apache/flink · error · IllegalArgumentException

File path cannot be null.

Error message

File path cannot be null.

What it means

FileInputFormat.setFilePath(String) rejects a null path immediately with IllegalArgumentException. An empty string is tolerated (treated as a placeholder Path, a legacy workaround for the job-submission preview graph), but null is not, because the format must resolve a concrete filesystem location.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/io/FileInputFormat.java:255

    // --------------------------------------------------------------------------------------------
    //  Getters/setters for the configurable parameters
    // --------------------------------------------------------------------------------------------

    /**
     * Returns the paths of all files to be read by the FileInputFormat.
     *
     * @return The list of all paths to read.
     */
    public Path[] getFilePaths() {
        if (this.filePaths == null) {
            return new Path[0];
        }
        return this.filePaths;
    }

    public void setFilePath(String filePath) {
        if (filePath == null) {
            throw new IllegalArgumentException("File path cannot be null.");
        }

        // TODO The job-submission web interface passes empty args (and thus empty
        // paths) to compute the preview graph. The following is a workaround for
        // this situation and we should fix this.

        // comment (Stephan Ewen) this should be no longer relevant with the current Java/Scala
        // APIs.
        if (filePath.isEmpty()) {
            setFilePath(new Path());
            return;
        }

        try {
            this.setFilePath(new Path(filePath));
        } catch (RuntimeException rex) {
            throw new RuntimeException(
                    "Could not create a valid URI from the given file path name: "

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Provide a non-null file path string, e.g. format.setFilePath("hdfs:///data/input").
2. Validate the path is non-null before calling setFilePath.
3. Use the Path overload (setFilePath(Path)) if you already have a Path object.

Example fix

// before
String path = config.get("inputPath"); // null
format.setFilePath(path); // throws

// after
String path = checkNotNull(config.get("inputPath"), "inputPath must be set");
format.setFilePath(path);

String path = Preconditions.checkNotNull(configuredPath, "file path must be set");
format.setFilePath(path);

When it happens

Trigger: Calling format.setFilePath((String) null); passing a variable that was never assigned; reading a path from configuration that returned null and forwarding it directly.

Common situations: Building an input format programmatically from a config map where the path key is missing; copy-paste where the path variable name is misspelled/unset; refactoring that leaves a null path reference.

Related errors

• File path must not be null.
• At least one file path must be specified.
• The block size parameter must be set and larger than 0.
• Delimiter must not be null
• Line length limit must be at least 1.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/7cf49a8b5cf55e7f. Report an issue: GitHub.