在Java中使用SAX解析大型XML

| 我正在尝试分析堆栈溢出数据转储，其中一个表称为posts.xml，其中有大约1000万个条目。样本XML：

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<posts>
  <row Id=\"1\" PostTypeId=\"1\" AcceptedAnswerId=\"26\" CreationDate=\"2010-07-07T19:06:25.043\" Score=\"10\" ViewCount=\"1192\" Body=\"&lt;p&gt;Now that the Engineer update has come, there will be lots of Engineers building up everywhere.  How should this best be handled?&lt;/p&gt;&#xA;\" OwnerUserId=\"11\" LastEditorUserId=\"56\" LastEditorDisplayName=\"\" LastEditDate=\"2010-08-27T22:38:43.840\" LastActivityDate=\"2010-08-27T22:38:43.840\" Title=\"In Team Fortress 2, what is a good strategy to deal with lots of engineers turtling on the other team?\" Tags=\"&lt;strategy&gt;&lt;team-fortress-2&gt;&lt;tactics&gt;\" AnswerCount=\"5\" CommentCount=\"7\" />
  <row Id=\"2\" PostTypeId=\"1\" AcceptedAnswerId=\"184\" CreationDate=\"2010-07-07T19:07:58.427\" Score=\"5\" ViewCount=\"469\" Body=\"&lt;p&gt;I know I can create a Warp Gate and teleport to Pylons, but I have no idea how to make Warp Prisms or know if there\'s any other unit capable of transporting.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;I would in particular like this to built remote bases in 1v1&lt;/p&gt;&#xA;\" OwnerUserId=\"10\" LastEditorUserId=\"68\" LastEditorDisplayName=\"\" LastEditDate=\"2010-07-08T00:16:46.013\" LastActivityDate=\"2010-07-08T00:21:13.163\" Title=\"What protoss unit can transport others?\" Tags=\"&lt;starcraft-2&gt;&lt;how-to&gt;&lt;protoss&gt;\" AnswerCount=\"3\" CommentCount=\"2\" />
  <row Id=\"3\" PostTypeId=\"1\" AcceptedAnswerId=\"56\" CreationDate=\"2010-07-07T19:09:46.317\" Score=\"7\" ViewCount=\"356\" Body=\"&lt;p&gt;Steam won\'t let me have two instances running with the same user logged in.&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Does that mean I cannot run a dedicated server on a PC (for example, for Left 4 Dead 2) &lt;em&gt;and&lt;/em&gt; play from another machine?&lt;/p&gt;&#xA;&#xA;&lt;p&gt;Is there a way to run the dedicated server without running steam? Is there a configuration option I\'m missing?&lt;/p&gt;&#xA;\" OwnerUserId=\"14\" LastActivityDate=\"2010-07-07T19:27:04.777\" Title=\"How can I run a dedicated server from steam?\" Tags=\"&lt;steam&gt;&lt;left-4-dead-2&gt;&lt;dedicated-server&gt;&lt;account&gt;\" AnswerCount=\"1\" />
  <row Id=\"4\" PostTypeId=\"1\" AcceptedAnswerId=\"14\" CreationDate=\"2010-07-07T19:11:05.640\" Score=\"10\" ViewCount=\"201\" Body=\"&lt;p&gt;When I get to the insult sword-fighting stage of The Secret of Monkey Island, do I have to learn every single insult and comeback in order to beat the Sword Master?&lt;/p&gt;&#xA;\" OwnerUserId=\"17\" LastEditorUserId=\"17\" LastEditorDisplayName=\"\" LastEditDate=\"2010-07-08T21:25:04.787\" LastActivityDate=\"2010-07-08T21:25:04.787\" Title=\"Do I have to learn all of the insults and comebacks to be able to advance in The Secret of Monkey Island?\" Tags=\"&lt;monkey-island&gt;&lt;adventure&gt;\" AnswerCount=\"3\" CommentCount=\"2\" />

我想解析此xml，但仅加载xml的某些属性，例如ID，PostTypeId，AcceptedAnswerId和其他2个属性。 SAX中是否有办法只加载这些属性？如果有的话怎么办？我对SAX还是很陌生，所以一些指导会有所帮助。否则，加载整个程序只会很慢，并且某些属性将不会被使用，因此毫无用处。另一个问题是，是否有可能跳到ID为X的特定行？如果可能的话，我该怎么做？

已邀请:

4 个回复

课刊灭似

\“ StartElement \” Sax事件允许处理单个XML ELement。在Java代码中，您必须实现此方法

public void startElement(String uri, String localName,
    String qName, Attributes attributes)
    throws SAXException {

    if(\"row\".equals(localName)) {
        //this code is executed for every xml element \"row\"
        String id = attributes.getValue(\"id\");
        String PostTypeId = attributes.getValue(\"PostTypeId\");
        String AcceptedAnswerId = attributes.getValue(\"AcceptedAnswerId\");
        //others two
        // you have your att values for an \"row\" element
    }

 }

对于每个元素，您都可以访问：命名空间URI XML QName XML LocalName 属性图，您可以在此处提取两个属性... 有关特定细节，请参见ContentHandler实现。再见更新：改进了以前的代码段。