如何從Java中的XML文件獲取信息

Question

我試圖使用Xpath從XML文件中獲取信息。 但是我不能成功。 我試圖使用來獲取Wiki內部摘要和內容的信息（在代碼底部）：

String xpath="/*[local-name(.)='wiki']/*[local-name(.)='summary']";

但是我什么也得不到。我想我的xpath錯了嗎？ 還是因為這個CDATA？ 我完全是新手，有沒有小費？

<lfm status="ok">
<album>
<name>Believe</name>
<artist>Cher</artist>
<id>2026126</id>
<mbid>61bf0388-b8a9-48f4-81d1-7eb02706dfb0</mbid>
<url>http://www.last.fm/music/Cher/Believe</url>
<releasedate>5 Jul 2005, 00:00</releasedate>
<image size="small">http://userserve-ak.last.fm/serve/34s/88057565.png</image>
<image size="medium">http://userserve-ak.last.fm/serve/64s/88057565.png</image>
<image size="large">
http://userserve-ak.last.fm/serve/174s/88057565.png
</image>
<image size="extralarge">
http://userserve-ak.last.fm/serve/300x300/88057565.png
</image>
<image size="mega">
http://userserve-ak.last.fm/serve/_/88057565/Believe.png
</image>
<listeners>259410</listeners>
<playcount>1501557</playcount>
<tracks>
<track rank="1">
<name>Believe</name>
<duration>239</duration>
<mbid>403ceb02-581b-4c36-8814-6f2a29a3d213</mbid>
<url>http://www.last.fm/music/Cher/_/Believe</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="2">
<name>The Power</name>
<duration>233</duration>
<mbid>6b3de6b5-db70-49c9-b58d-e132a3eb1a36</mbid>
<url>http://www.last.fm/music/Cher/_/The+Power</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="3">
<name>Runaway</name>
<duration>286</duration>
<mbid>379f760d-1f29-4317-ab04-06a8218a874d</mbid>
<url>http://www.last.fm/music/Cher/_/Runaway</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="4">
<name>All or Nothing</name>
<duration>238</duration>
<mbid>a88735e6-b35c-4379-8ef7-bbd2b793ccf4</mbid>
<url>http://www.last.fm/music/Cher/_/All+or+Nothing</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="5">
<name>Strong Enough</name>
<duration>220</duration>
<mbid>26107af6-7dda-4844-85a5-8d61f24f4fc2</mbid>
<url>http://www.last.fm/music/Cher/_/Strong+Enough</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="6">
<name>Dov'è L'amore</name>
<duration>258</duration>
<mbid>58153307-25dd-4ff6-87f0-e08777e34539</mbid>
<url>
http://www.last.fm/music/Cher/_/Dov%27%C3%A8+L%27amore
</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="7">
<name>Takin' Back My Heart</name>
<duration>272</duration>
<mbid>07a38e80-ba81-494a-a61a-e8d81a40413e</mbid>
<url>
http://www.last.fm/music/Cher/_/Takin%27+Back+My+Heart
</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="8">
<name>Taxi Taxi</name>
<duration>304</duration>
<mbid>66f526c9-b135-4458-86cf-77065ce8f0aa</mbid>
<url>http://www.last.fm/music/Cher/_/Taxi+Taxi</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="9">
<name>Love Is the Groove</name>
<duration>271</duration>
<mbid>832f8f9a-95e4-476b-b108-14dec1dc84ba</mbid>
<url>http://www.last.fm/music/Cher/_/Love+Is+the+Groove</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
<track rank="10">
<name>We All Sleep Alone</name>
<duration>236</duration>
<mbid>2286a77a-644a-4c86-9d43-31c029c3625b</mbid>
<url>http://www.last.fm/music/Cher/_/We+All+Sleep+Alone</url>
<streamable fulltrack="0">0</streamable>
<artist>
<name>Cher</name>
<mbid>bfcc6d75-a6a5-4bc6-8282-47aec8531818</mbid>
<url>http://www.last.fm/music/Cher</url>
</artist>
</track>
</tracks>
<toptags>
<tag>
<name>sourabh</name>
<url>http://www.last.fm/tag/sourabh</url>
</tag>
<tag>
<name>albums</name>
<url>http://www.last.fm/tag/albums</url>
</tag>
<tag>
<name>pop</name>
<url>http://www.last.fm/tag/pop</url>
</tag>
<tag>
<name>90s</name>
<url>http://www.last.fm/tag/90s</url>
</tag>
<tag>
<name>dance</name>
<url>http://www.last.fm/tag/dance</url>
</tag>
</toptags>
<wiki>
<published>Sat, 6 Mar 2010 16:48:03 +0000</published>
<summary>
<![CDATA[
Believe is the twenty-third studio album by American singer-actress Cher, released on November 10, 1998 by Warner Bros. Records. The RIAA certified it Quadruple Platinum on December 23, 1999, recognizing four million shipments in the United States; Worldwide, the album has sold more than 20 million copies, making it the biggest-selling album of her career. In 1999 the album received three Grammy Awards nominations including &quot;Record of the Year&quot;, &quot;Best Pop Album&quot; and winning &quot;Best Dance Recording&quot; for the single &quot;Believe&quot;.
]]>
</summary>
<content>
<![CDATA[
Believe is the twenty-third studio album by American singer-actress Cher, released on November 10, 1998 by Warner Bros. Records. The RIAA certified it Quadruple Platinum on December 23, 1999, recognizing four million shipments in the United States; Worldwide, the album has sold more than 20 million copies, making it the biggest-selling album of her career. In 1999 the album received three Grammy Awards nominations including &quot;Record of the Year&quot;, &quot;Best Pop Album&quot; and winning &quot;Best Dance Recording&quot; for the single &quot;Believe&quot;.

 It was released by Warner Bros. Records at the end of 1998. The album was executive produced by Rob Dickens. Upon its debut, critical reception was generally positive. Believe became Cher's most commercially-successful release, reached number one and Top 10 all over the world. In the United States, the album was released on November 10, 1998, and reached number four on the Billboard 200 chart, where it was certified four times platinum.

 The album featured a change in Cher's music; in addition, Believe presented a vocally stronger Cher and a massive use of vocoder and Auto-Tune. In 1999, the album received 3 Grammy Awards nominations for &quot;Record of the Year&quot;, &quot;Best Pop Album&quot; and winning &quot;Best Dance Recording&quot;. Throughout 1999 and into 2000 Cher was nominated and winning many awards for the album including a Billboard Music Award for &quot;Female Vocalist of the Year&quot;, Lifelong Contribution Awards and a Star on the Walk of Fame shared with former Sonny Bono. The boost in Cher's popularity led to a very successful Do You Believe? Tour.

 The album was dedicated to Sonny Bono, Cher's former husband who died earlier that year from a skiing accident.

 Cher also recorded a cover version of &quot;Love Is in the Air&quot; during early sessions for this album. Although never officially released, the song has leaked on file sharing networks.

 Singles


 &quot;Believe&quot;
 &quot;Strong Enough&quot;
 &quot;All or Nothing&quot;
 &quot;Dov'è L'Amore&quot; User-contributed text is available under the Creative Commons By-SA License and may also be available under the GNU FDL.
]]>
</content>
</wiki>
</album>
</lfm>

和Java部分：

String urlToRead =" http://ws.audioscrobbler.com/2.0/?method=album.getinfo&api_key=1b76cd3eaf8349f06fb4e0a9e06e0760&artist=Cher&album=Believe";
URL url;
HttpURLConnection conn;
BufferedReader rd;
String line;
String result = "";
try {
    url = new URL(urlToRead);
    conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));

    while ((line = rd.readLine()) != null) {

        result += line;
    }
    rd.close();
} catch (Exception e) {
    e.printStackTrace();
}
String  out = result;
SAXReader reader = new SAXReader(false);
reader.setIncludeInternalDTDDeclarations(false);
reader.setIncludeExternalDTDDeclarations(false);
String xpath="/*[local-name(.)='wiki']/*[local-name(.)='summary']";
Document document = null;
try {
    document = reader.read(new StringReader(out));
} catch (DocumentException e) {
    e.printStackTrace();
}
List nodelist = document.selectNodes(xpath);

ArrayList outputList = new ArrayList();
ArrayList outputXmlList = new ArrayList();

String val = null;
String xmlVal = null;
for (Iterator iter = nodelist.iterator(); iter.hasNext();) {
    Node element = (Node) iter.next();
    xmlVal = element.asXML();
    val = element.getStringValue();
    if (val != null && !val.equals("")) {
        outputList.add(val);
        outputXmlList.add(xmlVal);

    }

}
System.out.println(outputList.get(0));

Answer 1

您在問題中提供的XPath：

/*[local-name(.)='wiki']/*[local-name(.)='summary']

是從文檔根節點開始的絕對路徑，因此要使其匹配，將需要wiki元素作為文檔的根元素，並以summary作為其直接子元素。 這與您提供的XML不匹配，該XML的lfm根目錄包含子album ，其中包含wiki元素。

給定您的示例XML不涉及任何名稱空間，您可以省去local-name技巧，而只需使用類似

/lfm/album/wiki/summary