Java 11 migrate c-d (remaining) (iluwatar#1111)

* Moves converter pattern to Java 11

* Moves cqrs pattern to Java 11

* Moves dao pattern to Java 11

* Moves data-bus pattern to Java 11

* Moves data-locality pattern to Java 11

* Moves data-mapper pattern to Java 11

* Moves data-transfer-object pattern to Java 11

* Moves decorator pattern to Java 11

* Moves delegation pattern to Java 11

* Moves dependency-injection to Java 11

* Moves dirty-flag to Java 11

* Moves double-buffer to Java 11

* Moves double-checked-locking to Java 11

* Moves double-dispatch to Java 11

* Corrects with changes thats breaking test cases

Author: anuragagarwal561994

converter/README.md

@@ -63,20 +63,26 @@ The specialized converters inherit from this base class as follows.
 public class UserConverter extends Converter<UserDto, User> {
 
   public UserConverter() {
-    super(userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
-            userDto.getEmail()),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
-            user.getUserId()));
+    super(UserConverter::convertToEntity, UserConverter::convertToDto);
   }
+
+  private static UserDto convertToDto(User user) {
+    return new UserDto(user.getFirstName(), user.getLastName(), user.isActive(), user.getUserId());
+  }
+
+  private static User convertToEntity(UserDto dto) {
+    return new User(dto.getFirstName(), dto.getLastName(), dto.isActive(), dto.getEmail());
+  }
+
 }
 ```
 
 Now mapping between User and UserDto becomes trivial.
 
 ```java
-Converter<UserDto, User> userConverter = new UserConverter();
-UserDto dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
-User user = userConverter.convertFromDto(dtoUser);
+var userConverter = new UserConverter();
+var dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
+var user = userConverter.convertFromDto(dtoUser);
 ```
 
 ## Class diagram

converter/src/main/java/com/iluwatar/converter/App.java

@@ -49,8 +49,11 @@ public static void main(String[] args) {
     User user = userConverter.convertFromDto(dtoUser);
     LOGGER.info("Entity converted from DTO:" + user);
 
-    var users = List.of(new User("Camile", "Tough", false, "124sad"),
-        new User("Marti", "Luther", true, "42309fd"), new User("Kate", "Smith", true, "if0243"));
+    var users = List.of(
+        new User("Camile", "Tough", false, "124sad"),
+        new User("Marti", "Luther", true, "42309fd"),
+        new User("Kate", "Smith", true, "if0243")
+    );
     LOGGER.info("Domain entities:");
     users.stream().map(User::toString).forEach(LOGGER::info);
 

converter/src/main/java/com/iluwatar/converter/User.java

@@ -73,7 +73,7 @@ public boolean equals(Object o) {
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    User user = (User) o;
+    var user = (User) o;
     return isActive == user.isActive && Objects.equals(firstName, user.firstName) && Objects
         .equals(lastName, user.lastName) && Objects.equals(userId, user.userId);
   }

converter/src/main/java/com/iluwatar/converter/UserConverter.java

@@ -28,13 +28,16 @@
  */
 public class UserConverter extends Converter<UserDto, User> {
 
-  /**
-   * Constructor.
-   */
   public UserConverter() {
-    super(userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
-            userDto.getEmail()),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
-            user.getUserId()));
+    super(UserConverter::convertToEntity, UserConverter::convertToDto);
   }
+
+  private static UserDto convertToDto(User user) {
+    return new UserDto(user.getFirstName(), user.getLastName(), user.isActive(), user.getUserId());
+  }
+
+  private static User convertToEntity(UserDto dto) {
+    return new User(dto.getFirstName(), dto.getLastName(), dto.isActive(), dto.getEmail());
+  }
+
 }

converter/src/main/java/com/iluwatar/converter/UserDto.java

@@ -74,7 +74,7 @@ public boolean equals(Object o) {
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    UserDto userDto = (UserDto) o;
+    var userDto = (UserDto) o;
     return isActive == userDto.isActive && Objects.equals(firstName, userDto.firstName) && Objects
         .equals(lastName, userDto.lastName) && Objects.equals(email, userDto.email);
   }

converter/src/test/java/com/iluwatar/converter/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void testMain() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 
 }

converter/src/test/java/com/iluwatar/converter/ConverterTest.java

@@ -23,12 +23,11 @@
 
 package com.iluwatar.converter;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.List;
 import java.util.Random;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
 
 /**
  * Tests for {@link Converter}
@@ -42,8 +41,8 @@ public class ConverterTest {
    */
   @Test
   public void testConversionsStartingFromDomain() {
-    User u1 = new User("Tom", "Hanks", true, "[email protected]");
-    User u2 = userConverter.convertFromDto(userConverter.convertFromEntity(u1));
+    var u1 = new User("Tom", "Hanks", true, "[email protected]");
+    var u2 = userConverter.convertFromDto(userConverter.convertFromEntity(u1));
     assertEquals(u1, u2);
   }
 
@@ -52,37 +51,47 @@ public void testConversionsStartingFromDomain() {
    */
   @Test
   public void testConversionsStartingFromDto() {
-    UserDto u1 = new UserDto("Tom", "Hanks", true, "[email protected]");
-    UserDto u2 = userConverter.convertFromEntity(userConverter.convertFromDto(u1));
+    var u1 = new UserDto("Tom", "Hanks", true, "[email protected]");
+    var u2 = userConverter.convertFromEntity(userConverter.convertFromDto(u1));
     assertEquals(u1, u2);
   }
 
   /**
-   * Tests the custom users converter. Thanks to Java8 lambdas, converter can be easily and
-   * cleanly instantiated allowing various different conversion strategies to be implemented.
+   * Tests the custom users converter. Thanks to Java8 lambdas, converter can be easily and cleanly
+   * instantiated allowing various different conversion strategies to be implemented.
    */
   @Test
   public void testCustomConverter() {
-    Converter<UserDto, User> converter = new Converter<>(
-        userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
-        String.valueOf(new Random().nextInt())),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
-        user.getFirstName().toLowerCase() + user.getLastName().toLowerCase() + "@whatever.com"));
-    User u1 = new User("John", "Doe", false, "12324");
-    UserDto userDto = converter.convertFromEntity(u1);
+    var converter = new Converter<UserDto, User>(
+        userDto -> new User(
+            userDto.getFirstName(),
+            userDto.getLastName(),
+            userDto.isActive(),
+            String.valueOf(new Random().nextInt())
+        ),
+        user -> new UserDto(
+            user.getFirstName(),
+            user.getLastName(),
+            user.isActive(),
+            user.getFirstName().toLowerCase() + user.getLastName().toLowerCase() + "@whatever.com")
+    );
+    var u1 = new User("John", "Doe", false, "12324");
+    var userDto = converter.convertFromEntity(u1);
     assertEquals("[email protected]", userDto.getEmail());
   }
 
   /**
-   * Test whether converting a collection of Users to DTO Users and then converting them back to domain
-   * users returns an equal collection.
+   * Test whether converting a collection of Users to DTO Users and then converting them back to
+   * domain users returns an equal collection.
    */
   @Test
   public void testCollectionConversion() {
-    List<User> users = List.of(new User("Camile", "Tough", false, "124sad"),
-            new User("Marti", "Luther", true, "42309fd"),
-            new User("Kate", "Smith", true, "if0243"));
-    List<User> fromDtos = userConverter.createFromDtos(userConverter.createFromEntities(users));
+    var users = List.of(
+        new User("Camile", "Tough", false, "124sad"),
+        new User("Marti", "Luther", true, "42309fd"),
+        new User("Kate", "Smith", true, "if0243")
+    );
+    var fromDtos = userConverter.createFromDtos(userConverter.createFromEntities(users));
     assertEquals(users, fromDtos);
   }
 }

cqrs/src/main/java/com/iluwatar/cqrs/app/App.java

@@ -24,15 +24,9 @@
 package com.iluwatar.cqrs.app;
 
 import com.iluwatar.cqrs.commandes.CommandServiceImpl;
-import com.iluwatar.cqrs.commandes.ICommandService;
 import com.iluwatar.cqrs.constants.AppConstants;
-import com.iluwatar.cqrs.dto.Author;
-import com.iluwatar.cqrs.dto.Book;
-import com.iluwatar.cqrs.queries.IQueryService;
 import com.iluwatar.cqrs.queries.QueryServiceImpl;
 import com.iluwatar.cqrs.util.HibernateUtil;
-import java.math.BigInteger;
-import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -56,7 +50,7 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    ICommandService commands = new CommandServiceImpl();
+    var commands = new CommandServiceImpl();
 
     // Create Authors and Books using CommandService
     commands.authorCreated(AppConstants.E_EVANS, "Eric Evans", "[email protected]");
@@ -72,15 +66,15 @@ public static void main(String[] args) {
     commands.bookAddedToAuthor("Domain Specific Languages", 48.89, AppConstants.M_FOWLER);
     commands.authorNameUpdated(AppConstants.E_EVANS, "Eric J. Evans");
 
-    IQueryService queries = new QueryServiceImpl();
+    var queries = new QueryServiceImpl();
 
     // Query the database using QueryService
-    Author nullAuthor = queries.getAuthorByUsername("username");
-    Author evans = queries.getAuthorByUsername(AppConstants.E_EVANS);
-    BigInteger blochBooksCount = queries.getAuthorBooksCount(AppConstants.J_BLOCH);
-    BigInteger authorsCount = queries.getAuthorsCount();
-    Book dddBook = queries.getBook("Domain-Driven Design");
-    List<Book> blochBooks = queries.getAuthorBooks(AppConstants.J_BLOCH);
+    var nullAuthor = queries.getAuthorByUsername("username");
+    var evans = queries.getAuthorByUsername(AppConstants.E_EVANS);
+    var blochBooksCount = queries.getAuthorBooksCount(AppConstants.J_BLOCH);
+    var authorsCount = queries.getAuthorsCount();
+    var dddBook = queries.getBook("Domain-Driven Design");
+    var blochBooks = queries.getAuthorBooks(AppConstants.J_BLOCH);
 
     LOGGER.info("Author username : {}", nullAuthor);
     LOGGER.info("Author evans : {}", evans);

cqrs/src/main/java/com/iluwatar/cqrs/commandes/CommandServiceImpl.java

@@ -26,8 +26,6 @@
 import com.iluwatar.cqrs.domain.model.Author;
 import com.iluwatar.cqrs.domain.model.Book;
 import com.iluwatar.cqrs.util.HibernateUtil;
-import org.hibernate.Query;
-import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 
 /**
@@ -39,9 +37,9 @@ public class CommandServiceImpl implements ICommandService {
   private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
 
   private Author getAuthorByUsername(String username) {
-    Author author = null;
-    try (Session session = sessionFactory.openSession()) {
-      Query query = session.createQuery("from Author where username=:username");
+    Author author;
+    try (var session = sessionFactory.openSession()) {
+      var query = session.createQuery("from Author where username=:username");
       query.setParameter("username", username);
       author = (Author) query.uniqueResult();
     }
@@ -53,9 +51,9 @@ private Author getAuthorByUsername(String username) {
   }
 
   private Book getBookByTitle(String title) {
-    Book book = null;
-    try (Session session = sessionFactory.openSession()) {
-      Query query = session.createQuery("from Book where title=:title");
+    Book book;
+    try (var session = sessionFactory.openSession()) {
+      var query = session.createQuery("from Book where title=:title");
       query.setParameter("title", title);
       book = (Book) query.uniqueResult();
     }
@@ -68,8 +66,8 @@ private Book getBookByTitle(String title) {
 
   @Override
   public void authorCreated(String username, String name, String email) {
-    Author author = new Author(username, name, email);
-    try (Session session = sessionFactory.openSession()) {
+    var author = new Author(username, name, email);
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.save(author);
       session.getTransaction().commit();
@@ -78,9 +76,9 @@ public void authorCreated(String username, String name, String email) {
 
   @Override
   public void bookAddedToAuthor(String title, double price, String username) {
-    Author author = getAuthorByUsername(username);
-    Book book = new Book(title, price, author);
-    try (Session session = sessionFactory.openSession()) {
+    var author = getAuthorByUsername(username);
+    var book = new Book(title, price, author);
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.save(book);
       session.getTransaction().commit();
@@ -89,9 +87,9 @@ public void bookAddedToAuthor(String title, double price, String username) {
 
   @Override
   public void authorNameUpdated(String username, String name) {
-    Author author = getAuthorByUsername(username);
+    var author = getAuthorByUsername(username);
     author.setName(name);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -100,9 +98,9 @@ public void authorNameUpdated(String username, String name) {
 
   @Override
   public void authorUsernameUpdated(String oldUsername, String newUsername) {
-    Author author = getAuthorByUsername(oldUsername);
+    var author = getAuthorByUsername(oldUsername);
     author.setUsername(newUsername);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -111,9 +109,9 @@ public void authorUsernameUpdated(String oldUsername, String newUsername) {
 
   @Override
   public void authorEmailUpdated(String username, String email) {
-    Author author = getAuthorByUsername(username);
+    var author = getAuthorByUsername(username);
     author.setEmail(email);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -122,9 +120,9 @@ public void authorEmailUpdated(String username, String email) {
 
   @Override
   public void bookTitleUpdated(String oldTitle, String newTitle) {
-    Book book = getBookByTitle(oldTitle);
+    var book = getBookByTitle(oldTitle);
     book.setTitle(newTitle);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(book);
       session.getTransaction().commit();
@@ -133,9 +131,9 @@ public void bookTitleUpdated(String oldTitle, String newTitle) {
 
   @Override
   public void bookPriceUpdated(String title, double price) {
-    Book book = getBookByTitle(title);
+    var book = getBookByTitle(title);
     book.setPrice(price);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(book);
       session.getTransaction().commit();

cqrs/src/main/java/com/iluwatar/cqrs/dto/Author.java

@@ -80,7 +80,7 @@ public boolean equals(Object obj) {
     if (!(obj instanceof Author)) {
       return false;
     }
-    Author other = (Author) obj;
+    var other = (Author) obj;
     return username.equals(other.getUsername()) && email.equals(other.getEmail()) && name
         .equals(other.getName());
 

cqrs/src/main/java/com/iluwatar/cqrs/dto/Book.java

@@ -73,7 +73,7 @@ public boolean equals(Object obj) {
     if (!(obj instanceof Book)) {
       return false;
     }
-    Book book = (Book) obj;
+    var book = (Book) obj;
     return title.equals(book.getTitle()) && price == book.getPrice();
   }