feat: Java Spring Boot migration - project structure, domain models, services, CLI, and tests

[devin-ai-integration]

Summary

Complete migration of all COBOL example programs into a single Java Spring Boot application under java-migration/. The app uses Spring Shell for CLI interaction, Spring Data JPA + Flyway for database access, and Jackson for JSON/XML serialization.

What's included (29 files, ~2400 lines):

• 7 domain models: Account (JPA entity), Customer/PersonCustomer/CorpCustomer (REDEFINES → inheritance), CustomerRecord, StudentRecord, SerializableRecord
• 7 services: StringUtilService, SearchService, NumericConversionService, AccountService, FileMergeService, ReportService, SerializationService
• 3 Spring Shell command classes: AccountCommands, UtilityCommands, SubProgramCommands
• 1 Flyway migration (V1__create_accounts.sql) copied from existing sql/create_test_db.sql
• 4 unit test classes (52 tests, all passing) + 1 integration test class (Testcontainers, requires Docker)
• Documentation: java-migration/README.md and migration-matrix.md

Unit tests pass locally (mvn test -Dtest='!*IT'). Integration tests were not run (require Docker for Testcontainers).

Review & Testing Checklist for Human

• Verify CustomerRecord fixed-width field widths/offsets match the COBOL FD definitions in merge_sort/merge_sort_test.cbl. Incorrect widths would silently corrupt record parsing in fromFixedWidth()/toFixedWidth().
• Verify V1__create_accounts.sql is an accurate copy of sql/create_test_db.sql, and that Account.java @Column name mappings (first_name, last_name, is_enabled, create_dt, mod_dt) match the DDL column names exactly.
• Verify XML attribute handling for the enabled field in SerializableRecord / SerializationService.generateXml() — the COBOL TYPE OF ws-record-flag IS ATTRIBUTE should produce enabled="..." as an XML attribute, not an element.
• Run integration tests with Docker (mvn test or mvn verify) to confirm AccountRepositoryIT passes against a real PostgreSQL via Testcontainers.
• Missing .gitignore for java-migration/ — IDE artifacts (.classpath, .project, .settings/) and target/ are not ignored. They were manually excluded from this commit but will be easy to accidentally commit later.

Recommended test plan: Clone the branch, run cd java-migration && mvn clean verify with Docker running. Then mvn spring-boot:run with a local PostgreSQL (cobol_db_example database) and exercise the shell commands listed in the README.

Notes

• application.yml uses env-var placeholders (${DB_URL:...}, ${DB_USERNAME:...}, ${DB_PASSWORD:}) with sensible defaults for local dev.
• SubProgramCommands simulates COBOL working-storage persistence via mutable instance fields and CANCEL via field reset — a reasonable approximation but not a perfect semantic match.
• mouse/mouse_example.cbl intentionally not migrated (terminal curses demo, no business value).

Link to Devin session: https://app.devin.ai/sessions/518f2d09e8374455a2578de070f5f06e
Requested by: @jerryoliphant-cog

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring