[JAVA][native] import the auto generated supporting JSON class only when discriminator is needed

Created by: MosheElisha

Import the auto generated supporting JSON class only when generateSupportingFiles is true.

Closes #8027 (closed)

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

  Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master, 5.1.x, 6.0.x
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

modules/openapi-generator/src/main/resources/Java/libraries/native/model.mustache

@@ -46,7 +46,6 @@ import javax.validation.Valid;
 {{#performBeanValidation}}
 import org.hibernate.validator.constraints.*;
 {{/performBeanValidation}}
-import {{invokerPackage}}.JSON;
 
 {{#models}}
 {{#model}}

modules/openapi-generator/src/main/resources/Java/libraries/native/pojo.mustache

+{{#discriminator}}
+import {{invokerPackage}}.JSON;
+{{/discriminator}}
 /**
  * {{#description}}{{.}}{{/description}}{{^description}}{{classname}}{{/description}}
  */{{#description}}

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

@@ -446,6 +446,38 @@ public class JavaClientCodegenTest {
                 "import java.net.http.HttpRequest;");
     }
 
+    @Test
+    public void testJdkHttpClientWithAndWithoutDiscriminator() throws Exception {
+        Map<String, Object> properties = new HashMap<>();
+        properties.put(CodegenConstants.API_PACKAGE, "xyz.abcdef.api");
+        properties.put(CodegenConstants.MODEL_PACKAGE, "xyz.abcdef.model");
+        properties.put(CodegenConstants.INVOKER_PACKAGE, "xyz.abcdef.invoker");
+
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("java")
+                .setLibrary(JavaClientCodegen.NATIVE)
+                .setAdditionalProperties(properties)
+                .setInputSpec("src/test/resources/2_0/petstore-with-fake-endpoints-models-for-testing.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        Assert.assertEquals(files.size(), 156);
+        validateJavaSourceFiles(files);
+
+        TestUtils.assertFileContains(Paths.get(output + "/src/main/java/xyz/abcdef/model/Dog.java"),
+                "import xyz.abcdef.invoker.JSON;");
+        TestUtils.assertFileNotContains(Paths.get(output + "/src/main/java/xyz/abcdef/model/DogAllOf.java"),
+                "import xyz.abcdef.invoker.JSON;");
+    }
+
     @Test
     public void testJdkHttpAsyncClient() throws Exception {
         Map<String, Object> properties = new HashMap<>();

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/AdditionalPropertiesAnyType.java

@@ -31,7 +31,6 @@ import io.swagger.annotations.ApiModelProperty;
 import java.util.HashMap;
 import java.util.Map;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
-import org.openapitools.client.JSON;
 
 
 /**

samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/AdditionalPropertiesArray.java

@@ -32,7 +32,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
-import org.openapitools.client.JSON;
 
 
 /**