Fixes after code review: added checking for singleton pattern, added @…

…target annotation, changed order in getInstatnce() method, gathered exceptions in ReflectiveOperationException

src/main/java/mate.academy/Main.java

@@ -11,6 +11,13 @@ public static void main(String[] args) {
         // Please test your Injector here. Feel free to push this class as a part of your solution
         Injector injector = Injector.getInjector();
         ProductService productService = (ProductService) injector.getInstance(ProductService.class);
+
+        // Checking the singleton pattern (on AI mentor request)
+        Injector injectorSecond = Injector.getInjector();
+        if (!injector.equals(injectorSecond)) {
+            throw new RuntimeException("The singleton pattern doesn't work correctly");
+        }
+
         List<Product> products = productService.getAllFromFile("products.txt");
         products.forEach(System.out::println);
     }

src/main/java/mate.academy/lib/Component.java

@@ -1,8 +1,11 @@
 package mate.academy.lib;
 
+import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
 
 @Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
 public @interface Component {
 }

src/main/java/mate.academy/lib/Injector.java

@@ -19,10 +19,13 @@ public Object getInstance(Class<?> interfaceClazz) {
             Object clazzImplementationInstance = null;
             Class<?> clazz = findImplementation(interfaceClazz);
             Field[] declaredFields = clazz.getDeclaredFields();
+            if (clazzImplementationInstance == null) {
+                clazzImplementationInstance = createNewInstance(clazz);
+            }
+            clazzImplementationInstance = createNewInstance(clazz);
             for (Field field : declaredFields) {
                 if (field.isAnnotationPresent(Inject.class)) {
                     Object fieldInstance = getInstance(field.getType());
-                    clazzImplementationInstance = createNewInstance(clazz);
                     field.setAccessible(true);
                     try {
                         field.set(clazzImplementationInstance, fieldInstance);
@@ -32,12 +35,7 @@ public Object getInstance(Class<?> interfaceClazz) {
                     }
                 }
             }
-            if (clazzImplementationInstance == null) {
-                clazzImplementationInstance = createNewInstance(clazz);
-
-            }
             return clazzImplementationInstance;
-
         } else {
             throw new RuntimeException("This instance of "
                     + interfaceClazz + " class, cannot be created, because "

src/main/java/mate.academy/service/impl/ProductServiceImpl.java

@@ -12,16 +12,16 @@
 @Component
 public class ProductServiceImpl implements ProductService {
     @Inject
-    private ProductParser productParser;
+    private ProductParser txtProductParser;
 
     @Inject
-    private FileReaderService fileReaderService;
+    private FileReaderService txtFileReaderService;
 
     @Override
     public List<Product> getAllFromFile(String filePath) {
-        return fileReaderService.readFile(filePath)
+        return txtFileReaderService.readFile(filePath)
                 .stream()
-                .map(productParser::parse)
+                .map(txtProductParser::parse)
                 .collect(Collectors.toList());
     }
 }