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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Jackson 3: FAIL_ON_TRAILING_TOKENS default flip not compensated in main-source parsers (JSONataUtils.loadJSONFile + CLI)","articleBody":"## Summary\n\nJackson 3 flips the `FAIL_ON_TRAILING_TOKENS` deserialization default from `false` (Jackson 2) to `true`. During the migration (#430, PR #431) this leniency was restored on exactly **one** test mapper (`src/test/java/.../expressions/utils/Utils.java:83`) but was **not** restored on the main‑source parse paths, so those became stricter than under Jackson 2. Content after the first parsed value (trailing tokens / trailing typos / concatenated values) that Jackson 2 silently ignored now throws at runtime.\n\nThe core public evaluate path is unaffected (it takes a pre‑parsed `JsonNode`), which is why the test suite stayed green. The exposure is in the file/string loaders below.\n\n## Where\n\n### Main source (production / public API)\n\n- **`src/main/java/com/api/jsonata4java/JSONataUtils.java:374`** — `loadJSONFile` uses `new ObjectMapper().readValue(br, Object.class)`. This is a **public utility** used to load `.json` files. A file that loaded fine under 2.x (trailing whitespace‑separated token, two concatenated values, etc.) now throws a trailing‑token error. **Highest impact.**\n- `src/main/java/com/api/jsonata4java/Tester.java:123` — the mapper was faithfully rebuilt for `ESCAPE_NON_ASCII` but does **not** disable `FAIL_ON_TRAILING_TOKENS`. Clearest evidence the flag flip was known (fixed in test `Utils`) but applied inconsistently. CLI tool, lower impact.\n- `src/main/java/com/api/jsonata4java/TesterTimeBox.java:121` — `new ObjectMapper()` for `readTree`. CLI tool.\n- `src/main/java/com/api/jsonata4java/testerui/TesterUI.java` and `Test.java` — same pattern; demo/UI, low impact.\n\n### Test source (latent inconsistency)\n\n- `src/test/java/.../expressions/utils/Utils.java:76` (`getJson`) and `:247` (`toJson`) still use bare `new ObjectMapper()` while the sibling `mapper` field (line 83) disables `FAIL_ON_TRAILING_TOKENS`. Same file, divergent parsing. Currently latent (both helpers are unreferenced), but it undermines the \"parse identically to Jackson 2\" intent stated in the line‑83 comment.\n\n## Verified\n\n`FAIL_ON_TRAILING_TOKENS` defaults to `true` in jackson‑databind 3.2.0 (bytecode: `iconst_1` in the enum init) vs `false` in Jackson 2. Only `Utils.java:83` compensates.\n\n## Suggested fix\n\nIntroduce a single shared \"Jackson‑2‑compatible\" mapper factory (disabling `FAIL_ON_TRAILING_TOKENS`, and centralizing `ESCAPE_NON_ASCII` etc.) and route all parse sites through it — at minimum `JSONataUtils.loadJSONFile`, and the `Utils.java` `getJson`/`toJson` helpers, so parsing behavior no longer diverges by call site. This also addresses the duplicated builder configuration noted during review (identical `JsonMapper.builder()...` blocks now appear in `AgnosticTestSuite` and `Tester`).\n","author":{"url":"https://github.com/wnm3","@type":"Person","name":"wnm3"},"datePublished":"2026-07-07T16:39:51.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/435/JSONata4Java/issues/435"}