XML-SAX

XML解析技术常用的就是DOM和SAX，DOM(Document Object Model)即文档对象模型，将xml文件整体解析为内存中的特定数据结构，然后再对该内存中的数据机构进行操作（增删改查），SAX(Simple API for XML)即简单XML API，以流的方式读取xml文档，并以事件驱动来处理节点，其只能查询，无法对xml进行更新操作。

DOM4J是借助SAX方式来构建DOM对象，jdk中自带的DOM（com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl）的API是w3c标准API，DOM4J则是自己独有的一套API，二者的内在实现也略有不同，jdk的DOM需要将xml全部读入内存再进行解析，DOM4J则使用SAX进行流式解析（事件驱动）。

 1  <?xml version="1.0" encoding="UTF-8"?>
 2  <DocumentElement param="value">
 3      <FirstElement>
 4          &#xb6; Some Text
 5      </FirstElement>
 6      <?some_pi some_attr="some_value"?>
 7      <SecondElement param2="something">
 8          Pre-Text <Inline>Inlined text</Inline> Post-text.
 9      </SecondElement>
10 </DocumentElement>

SAX会这样解析上面的xml文件：

XML Element start, named DocumentElement, with an attribute param equal to "value"
XML Element start, named FirstElement
XML Text node, with data equal to "¶ Some Text" (note: certain white spaces can be changed)
XML Element end, named FirstElement
Processing Instruction event, with the target some_pi and data some_attr="some_value" (the content after the target is just text; however, it is very common to imitate the syntax of XML attributes, as in this example)
XML Element start, named SecondElement, with an attribute param2 equal to "something"
XML Text node, with data equal to "Pre-Text"
XML Element start, named Inline
XML Text node, with data equal to "Inlined text"
XML Element end, named Inline
XML Text node, with data equal to "Post-text."
XML Element end, named SecondElement
XML Element end, named DocumentElement

下面就使用SAX对一个spring配置文件简单解析。

spring配置文件

1 <spring:beans xmlns:spring="http://www.springframework.org/schema/beans"
2   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
4   <spring:bean id="myBean" class="com.zyong.spring.beanfactory.MyBean"/>
5 </spring:beans>

测试方法：

1 String file = ClassLoader.getSystemResource("spring/spring-test.xml").getFile();
2 com.sun.org.apache.xerces.internal.parsers.SAXParser saxParser = new com.sun.org.apache.xerces.internal.parsers.SAXParser();
3 saxParser.setContentHandler(new MyHandler());
4 saxParser.parse(new InputSource(file));

事件处理器：

 1 private class MyHandler extends DefaultHandler {
 2 
 3   @Override
 4   public void startDocument() throws SAXException {
 5     System.out.println("start document -> parse begin");
 6   }
 7 
 8   @Override
 9   public void endDocument() throws SAXException {
10         System.out.println("end document -> parse finished");
11   }
12 
13   @Override
14   public void startElement(String uri, String localName, String qName,
15                            Attributes attributes) throws SAXException {
16     System.out.println("start element-----------");
17     System.out.println("    localName: " + localName);
18     System.out.println("    qName: " + qName);
19   }
20 
21   @Override
22   public void characters(char[] ch, int start, int length)
23           throws SAXException {
24     System.out.println("characters-----------");
25     System.out.println("    ch: " + ch);
26     System.out.println("    start: " + start);
27     System.out.println("    length: " + length);
28   }
29 
30   @Override
31   public void endElement(String uri, String localName, String qName)
32           throws SAXException {
33     System.out.println("end element-----------");
34     System.out.println("    localName: " + localName);
35     System.out.println("    qName: " + qName);
36 
37   }
38 }

输出：

start document -> parse begin
start element-----------
    localName: beans
    qName: spring:beans
characters-----------
    ch: [C@4cc77c2e
    start: 272
    length: 5
start element-----------
    localName: bean
    qName: spring:bean
end element-----------
    localName: bean
    qName: spring:bean
characters-----------
    ch: [C@4cc77c2e
    start: 348
    length: 5
start element-----------
    localName: bean
    qName: spring:bean
end element-----------
    localName: bean
    qName: spring:bean
characters-----------
    ch: [C@4cc77c2e
    start: 436
    length: 1
end element-----------
    localName: beans
    qName: spring:beans
end document -> parse finished

View Code

参考：http://blog.csdn.net/u011179993/article/details/47415603

　　http://www.cnblogs.com/mengdd/archive/2013/06/02/3114177.html