HMCL-dev/HMCL · error · JsonParseException

IdDownloadInfo id can not be null

Error message

IdDownloadInfo id can not be null

What it means

IdDownloadInfo.validate() rejects a download-info entry whose id field is blank/null when a JSON version manifest is parsed. This library throws it because the id is the key used to build download URLs; without it the artifact cannot be located.

Solutions

1. Check the JSON source and fill in the missing id field for the affected entry
2. Re-download a pristine version JSON from the official manifest URL instead of a corrupted local copy
3. Fix the third-party tool that generated the partial download metadata
4. Wrap parsing in error handling and skip/re-fetch the offending entry

Example fix

// before
{"name": "something.jar", "url": "https://..."}
// after
{"id": "something", "name": "something.jar", "url": "https://..."}

if (downloadInfo == null || downloadInfo.getId() == null || downloadInfo.getId().isBlank()) {
    throw new IllegalArgumentException("entry must have a non-blank id before parsing");
}

static boolean hasId(JsonObject obj) {
    return obj.has("id") && obj.get("id").isJsonPrimitive() && !obj.get("id").getAsString().isBlank();
}

try {
    version.validate();
} catch (JsonParseException e) {
    if (e.getMessage().contains("id can not be null")) {
        // re-fetch or repair the version JSON
    } else throw e;
}

When it happens

Trigger: Deserializing a version/library asset JSON where a download object has no 'id' member or an empty-string id, then calling validate() as part of the version parsing pipeline.

Common situations: Hand-edited or truncated Minecraft version JSON, third-party launcher configs with incomplete library metadata, upstream version manifests changed or pruned.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• accountID is missing
• GameRemoteVersions.versions cannot be null
• LoggingInfo.argument is empty.
• LoggingInfo.type is empty.
• authlib-injectors.json -> urls cannot be null.

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/88b28638c37492ed. Report an issue: GitHub.

Appendix: source

Thrown at HMCLCore/src/main/java/org/jackhuang/hmcl/game/IdDownloadInfo.java:62

    public IdDownloadInfo(String id, String url, String sha1) {
        this(id, url, sha1, 0);
    }

    public IdDownloadInfo(String id, String url, String sha1, int size) {
        super(url, sha1, size);
        this.id = id;
    }

    public String getId() {
        return id;
    }

    @Override
    public void validate() throws JsonParseException, TolerableValidationException {
        super.validate();

        if (StringUtils.isBlank(id))
            throw new JsonParseException("IdDownloadInfo id can not be null");
    }

}

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