What causes "File cannot be read: ${file}" in quarkusio/quarkus?

Grant read permission on the file (chmod +r) or to the JVM's user/group.

quarkusio/quarkus · error · IllegalArgumentException

File cannot be read: ${file}

Error message

File cannot be read: ${file}

What it means

FilePart requires read access to the file it will send. If the JVM process cannot read the file (permission bits or ownership deny access), the constructor throws this IllegalArgumentException before any bytes are sent.

Source

Thrown at independent-projects/resteasy-reactive/common/runtime/src/main/java/org/jboss/resteasy/reactive/FilePart.java:38

    /**
     * The number of bytes to send
     */
    public final long count;

    /**
     * Create a new partial {@link File} object.
     *
     * @param file The file to send
     * @param offset The starting byte of the file (must be >= 0)
     * @param count The number of bytes to send (must be >= 0 and offset+count <= file size)
     */
    public FilePart(File file, long offset, long count) {
        if (!file.exists())
            throw new IllegalArgumentException("File does not exist: " + file);
        if (!file.isFile())
            throw new IllegalArgumentException("File is not a regular file: " + file);
        if (!file.canRead())
            throw new IllegalArgumentException("File cannot be read: " + file);
        if (offset < 0)
            throw new IllegalArgumentException("Offset (" + offset + ") must be >= 0: " + file);
        if (count < 0)
            throw new IllegalArgumentException("Count (" + count + ") must be >= 0: " + file);
        if ((offset + count) > file.length())
            throw new IllegalArgumentException(
                    "Offset + count (" + (offset + count) + ") larger than file size (" + file.length() + "): " + file);
        this.file = file;
        this.offset = offset;
        this.count = count;
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

Grant read permission on the file (chmod +r) or to the JVM's user/group.
Have the producing process write the file with world/group-readable permissions.
Run the application under a user that owns or can read the file.
Copy the file to an application-writable, readable location first.

Example fix

// before
new FilePart(new File("/secure/data.bin"), 0, len); // 0600 root-owned
// after
Process p = Runtime.getRuntime().exec(new String[]{"chmod", "g+r", "/secure/data.bin"});
p.waitFor();
new FilePart(new File("/secure/data.bin"), 0, len);

Defensive patterns

Strategy: validation

Validate before calling

Path p = file.toPath();
if (!Files.isReadable(p)) throw new IllegalStateException("Not readable by JVM user: " + p);

Type guard

static boolean isReadableFile(File f) {
    return f.canRead();
}

Try / catch

try {
    return new FilePart(file, offset, count);
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("File cannot be read")) {
        throw new IllegalStateException("Permission denied reading " + file.getAbsolutePath() + ", running as user " + System.getProperty("user.name"), e);
    }
    throw e;
}

Prevention

Check Files.isReadable before constructing parts
Ensure container/non-root users have read access to upload directories
Set permissive-enough umask in the producing process
Test file access under the same user the app runs as

When it happens

Trigger: new FilePart(file, offset, count) where file.canRead() returns false.

Common situations: Container/non-root user lacking read permission on an uploaded file written by another user; files created with restrictive umask (0600) by a different process; running in a hardened environment with SELinux/AppArmor restrictions.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/ab1f04f99b67938a. Report an issue: GitHub.