apache/flink · error · IllegalArgumentException

File path must not be null.

Error message

File path must not be null.

What it means

The Path overload of FileInputFormat.setFilePath delegates to setFilePaths(filePath) after a null check. A null Path cannot be resolved to a filesystem location, so it is rejected with IllegalArgumentException. This guards the typed entry point that the String overload (error 312) feeds into.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/io/FileInputFormat.java:285

        }

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

    /**
     * Sets a single path of a file to be read.
     *
     * @param filePath The path of the file to read.
     */
    public void setFilePath(Path filePath) {
        if (filePath == null) {
            throw new IllegalArgumentException("File path must not be null.");
        }

        setFilePaths(filePath);
    }

    /**
     * Sets multiple paths of files to be read.
     *
     * @param filePaths The paths of the files to read.
     */
    public void setFilePaths(String... filePaths) {
        Path[] paths = new Path[filePaths.length];
        for (int i = 0; i < paths.length; i++) {
            paths[i] = new Path(filePaths[i]);
        }
        setFilePaths(paths);
    }

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Construct and pass a non-null Path, e.g. format.setFilePath(new Path(uri)).
2. Validate with Preconditions.checkNotNull(path, ...) before calling setFilePath.
3. Prefer the String overload when you only have a string, so the URI-error message is clearer.

Example fix

// before
Path p = maybeResolvePath(); // null
format.setFilePath(p); // throws

// after
Path p = Preconditions.checkNotNull(maybeResolvePath(), "path must be resolved");
format.setFilePath(p);

Path p = Preconditions.checkNotNull(resolvedPath, "path must be resolved");
format.setFilePath(p);

When it happens

Trigger: Calling format.setFilePath((Path) null); passing a Path variable that was constructed from null parts or never assigned.

Common situations: Building the path conditionally and forgetting the branch that leaves it null; chaining new Path(null); refactoring that drops the assignment.

Related errors

• File path cannot 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/2bd9b479f47a0027. Report an issue: GitHub.