Properly close resources when generating files #987 (#989)

Author: JamesPeters98

src/main/java/com/kobylynskyi/graphql/codegen/generators/FreeMarkerTemplateFilesCreator.java

@@ -9,6 +9,7 @@
 
 import java.io.File;
 import java.io.FileWriter;
+import java.io.IOException;
 import java.nio.file.FileAlreadyExistsException;
 import java.util.Map;
 
@@ -37,12 +38,18 @@ public static File create(MappingContext mappingContext,
         String fileName = dataModel.get(DataModelFields.CLASS_NAME) + language.getFileExtension();
         File fileOutputDir = getFileTargetDirectory(dataModel, mappingContext.getOutputDirectory());
         File javaSourceFile = new File(fileOutputDir, fileName);
+
         try {
             if (!javaSourceFile.createNewFile()) {
                 throw new FileAlreadyExistsException("File already exists: " + javaSourceFile.getPath());
             }
+        } catch (IOException e) {
+            throw new UnableToCreateFileException(e);
+        }
+
+        try (FileWriter fileWriter = new FileWriter(javaSourceFile)) {
             Template template = FreeMarkerTemplatesRegistry.getTemplateWithLang(language, templateType);
-            template.process(dataModel, new FileWriter(javaSourceFile));
+            template.process(dataModel, fileWriter);
         } catch (Exception e) {
             throw new UnableToCreateFileException(e);
         }