){{/collectionFormat}}{{^collectionFormat}}null{{/collectionFormat}}, "{{baseName}}", {{paramName}}));
         {{/isExplode}}{{/queryParams}}{{/hasQueryParams}}{{#hasHeaderParams}}
 

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java

@@ -2938,4 +2938,32 @@ public class JavaClientCodegenTest {
         assertNotNull(apiFile);
         JavaFileAssert.assertThat(apiFile).fileContains(expectedInnerEnumLines);
     }
+
+    @Test
+    public void testQueryParamsExploded_whenQueryParamIsNull() throws IOException {
+
+        Map<String, Object> properties = new HashMap<>();
+        properties.put(CodegenConstants.API_PACKAGE, "xyz.abcdef.api");
+
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("java")
+                .setLibrary(JavaClientCodegen.RESTTEMPLATE)
+                .setAdditionalProperties(properties)
+                .setInputSpec("src/test/resources/3_0/issue_17555.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        validateJavaSourceFiles(files);
+
+
+        Path petApi = Paths.get(output + "/src/main/java/xyz/abcdef/api/DepartmentApi.java");
+        TestUtils.assertFileContains(petApi, "if (filter != null) {");
+    }
 }

modules/openapi-generator/src/test/resources/3_0/issue_17555.yaml

@@ -0,0 +1,51 @@
+openapi: 3.0.0
+info:
+  description: My description
+  version: 1.0.0
+  title: OpenAPI Petstore
+  license:
+    name: Apache-2.0
+    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
+tags:
+  - name: department
+    description: Everything about your Department
+paths:
+  /api/department/{departmentId}/teams:
+    get:
+      tags:
+        - Department
+      summary: Find Department Teams
+      operationId: findDepartmentTeams
+      description: Find Department Teams
+      parameters:
+        - $ref: '#/components/parameters/departmentIdParam'
+        - $ref: '#/components/parameters/teamQueryParam'
+      responses:
+        '200':
+          description: OK
+components:
+  schemas:
+    TeamCriteriaDTO:
+      type: object
+      title: TeamCriteriaDTO
+      properties:
+        key:
+          type: string
+        name:
+          type: string
+  parameters:
+    departmentIdParam:
+      name: departmentId
+      in: path
+      description: ID of the department to search
+      required: true
+      schema:
+        type: string
+    teamQueryParam:
+      name: filter
+      in: query
+      description: Fetch teams query
+      required: false
+      allowEmptyValue: true
+      schema:
+        $ref: '#/components/schemas/TeamCriteriaDTO'

samples/client/echo_api/java/resttemplate/src/main/java/org/openapitools/client/api/QueryApi.java

@@ -227,13 +227,15 @@ public class QueryApi {
         final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();
 
+        
+        if (queryObject != null) {
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "id", queryObject.getId()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "name", queryObject.getName()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "category", queryObject.getCategory()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "photoUrls", queryObject.getPhotoUrls()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "tags", queryObject.getTags()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "status", queryObject.getStatus()));
-
+        }
 
         final String[] localVarAccepts = { 
             "text/plain"
@@ -320,8 +322,10 @@ public class QueryApi {
         final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();
 
-        localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "values", queryObject.getValues()));
         
+        if (queryObject != null) {
+            localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "values", queryObject.getValues()));
+        }
 
         final String[] localVarAccepts = { 
             "text/plain"
@@ -364,13 +368,15 @@ public class QueryApi {
         final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
         final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();
 
+        
+        if (queryObject != null) {
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "id", queryObject.getId()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "name", queryObject.getName()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "category", queryObject.getCategory()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "photoUrls", queryObject.getPhotoUrls()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "tags", queryObject.getTags()));
             localVarQueryParams.putAll(apiClient.parameterToMultiValueMap(null, "status", queryObject.getStatus()));
-
+        }
 
         final String[] localVarAccepts = { 
             "text/plain"

samples/client/echo_api/java/resttemplate/src/test/java/org/openapitools/client/CustomTest.java

@@ -14,13 +14,15 @@
 package org.openapitools.client;
 
 import org.junit.Assert;
-import org.openapitools.client.api.*;
-import org.openapitools.client.model.*;
 import org.junit.Test;
-import org.junit.Ignore;
+import org.openapitools.client.api.BodyApi;
+import org.openapitools.client.api.QueryApi;
+import org.openapitools.client.model.Category;
+import org.openapitools.client.model.Pet;
 
-import java.io.IOException;
+import java.util.Arrays;
-import java.util.*;
+
+import static org.junit.Assert.assertNotNull;
 
 
 /**
@@ -43,7 +45,7 @@ public class CustomTest {
                 photoUrls(Arrays.asList(new String[]{"http://a.com", "http://b.com"})).category(new Category().id(987L).name("new category"));
 
         Pet p = bodyApi.testEchoBodyPet(pet);
-        Assert.assertNotNull(p);
+        assertNotNull(p);
         Assert.assertEquals("Hello World", p.getName());
         Assert.assertEquals(Long.valueOf(12345L), p.getId());
 
@@ -51,4 +53,9 @@ public class CustomTest {
         Pet p2 = bodyApi.testEchoBodyPet(null);
         Assert.assertNull(p2);
     }
+    
+    @Test
+    public void testQueryParamsExploded_whenQueryParamIsNull() {
+        assertNotNull(api.testQueryStyleFormExplodeTrueObject(null));
+    }
 }