baomidou/mybatis-plus · error · IOException

Unable to create directory {}

Error message

Unable to create directory {}

What it means

FileUtils.forceMkdir throws IOException when File.mkdirs() returns false AND a re-check confirms the directory still does not exist. This means the OS refused creation: a parent is not writable, a path component is a file, permissions are missing, or (rarely) a race deleted it between the two checks.

Source

Thrown at mybatis-plus-generator/src/main/java/com/baomidou/mybatisplus/generator/util/FileUtils.java:56

     */
    public static void forceMkdir(final File directory) throws IOException {
        if (directory.exists()) {
            if (!directory.isDirectory()) {
                final String message =
                    "File "
                        + directory
                        + " exists and is "
                        + "not a directory. Unable to create directory.";
                throw new IOException(message);
            }
        } else {
            if (!directory.mkdirs()) {
                // Double-check that some other thread or process hasn't made
                // the directory in the background
                if (!directory.isDirectory()) {
                    final String message =
                        "Unable to create directory " + directory;
                    throw new IOException(message);
                }
            }
        }
    }

    /**
     * Makes any necessary but nonexistent parent directories for a given File. If the parent directory cannot be
     * created then an IOException is thrown.
     *
     * @param file file with parent to create, must not be {@code null}
     * @throws NullPointerException if the file is {@code null}
     * @throws IOException          if the parent directory cannot be created
     * @since 2.5
     */
    public static void forceMkdirParent(final File file) throws IOException {
        final File parent = file.getParentFile();
        if (parent == null) {
            return;

View on GitHub (pinned to bf67d90747)

Solutions

1. Manually run `mkdir -p <path from message>` to get the real OS error (permission denied vs file exists).
2. Choose an outputDir under a location you own (project target/, build dir) or grant write permission to the user running the generator.
3. If a path component is a file, remove/rename it (see sibling error 67).

Example fix

# before (read-only path)
globalConfig.setOutputDir("/opt/app/src-gen");

# after
globalConfig.setOutputDir(System.getProperty("user.dir") + "/build/src-gen");

File dir = new File(outputDir).getAbsoluteFile();
if (!dir.exists() && !dir.mkdirs()) {
    throw new IllegalStateException("no write permission for outputDir: " + dir
        + " (writable=" + dir.getParentFile().canWrite() + ")");
}

try {
    generator.generate();
} catch (RuntimeException e) {
    if (e.getCause() instanceof IOException io && io.getMessage().startsWith("Unable to create directory")) {
        log.error("fix permissions on output dir; message names the path");
    }
}

When it happens

Trigger: Generating into a read-only or permission-restricted outputDir (e.g. '/' or '/opt/app' as non-root), a path where some intermediate component exists as a file, or sandboxed CI containers with a read-only filesystem layer.

Common situations: Running the generator in Docker/CI where the working dir is read-only; outputDir configured from a property that resolves to a path the current user cannot create; NFS mount with root_squash denying mkdir.

Related errors

• File {} exists and is not a directory. Unable to create dire
• An exception occurred in the output file:
• Illegal directory {}
• %s 的名称转换结果为空，请检查是否配置问题
• `include` and `exclude` configurations are mutually exclusiv

AI-assisted analysis of baomidou/mybatis-plus@bf67d90747 (2026-08-14). Data as JSON: /api/errors/9fba4260975990e2. Report an issue: GitHub.