# General - How To - Recipes { #general-how-to-recipes }

Here are several pointers to other places in the docs, for general or frequent questions.

## Filter Data - Security { #filter-data-security }

To ensure that you don't return more data than you should, read the docs for [Tutorial - Response Model - Return Type](../tutorial/response-model.md){.internal-link target=_blank}.

## Documentation Tags - OpenAPI { #documentation-tags-openapi }

    }

    /**
     * Gets the embedded file from a file specification, trying different platform-specific variants.
     * @param fileSpec the file specification
     * @return the embedded file, or null if not found
     */
    protected PDEmbeddedFile getEmbeddedFile(final PDComplexFileSpecification fileSpec) {
        // search for the first available alternative of the embedded file
        PDEmbeddedFile embeddedFile = null;

        if (StringUtil.isBlank(slackWebhookUrls)) {
            return;
        }
        final String body = toSlackMessage(discloser);
        StreamUtil.split(slackWebhookUrls, "[,\\s]").of(stream -> stream.filter(StringUtil::isNotBlank).forEach(url -> {
            try (CurlResponse response = Curl.post(url).header("Content-Type", "application/json").body(body).execute()) {
                if (response.getHttpStatusCode() == 200) {

        });

        userBhv.selectCursor(cb -> cb.query().setGroups_Equal(group.getId()), entity -> {
            entity.setGroups(
                    stream(entity.getGroups()).get(stream -> stream.filter(s -> !s.equals(group.getId())).toArray(n -> new String[n])));
            userBhv.insertOrUpdate(entity);
        });

    }

    /**

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *

		if n == 0 && total != 0 {
			// Reached EOF, nothing more to be done.
			break
		}

		// We take care of the situation where if n == 0 and total == 0 by creating empty data and parity files.
		blocks, err = e.EncodeData(ctx, buf[:n])
		if err != nil {
			return 0, err
		}

		if err = writer.Write(ctx, blocks); err != nil {
			return 0, err
		}

		total += int64(n)
		if eof {

		}
	}
	return err
}

// Reliably retries os.RemoveAll if for some reason os.RemoveAll returns
// syscall.ENOTEMPTY (children has files).
func reliableRemoveAll(dirPath string) (err error) {
	i := 0
	for {
		// Removes all the directories and files.
		if err = RemoveAll(dirPath); err != nil {
			// Retry only for the first retryable error.
			if isSysErrNotEmpty(err) && i == 0 {
				i++
				continue

so performance impact should be minimal even if precompressed data is re-compressed.
Decompressing incompressible data has no significant performance impact.

Below is a list of common files and content-types which are typically not suitable for compression.

- Extensions

 | `gz`  | (GZIP)      |
 | `bz2` | (BZIP2)     |
 | `rar` | (WinRAR)    |
 | `zip` | (ZIP)       |

            final int depth, final String encoding) {
        // add url and filter
        final Set<String> urlSet = new HashSet<>();
        final List<UrlQueue<?>> childList = childUrlList.stream()
                .filter(d -> StringUtil.isNotBlank(d.getUrl()) && urlSet.add(d.getUrl()) && crawlerContext.getUrlFilter().match(d.getUrl()))
                .map(d -> {

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *