DJ-69: Migrate CBSTM03A statement batch to Java + Spring Boot statement viewer

[devin-ai-integration]

Summary

Implements Jira DJ-69: modernizes the CardDemo statement batch (app/cbl/CBSTM03A.CBL + app/cbl/CBSTM03B.CBL) into a new Java 17 Maven module carddemo-java, plus a Spring Boot web statement viewer replacing the COBOL-generated HTML statements. Built by two parallel workstreams (batch migration + viewer) against a locked statement JSON contract, then merged and wired end-to-end.

• Contract (carddemo-java/docs/statement-contract.json + statement-contract.schema.json) — canonical statement JSON per DJ-69: {accountId, customer{firstName,lastName,addressLines[]}, cardNumber (masked), transactions[{transactionId,description,amount}], totalAmount}.
• Generator (com.carddemo.statement.generator / parser / model) — ports the 1000-MAINLINE join: iterate cardxref.txt, look up customer (custdata.txt) and account (acctdata.txt), aggregate dailytran.txt transactions per card, compute totals; parses fixed-width layouts from app/cpy/ copybooks incl. COBOL signed-overpunch zoned decimals (e.g. 0000009190} → -919.00). Run: cd carddemo-java && mvn compile exec:java → writes one statement-<accountId>.json per account into carddemo-java/output/statements/ (50 statements / 300 transactions from app/data/ASCII/).
• Viewer (com.carddemo.statement.viewer) — Spring Boot + Thymeleaf: / lists statements, /statements/{accountId} renders name, address, masked card, transaction table and total; also GET /api/statements[/{accountId}]. Reads carddemo.statements.dir (default output/statements/); Jackson fails on unknown properties so contract drift surfaces immediately. Mock fixtures used during parallel development were removed; tests use fixtures under src/test/resources/statement-fixtures/.

Verification: (cd carddemo-java && mvn test) — 13 tests pass; (cd carddemo-java && mvn package -DskipTests) passes; viewer verified in-browser against real generated statements.

Ticket vs COBOL discrepancy (ticket wins, per instructions)

5000-CREATE-STATEMENT also emits customer middle name, current balance (ACCT-CURR-BAL) and FICO score (CUST-FICO-CREDIT-SCORE), and 3 combined address lines. The DJ-69 contract intentionally omits middle name, current balance, and FICO score, so the JSON and viewer do too.

Before — COBOL-generated HTML statement layout

The COBOL batch cannot execute off-mainframe (CBSTM03A dereferences TIOT/PSA pointers; GnuCOBOL run segfaults), so the BEFORE capture reproduces the exact HTML structure emitted by 5100-WRITE-HTML-HEADER/5200-WRITE-HTML-NMADBS/6000-WRITE-TRANS, populated with the real app/data/ASCII/ sample data.

After — new web statement viewer (real generated data)

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/ceef61b01e144b39ad60fd42e2b198d7
Requested by: @HJscarr

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