pentaho/pentaho-kettle · error · JsonInputException

JsonInputException(ke)

Error message

JsonInputException(ke)

What it means

JsonInputException wrapping a KettleException raised while JsonInput.parseNextInputToRowSet() hands the input stream to data.reader.parse(input). The JSON reader (e.g. FastJsonReader via Json parser) failed to parse or process the stream, so the step aborts the transform after logging the underlying error.

Solutions

  1. Open the source file/URL and validate it parses as JSON (e.g. with jq or a JSON linter); fix the malformed input.
  2. Check the step log line written by logInputError for the root cause (parse error offset, IO error) and fix accordingly.
  3. If the source is a URL, verify it returns 200 with content-type application/json and is reachable from the Pentaho server host.
  4. Verify the encoding setting in the step matches the file's actual charset.
  5. If transient I/O, re-run; otherwise fix permissions on the source file.

Example fix

// before: reading a file that is not valid JSON
// after: pre-validate outside the transformation
String raw = new String(Files.readAllBytes(Paths.get(path)), StandardCharsets.UTF_8);
new JSONParser().parse(raw); // throws early with a clear position if invalid
Defensive patterns

Strategy: validation

Validate before calling

// validate JSON before running the transformation
byte[] raw = Files.readAllBytes(Paths.get(path));
if (raw.length == 0) throw new IllegalStateException("Empty JSON file: " + path);
new JSONParser().parse(new String(raw, StandardCharsets.UTF_8));

Try / catch

try { runTransformation(); }
catch (KettleException e) {
  if (e.getCause() instanceof JsonInputException) { logParseFailure(e); moveToErrorFolder(file); }
  else throw e;
}

Prevention

When it happens

Trigger: getOneOutputRow -> parseNextInputToRowSet: data.reader.parse(input) throws KettleException. Concretely: malformed JSON in a file/URL, unreadable or closed stream, or a nested KettleException from readInput (e.g. parse context null).

Common situations: Pointing the step at a truncated or non-JSON file; a URL field returning an HTML error page instead of JSON; encoding mismatch (file not in expected JSON charset); source file removed or locked between file-listing and read.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/8e24dcac65e752e9. Report an issue: GitHub.

Appendix: source

Thrown at plugins/json/core/src/main/java/org/pentaho/di/trans/steps/jsoninput/JsonInput.java:256

  @Override
  protected void fillFileAdditionalFields( JsonInputData data, FileObject file ) throws FileSystemException {
    super.fillFileAdditionalFields( data, file );
    data.filename = KettleVFS.getFilename( file );
    data.filenr++;
    if ( log.isDetailed() ) {
      logDetailed( BaseMessages.getString( PKG, "JsonInput.Log.OpeningFile", file.toString() ) );
    }
    addFileToResultFilesname( file );
  }

  private void parseNextInputToRowSet( InputStream input ) throws KettleException {
    try {
      data.readerRowSet = data.reader.parse( input );
      input.close();
    } catch ( KettleException ke ) {
      logInputError( ke );
      throw new JsonInputException( ke );
    } catch ( Exception e ) {
      logInputError( e );
      throw new JsonInputException( e );
    }
  }

  private void logInputError( KettleException e ) {
    logError( e.getLocalizedMessage(), e );
    inputError( e.getLocalizedMessage() );
  }

  private void logInputError( Exception e ) {
    String errMsg = ( !meta.isInFields() || meta.getIsAFile() )
      ? BaseMessages.getString( PKG, "JsonReader.Error.ParsingFile", data.filename )
      : BaseMessages.getString( PKG, "JsonReader.Error.ParsingString", data.readrow[ data.indexSourceField ] );
    logError( errMsg, e );
    inputError( errMsg );
  }

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