feat: Migrate COBOL codebase to Spring Boot application (Phase 1 & 2)

[devin-ai-integration]

Summary

Adds a spring-boot-app/ directory containing a Java Spring Boot application that migrates the COBOL example programs. This covers Phase 1 (project skeleton) and Phase 2 (data layer migration):

• Entities: Account (JPA, from sql/sql_example.cbl WORKING-STORAGE), Customer (POJO, from merge_sort/merge_sort_test.cbl)
• Repository: AccountRepository with Spring Data query methods replacing the three COBOL SQL cursors (ACCOUNT-ALL-CUR, ACCOUNT-DISABLED-CUR, ACCOUNT-QUERY-CUR)
• Services: AccountService, SerializationService (JSON/XML via Jackson), SubProgramService (CALL BY CONTENT/REFERENCE pattern), SearchService (binary search replacing SEARCH ALL)
• Controllers: AccountController (3 GET endpoints replacing the COBOL menu), SerializationController (POST endpoints for JSON/XML serialization)
• Tests: 26 tests (repository integration with H2, service unit tests with Mockito, @WebMvcTest controller tests, search behavior tests) — all passing
• README: Full COBOL-to-Java mapping tables, API docs, build/run instructions

No existing COBOL files were modified.

Updates since last revision

• Fixed Account.enabled boolean ↔ VARCHAR('Y'/'N') mapping: Added @Convert(converter = YesNoConverter.class) using Hibernate's built-in converter so the enabled field correctly translates between Java boolean and the 'Y'/'N' strings stored in the production PostgreSQL IS_ENABLED column. Previously this would have broken at runtime against the real database.

Review & Testing Checklist for Human

• Verify YesNoConverter works against real PostgreSQL: The converter has been added, but tests run against H2 with create-drop (which creates a native boolean column). Confirm that findByEnabledFalseOrderByIdAsc() generates correct SQL (IS_ENABLED = 'N') against the actual PostgreSQL VARCHAR(1) column.
• jackson-dataformat-xml version 2.17.0 is pinned explicitly while Spring Boot 3.2.5 BOM manages Jackson at ~2.15.x. Verify no runtime conflicts between Jackson modules — safer to remove the <version> and let the BOM manage it.
• SubProgramService holds mutable state (workingStorageItem1/2) in a singleton @Service bean — this is not thread-safe under concurrent HTTP requests. Consider whether this is acceptable as a demonstration or needs scoping (@RequestScope) or synchronization.
• No .gitignore in spring-boot-app/ — target/, .classpath, .project, .settings/ were manually excluded from this commit but will reappear in git status for anyone who builds locally.
• Hardcoded DB credentials in application.properties (postgres/password) — inherited from the COBOL source, but verify this is acceptable or should use env vars/profiles.

Recommended test plan:

1. cd spring-boot-app && mvn clean test — confirm all 26 tests pass
2. Stand up a local PostgreSQL with psql -f ../sql/create_test_db.sql, run mvn spring-boot:run, and hit the three account endpoints with curl — verify the IS_ENABLED Y/N values are correctly mapped to boolean
3. Test the serialization endpoints (POST /api/serialize/json and /xml) with the curl examples in the README

Notes

• SearchService and SubProgramService are standalone service beans with no REST endpoints wired to them — they exist as pattern demonstrations per the migration plan
• No global error handling (@ControllerAdvice) yet — JsonProcessingException from the serialization controller will surface as a raw 500

Link to Devin session: https://app.devin.ai/sessions/ad38878f26b640d2a8fa48bc3f5321f7
Requested by: @jerryoliphant-cog

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[devin-ai-integration]

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 5 additional findings in Devin Review.

[devin-ai-integration]

🔴 Boolean field enabled is incompatible with VARCHAR(1) 'Y'/'N' column in production database

The Account.enabled field is mapped as a Java boolean (model/Account.java:54), but the production database schema defines is_enabled as VARCHAR(1) storing 'Y' or 'N' (schema.sql:15), and the existing seed data in sql/create_test_db.sql:23-53 uses those string values. Hibernate does not automatically convert between 'Y'/'N' strings and Java boolean — there is no @Convert or AttributeConverter registered anywhere in the project. This causes two failures at runtime against the production PostgreSQL database: (1) reading existing rows with 'Y'/'N' values will fail to deserialize into boolean, and (2) derived query methods like findByEnabledFalseOrderByIdAsc() will generate SQL comparing the VARCHAR column to a boolean literal rather than 'N'. Tests pass because application-test.properties uses ddl-auto=create-drop, which creates the column as a native BOOLEAN from the entity definition, bypassing the schema.sql entirely.

Fix options

Either add a JPA AttributeConverter to convert between 'Y'/'N' and boolean, e.g.:

@Convert(converter = YesNoConverter.class)
@Column(name = "IS_ENABLED", nullable = false)
private boolean enabled;

Or change the database schema to use a native BOOLEAN column and migrate existing data.

Prompt for agents

In spring-boot-app/src/main/java/com/cobolmigration/model/Account.java, the `enabled` field (lines 53-54) is a Java `boolean` mapped to a VARCHAR(1) column that stores 'Y'/'N'. Hibernate cannot automatically convert between these types.

Fix by adding a Hibernate @Convert annotation with a built-in or custom converter. The simplest approach with Hibernate 6 (used in Spring Boot 3.x) is:

1. Add `import org.hibernate.type.YesNoConverter;` and `import jakarta.persistence.Convert;` to Account.java
2. Change the field annotation to:
   @Convert(converter = YesNoConverter.class)
   @Column(name = "IS_ENABLED", nullable = false)
   private boolean enabled;

Alternatively, create a custom AttributeConverter<Boolean, String> that maps true->'Y' and false->'N', and apply it with @Convert.

Also update spring-boot-app/src/main/resources/schema.sql line 15 to be consistent - either keep VARCHAR(1) and use the converter, or change the column to BOOLEAN and update the seed data.

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[devin-ai-integration]

Fixed in 5f68f00 — added @Convert(converter = YesNoConverter.class) using Hibernate's built-in converter to properly translate between Java boolean and the VARCHAR(1) 'Y'/'N' values in the production database. All 26 tests still pass.