如何读取XML文件的所有子节点?

I've got this file:

我有这个文件:

<?xml version='1.0' encoding='UTF-8'?>
<feed xmlns='https://www.w3.org/2005/Atom' xmlns:app='https://purl.org/atom/app#' xmlns:media='https://search.yahoo.com/mrss/' xmlns:openSearch='https://a9.com/-/spec/opensearchrss/1.0/' xmlns:gd='https://schemas.google.com/g/2005' xmlns:gml='https://www.opengis.net/gml' xmlns:yt='https://gdata.youtube.com/schemas/2007' xmlns:georss='https://www.georss.org/georss'>
    <id>https://gdata.youtube.com/feeds/api/users/snifyy/favorites</id>
    <updated>2011-09-26T16:21:40.933Z</updated>
    <category scheme='https://schemas.google.com/g/2005#kind' term='https://gdata.youtube.com/schemas/2007#video'/>
    <title type='text'>Favorites of snifyy</title>
    <logo>https://www.youtube.com/img/pic_youtubelogo_123x63.gif</logo>
    <author>
        <name>snifyy</name>
        <uri>https://gdata.youtube.com/feeds/api/users/snifyy</uri>
    </author>
    <generator version='2.1' uri='https://gdata.youtube.com'>YouTube data API</generator>
    <openSearch:totalResults>631</openSearch:totalResults>
    <openSearch:startIndex>1</openSearch:startIndex>
    <openSearch:itemsPerPage>25</openSearch:itemsPerPage>
    <entry>
        <id>https://gdata.youtube.com/feeds/api/videos/LXO-jKksQkM</id>
        <published>2011-09-23T16:15:27.000Z</published>
        <updated>2011-09-26T16:21:15.000Z</updated>
        <title type='text'>PUMPED UP KICKS|DUBSTEP</title>
        <content type='text'>DUBSTEPPIN!!! to a beast track remixed by "butch clancy"</content>
        <link rel='alternate' type='text/html' href='/go.html?url=https://www.youtube.com/watch?v=LXO-jKksQkM&amp;feature=youtube_gdata'/>
        <link rel='https://gdata.youtube.com/schemas/2007#video.responses' type='application/atom+xml' href='/go.html?url=https://gdata.youtube.com/feeds/api/videos/LXO-jKksQkM/responses'/>
        <link rel='https://gdata.youtube.com/schemas/2007#video.related' type='application/atom+xml' href='/go.html?url=https://gdata.youtube.com/feeds/api/videos/LXO-jKksQkM/related'/>
        <link rel='https://gdata.youtube.com/schemas/2007#mobile' type='text/html' href='/go.html?url=https://m.youtube.com/details?v=LXO-jKksQkM'/>
        <link rel='related' type='application/atom+xml' href='/go.html?url=https://gdata.youtube.com/feeds/api/videos/LXO-jKksQkM'/>
        <link rel='self' type='application/atom+xml' href='/go.html?url=https://gdata.youtube.com/feeds/api/users/snifyy/favorites/LXO-jKksQkM'/>
        <author>
            <name>WHZGUD2</name>
            <uri>https://gdata.youtube.com/feeds/api/users/whzgud2</uri>
        </author>
        <gd:comments>
            <gd:feedLink href='/go.html?url=https://gdata.youtube.com/feeds/api/videos/LXO-jKksQkM/comments' countHint='3738'/>
        </gd:comments>
        <media:group>
            <media:category label='Entertainment' scheme='https://gdata.youtube.com/schemas/2007/categories.cat'>Entertainment</media:category>
            <media:content url='https://www.youtube.com/v/LXO-jKksQkM?f=user_favorites&amp;app=youtube_gdata' type='application/x-shockwave-flash' medium='video' isDefault='true' expression='full' duration='327' yt:format='5'/>
            <media:content url='rtsp://v3.cache5.c.youtube.com/CioLENy73wIaIQlDQiypjL5zLRMYDSANFEgGUg51c2VyX2Zhdm9yaXRlcww=/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='327' yt:format='1'/>
            <media:content url='rtsp://v1.cache2.c.youtube.com/CioLENy73wIaIQlDQiypjL5zLRMYESARFEgGUg51c2VyX2Zhdm9yaXRlcww=/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='327' yt:format='6'/>
            <media:description type='plain'>DUBSTEPPIN!!! to a beast track remixed by "butch clancy"</media:description>
            <media:keywords>DUBSTEP, butch, clancy, bass</media:keywords>
            <media:player url='https://www.youtube.com/watch?v=LXO-jKksQkM&amp;feature=youtube_gdata_player'/>
            <media:thumbnail url='https://i.ytimg.com/vi/LXO-jKksQkM/0.jpg' height='360' width='480' time='00:02:43.500'/>
            <media:thumbnail url='https://i.ytimg.com/vi/LXO-jKksQkM/1.jpg' height='90' width='120' time='00:01:21.750'/>
            <media:thumbnail url='https://i.ytimg.com/vi/LXO-jKksQkM/2.jpg' height='90' width='120' time='00:02:43.500'/>
            <media:thumbnail url='https://i.ytimg.com/vi/LXO-jKksQkM/3.jpg' height='90' width='120' time='00:04:05.250'/>
            <media:title type='plain'>PUMPED UP KICKS|DUBSTEP</media:title>
            <yt:duration seconds='327'/>
        </media:group>
        <gd:rating average='4.96415' max='5' min='1' numRaters='24435' rel='https://schemas.google.com/g/2005#overall'/>
        <yt:statistics favoriteCount='16660' viewCount='924793'/>
    </entry>
</feed>
<?xml version='