[英]parsing large XML using SAX in java
我試圖解析堆棧溢出數據轉儲,其中一個表稱為posts.xml,其中有大約1000萬個條目。 樣本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="<p>Now that the Engineer update has come, there will be lots of Engineers building up everywhere. How should this best be handled?</p>
" 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="<strategy><team-fortress-2><tactics>" AnswerCount="5" CommentCount="7" />
<row Id="2" PostTypeId="1" AcceptedAnswerId="184" CreationDate="2010-07-07T19:07:58.427" Score="5" ViewCount="469" Body="<p>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.</p>

<p>I would in particular like this to built remote bases in 1v1</p>
" 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="<starcraft-2><how-to><protoss>" AnswerCount="3" CommentCount="2" />
<row Id="3" PostTypeId="1" AcceptedAnswerId="56" CreationDate="2010-07-07T19:09:46.317" Score="7" ViewCount="356" Body="<p>Steam won't let me have two instances running with the same user logged in.</p>

<p>Does that mean I cannot run a dedicated server on a PC (for example, for Left 4 Dead 2) <em>and</em> play from another machine?</p>

<p>Is there a way to run the dedicated server without running steam? Is there a configuration option I'm missing?</p>
" OwnerUserId="14" LastActivityDate="2010-07-07T19:27:04.777" Title="How can I run a dedicated server from steam?" Tags="<steam><left-4-dead-2><dedicated-server><account>" AnswerCount="1" />
<row Id="4" PostTypeId="1" AcceptedAnswerId="14" CreationDate="2010-07-07T19:11:05.640" Score="10" ViewCount="201" Body="<p>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?</p>
" 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="<monkey-island><adventure>" AnswerCount="3" CommentCount="2" />
我想解析此xml,但僅加載xml的某些屬性,例如ID,PostTypeId,AcceptedAnswerId和其他2個屬性。 SAX中是否有辦法只加載這些屬性? 如果有的話怎么辦? 我對SAX還是很陌生,因此一些指導會有所幫助。
否則,加載整個程序只會很慢,而且某些屬性也不會被使用,因此毫無用處。
另一個問題是,是否有可能跳到ID為X的特定行? 如果可能的話,我該怎么做?
“ StartElement” Sax事件允許處理單個XML ELement。
在Java代碼中,您必須實現此方法
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
}
}
對於每個元素,您都可以訪問:
有關特定細節,請參見ContentHandler實現。
再見
更新:改進了以前的代碼段。
與我已經在這里回答的方法幾乎相同。
向下滾動到org.xml.sax Implementation
部分。 您只需要一個自定義處理程序。
SAX不會“加載”元素。 它會通知您的應用程序每個元素的開始和結束,並且完全由您的應用程序決定它需要注意哪些元素。
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