Add project-structure module: the same Boot 4.1 app laid out package-by-layer and package-by-feature, with the public surface counted and the javac boundary captured

Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5 Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5
2026-10-21 16:43:45 +00:00
parent 008211f2fa
commit ba709737de
41 changed files with 1039 additions and 0 deletions
@@ -0,0 +1,43 @@
+# The same application, two layouts (src/main/java/com/ankurm/structure)
+
+
+--- bylayer ---
+bylayer/
+  ByLayerApp.java
+  controller/
+    BookController.java
+  dto/
+    BookRequest.java
+    BookResponse.java
+  exception/
+    ApiExceptionHandler.java
+    BookNotFoundException.java
+  model/
+    Book.java
+  repository/
+    BookRepository.java
+  service/
+    BookService.java
+(9 source files)
+
+--- byfeature ---
+byfeature/
+  ByFeatureApp.java
+  book/
+    Book.java
+    BookCatalog.java
+    BookController.java
+    BookNotFoundException.java
+    BookRepository.java
+    BookRequest.java
+    BookResponse.java
+    BookService.java
+  loan/
+    Loan.java
+    LoanController.java
+    LoanRequest.java
+    LoanService.java
+  shared/
+    ApiException.java
+    ApiExceptionHandler.java
+(15 source files)
@@ -0,0 +1,32 @@
+# Top-level types per layout and whether each one is public
+
+
+--- bylayer ---
+public         bylayer.ByLayerApp
+public         bylayer.controller.BookController
+public         bylayer.dto.BookRequest
+public         bylayer.dto.BookResponse
+public         bylayer.exception.ApiExceptionHandler
+public         bylayer.exception.BookNotFoundException
+public         bylayer.model.Book
+public         bylayer.repository.BookRepository
+public         bylayer.service.BookService
+9 of 9 top-level types are public
+
+--- byfeature ---
+public         byfeature.ByFeatureApp
+package-private byfeature.book.Book
+public         byfeature.book.BookCatalog
+package-private byfeature.book.BookController
+package-private byfeature.book.BookNotFoundException
+package-private byfeature.book.BookRepository
+package-private byfeature.book.BookRequest
+package-private byfeature.book.BookResponse
+package-private byfeature.book.BookService
+package-private byfeature.loan.Loan
+package-private byfeature.loan.LoanController
+package-private byfeature.loan.LoanRequest
+package-private byfeature.loan.LoanService
+public         byfeature.shared.ApiException
+package-private byfeature.shared.ApiExceptionHandler
+3 of 15 top-level types are public
@@ -0,0 +1,8 @@
+# Can code in one package reach another package's repository?
+
+
+--- by layer: controller/Shortcut.java reaches into repository/ ---
+compiled with 0 errors
+
+--- by feature: loan/Shortcut.java reaches into book/ ---
+error: com.ankurm.structure.byfeature.book.BookRepository is not public in com.ankurm.structure.byfeature.book; cannot be accessed from outside package
@@ -0,0 +1,35 @@
+# The same requests against both layouts
+
+
+--- bylayer ---
+GET /books -> 200
+    [{"id":1,"title":"Effective Java","author":"Joshua Bloch","pages":416},{"id":2,"title":"Java Concurrency in Practice","author":"Brian Goetz","pages":384}]
+GET /books/1 -> 200
+    {"id":1,"title":"Effective Java","author":"Joshua Bloch","pages":416}
+GET /books/99 -> 404
+    {"detail":"Book 99 not found","instance":"/books/99","status":404,"title":"Not Found"}
+POST /books -> 201
+    {"id":3,"title":"Clean Code","author":"Robert Martin","pages":464}
+POST /books -> 400
+    {"timestamp":"2026-10-21T16:43:19.747Z","status":400,"error":"Bad Request","path":"/books"}
+
+--- byfeature ---
+GET /books -> 200
+    [{"id":1,"title":"Effective Java","author":"Joshua Bloch","pages":416},{"id":2,"title":"Java Concurrency in Practice","author":"Brian Goetz","pages":384}]
+GET /books/1 -> 200
+    {"id":1,"title":"Effective Java","author":"Joshua Bloch","pages":416}
+GET /books/99 -> 404
+    {"detail":"Book 99 not found","instance":"/books/99","status":404,"title":"Not Found"}
+POST /books -> 201
+    {"id":3,"title":"Clean Code","author":"Robert Martin","pages":464}
+POST /books -> 400
+    {"timestamp":"2026-10-21T16:43:20.250Z","status":400,"error":"Bad Request","path":"/books"}
+POST /loans -> 201
+    {"id":1,"bookId":2,"bookTitle":"Java Concurrency in Practice","member":"Asha"}
+POST /loans -> 404
+    {"detail":"Book 7 not found","instance":"/loans","status":404,"title":"Not Found"}
+GET /loans -> 200
+    [{"id":1,"bookId":2,"bookTitle":"Java Concurrency in Practice","member":"Asha"}]
+
+--- comparison ---
+status codes and bodies identical for the five shared requests: true
@@ -0,0 +1,10 @@
+# The controller is found only if it is in or below the @SpringBootApplication class's package
+
+
+--- app class in scan.broken.app, controller in scan.broken.web (a sibling) ---
+GET /hello -> 404
+HelloController registered as a bean: false
+
+--- app class in scan.fixed, controller in scan.fixed.web (below it) ---
+GET /hello -> 200
+HelloController registered as a bean: true
@@ -0,0 +1,14 @@
+# A @SpringBootApplication class in the default package (no package statement)
+
+source compiled:
+    import org.springframework.boot.autoconfigure.SpringBootApplication;
+    @SpringBootApplication
+    public class DefaultPackageApp {
+    }
+
+
+--- what Spring Boot logged about the default package ---
+WARNING ** : Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package.
+
+--- result ---
+context FAILED to start: BeanDefinitionStoreException / root cause ConflictingBeanDefinitionException: Annotation-specified bean name 'bookController' for bean class [com.ankurm.structure.bylayer.controller.BookController] conflicts with existing, non-compatible bean definition of same name and class [com.ankurm.structure.byfeature.book.BookController]