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AI_CONTEXT.md

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+# AI Context: Dynamic Query & Low-Code Engine
+
+## 1. Project Overview
+This project explores two distinct approaches for building a "Low-Code" style backend that supports dynamic field selection, complex filtering, and deep graph traversal without writing boilerplate code.
+
+## 2. Core Architectures
+
+### A. Hibernate/JPA Strategy (Runtime Dynamic)
+*   **Goal**: Fully dynamic query construction at runtime.
+*   **Key Components**:
+    *   `BaseRepository<T, ID>`: Extends `JpaRepository` & `JpaSpecificationExecutor`.
+    *   `BaseController<T>`: Provides generic `/list` endpoint.
+    *   `GenericSpecification`: Converts Map params to JPA Predicates.
+        *   Supports exact match (default).
+        *   Supports LIKE match via wildcard `*` (e.g., `name=John*`).
+    *   `Squiggly`: Used for dynamic JSON field projection (Graph-trimming) *after* DB fetch.
+*   **Pros**: Zero code generation, extremely flexible, standard JPA ecosystem.
+*   **Cons**: "N+1" issues if not careful (Entity Graph needed for optimization), limited by JPA's performance on complex joins.
+
+### B. MyBatis XML Generation Strategy (Compile/Runtime Generation)
+*   **Goal**: Generate optimized, static-like SQL/XML artifacts for high performance and complex mapping.
+*   **Key Components**:
+    *   `MyBatisGeneratorUtils`: The core engine.
+*   **Mechanism**:
+    1.  **ResultMap Generation**:
+        *   Generates standard `<resultMap>` for each involved Entity.
+        *   Uses `columnPrefix` (e.g., `author$`, `books$`) to link nested associations/collections recursively.
+        *   This allows infinite recursion (Book -> Author -> Book) using the same set of ResultMaps.
+    2.  **SQL Generation**:
+        *   Builds a Join Tree based on requested fields (e.g., `["title", "author.books.title"]`).
+        *   Generates `LEFT JOIN`s automatically.
+        *   **Smart Alias Strategy**:
+            *   Table Alias: Full path (e.g., `book$author$books`) to avoid collisions.
+            *   Column Alias: `path$ColumnName` (e.g., `author$books$publish_month`).
+            *   **Crucial**: The last part of the alias MUST be the DB Column Name (not Java Field Name) to match `<result column="...">` during prefix stripping.
+    3.  **One-To-Many Handling**:
+        *   Detects `@OneToMany(mappedBy=...)` to generate correct `ON parent.id = child.parent_id` join condition.
+        *   **Forced ID Projection**: Automatically selects `id` columns for all nodes to ensure correct MyBatis collection folding.
+*   **Pros**: High performance (single SQL), solves N+1, precise column selection.
+*   **Cons**: Requires generation step (or runtime string manipulation), more complex engine logic.
+
+## 3. Key Files & Locations
+*   `com.example.demo.util.MyBatisGeneratorUtils`: The "Brain" of the MyBatis strategy.
+*   `com.example.demo.repository.GenericSpecification`: The "Brain" of the JPA strategy.
+*   `com.example.demo.controller.BaseController`: The generic entry point.
+
+## 4. Current Status
+*   JPA Strategy: Fully functional. Read operations support wildcard search and dynamic projection. Write operations support cascading creation and deep-merge patching.
+*   MyBatis Strategy: Engine is complete and tested (`MyBatisGeneratorUtilsTest`). Capable of generating full valid XML with recursive mappings and List support. Integration into Controller is the next logical step.