Class DdbClient

Fetch one component of an item by its 32-character id (defaults to view). Decodes by Content-Type: JSON components are parsed into json, while the XML / file components (edm, source-record, citation) are returned as text (plus the exact bytes). The id is trimmed and must then be exactly 32 upper-case letters and digits (normalizeItemId); anything else rejects with a DdbValidationError without a request. A part outside ITEM_PARTS (itemPartProblem) rejects with a DdbValidationError, a blank lang or a non-integer / negative rows/offset throws DdbError, both without a request, and lang outside ITEM_LANG_PARTS or rows/offset for any part but children rejects with a DdbValidationError (validateItemOptions). A JSON part whose body is not an object or array (null, empty, a scalar) or is an error document is a DdbParseError.

Search the DDB object index via the v2 Solr passthrough (GET /2/search/index/{collection}/{requestHandler}). Values use Solr syntax; the response is native Solr JSON. wt=json is always forced, and rows defaults to DEFAULT_SEARCH_ROWS (10). The parameters are checked first (non-blank query and strings, integers from 0 to 2^31 - 1, facetLimit -1 or more and only with facetFields); a bad one throws DdbError without a request. collection and requestHandler must be letters, digits, ., _ and - (not "." or ".."; pathNameProblem), or the call rejects with a DdbValidationError without a request. A 2xx body without the documented shape — not a JSON object, an error document, no response object with an integer numFound and a docs array — raises DdbParseError. Only request handlers that return Solr's standard response envelope (such as the default select) are supported; for any other the DdbParseError names the handler and that rule (there is no fallback).

The version string of the DDB backend, with surrounding whitespace (the body's trailing newline, CRs) trimmed. Public — works without a key. A 2xx body that is not one short version token ("7.5": letters, digits, ., _, +, -) — an HTML page, JSON, an empty body — is a DdbParseError, so the call works as a connectivity check.