How to generate sitemap xml in drupal 8 ?

Simple way to generate XML for sitemap in Drupal 8, we have 'Simple sitemap' and 'XML sitemap' modules but if we want  to add some custom code or want customization in XML, so we have simple code for generate custom XML, please follow the given process and example.

Steps:

1. Create custom module and controller file and render the below given class in file header.
   use Drupal\Core\Controller\ControllerBase;
   use Drupal\node\Entity\Node;
   use Symfony\Component\HttpFoundation\Response;
   
   
2. Write the code in controller function:
   $rows .= '<?xml version="1.0" encoding="UTF-8" ?>';
   
   //open the urlset..
   $rows .= '<urlset xmlns="http://www.google.com/schemas/sitemap/0.84"
                               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                               xsi:schemaLocation="http://www.google.com/schemas/sitemap/0.84
                               http://www.google.com/schemas/sitemap/0.84/sitemap.xsd">';
   
   If you want to add COVEO elements in XML then we have to use below given code also:
   
    $rows .= '<urlset xmlns="http://www.google.com/schemas/sitemap/0.84"   
                                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                                xsi:schemaLocation="http://www.google.com/schemas/sitemap/0.84
                                http://www.google.com/schemas/sitemap/0.84/sitemap.xsd"
                                xmlns:coveo="http://www.coveo.com/schemas/metadata">';
   
   
3. After that create the xml code with elements:
   $rows.='<url>
                <loc>'.$base_url.''.$alias.'</loc>
                <lastmod>'.$last_modified.'</lastmod>
                <changefreq>daily</changefreq>
                <priority>0.5</priority>
                <coveo:metadata>
                        <md_contenttype>'.$res_content_type.'</md_contenttype>                         
                        <md_pagetype>'.$pagetype.'</md_pagetype>
                </coveo:metadata>
                </url>';
   
   $rows .='</urlset>'; //close the urlset..
   
   
4. After that last final code for render XML:
        $response = new Response();
        $response->headers->set('Content-Type', 'text/xml'); //add content type = text/xml header.. 
        $response->setContent($rows); // pass the $row as array or xml print value..
        return $response; //return reponse with xml format without any styling..
   
   So with the help of this simple code we can create custom XML in drupal 8.

Note: If have any suggestions or issue regarding 'How to generate sitemap xml in drupal 8 ?' then you can ask by comments. 

How to alter or add custom url links in simple sitemap in drupal 8?

 It is very simple method, we have 2 options in Drupal 8.

https://www.drupal.org/project/simple_sitemap

1. we can add by config page of module like (//localhost//admin/config/search/simplesitemap/custom). There add custom links with priority with change frequency.

2. we can use alter method with simple steps::

a. Create any custom module or write code in any existing custom module.

b. go to custom_module.module file or create new if not exist.

c. write code line with below given example:

Example:

First render class library in file header.

use Drupal\simple_sitemap\Simplesitemap;

/**

 * Use this hook to add arbitrary links to the sitemap.

 *

 * @param array &$arbitrary_links

 */

function finder_simple_sitemap_arbitrary_links_alter(&$arbitrary_links) {

  // Add an arbitrary link.

  $arbitrary_links = array([

    'url' => 'https://localhost/applications',

    'priority' => '0.9',

    'lastmod' => '2020-05-25T14:40:30+02:00',

    'changefreq' => 'daily',

],

[

'url' => 'https://localhost/products',

    'priority' => '0.7',

    'lastmod' => '2020-07-15T13:40:30+02:00',

    'changefreq' => 'daily',

    ],

);

}

Note: We can't add date(lastmod) in custom links by admin, so we have to use alter code for add dates(lastmod) in custom create links.

Note: If have any suggestions or issue regarding 'How to alter or add custom url links in simple sitemap in drupal 8?' then you can ask by comments.