Add COBOL-to-Java/Spring Boot migration project (all 8 phases)

[devin-ai-integration]

Summary

Adds a new java-migration/ directory containing a complete Spring Boot 3.2.5 (Java 17) project that migrates all COBOL example programs into Java equivalents, organized across 8 phases:

Phase	Package	COBOL Source	Java Approach
1	stringutils	trim, unstring, is_numeric, numval	Static utility methods with regex
2	datastructures	redefines, search, comp_test	Sealed interfaces, records, TreeMap
3	serialization	json_generate, xml_generate	Jackson ObjectMapper / XmlMapper
4	batch	merge_sort	FileMergeService + Spring Batch config
5	database	sql_example	JPA entities, Spring Data repositories, Flyway
6	services	sub_program	@service beans modeling CALL/CANCEL semantics
7	web	accept, display, screen_size, mouse	REST controllers replacing terminal UI
8	reports	report_writer	Text/CSV report generation service

81 JUnit tests pass (unit + @DataJpaTest + @WebMvcTest). Tests use H2 in-memory DB. Per-phase README.md files document every COBOL-to-Java mapping decision.

Review & Testing Checklist for Human

• Verify COBOL behavioral fidelity for Phase 1 (StringUtils): The unstringMultipleDelimiters method and numval trailing-sign handling are the most complex translations — compare outputs against running the actual COBOL programs to ensure parity
• Verify Phase 5 Flyway migrations against real PostgreSQL: All DB tests run against H2 only. The V1__create_accounts_table.sql and V2__insert_test_data.sql migrations, plus the searchAccounts JPQL query (which uses LIKE with an empty escape '' clause), should be tested against the actual cobol_db_example database
• Review MergeSortJobConfig (Spring Batch): This config class defines a batch Job with merge/sort steps, but has no integration test — only the simpler FileMergeService path is tested. Verify the @Bean wiring is correct if you intend to use the batch job path
• Review CustomerController in-memory design: The controller instantiates CustomerSearchService directly and populates sample data in its constructor. This is demo/stub code — verify this matches your expectations for the migration
• Run mvn spring-boot:run with PostgreSQL configured and manually hit the REST endpoints (/api/accounts, /api/reports/customers) to verify end-to-end behavior

Notes

• Database credentials in application.yml use environment variable placeholders (${DB_URL}, ${DB_USERNAME}, ${DB_PASSWORD}) with localhost defaults
• The report page-break logic (Phase 8) uses hardcoded constants from COBOL (PAGE_LIMIT=66, LAST_DETAIL=42) but exact line-for-line output parity with COBOL Report Writer has not been validated
• @MockBean usage in AccountControllerTest is functional but deprecated in newer Spring Boot — low priority to migrate
• No @ControllerAdvice global exception handler is included — REST errors return Spring defaults

Link to Devin session: https://app.devin.ai/sessions/2addd7b899444abaa1fdd5537a6f7f27
Requested by: @jerryoliphant-cog

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