Android 解析XML文件（sax）

ruanjwei2011

android系统支持使用SAX、DOM或者pull读取xml文件(建议不要使用DOM解析-它比较耗内存)

SAX是一个解析速度快并且占用内存少的xml解析器。它解析的时候采用事件驱动。

即它不需要解析完整个文档，在按内容顺序解析文档的过程中，SAX会判断当前读到的字符是否合法的XML语法的某部分，

如果符合，则会调用某个回调方法——这些方法定义在ContentHandle接口中。

startDocument()

当遇到文档的开头的时候，调用该方法，可以做一些预处理的工作

endDocument()

当文档结束的时候，调用该方法，可以做一些善后工作

startElement(String namespaceURI,String localName,String qName,Attributes attr)

当读到一个开始标签的时候，会触发这个方法

参数分别为：命名空间、不带命名空间的标签名、带命名空间的标签名、得到的所有属性名和相应的值

endElement(String uri,String localName,String name)

在遇到结束标签的时候，调用该方法

characters(char[] ch,int start,int length)

这个方法来处理在xml文件中读到的内容，第一个参数用于存放文件的内容，后面的两个参数是读到的字符串

在这个数组中的起始位置和长度，使用new String(ch,start,length)就可以获取内容

如有以下xml文件

<?xml version="1.0" encoding="UTF-8"?> 

<persons>

<person id="10">

<name>LiMing</name>

<age>30</age>

</person>

<person id="20">

<name>XiaoZhang</name>

<age>25</age>

</person>

</persons>

解析过程触发的事件为：

读到的标签及内容 触发事件

{文档开始} startDocument()

<persons> startElement("","persons",null,"{Attributes}")

"\n\t" characters("<persons>...</persons>","12","2")

<person> startElement("","person",null,"{Attributes}")

"\n\t\t" characters("<persons>...</persons>","31","3")

<name> startElement("","name",null,"{Attributes}")

"LiMing" characters("<persons>...</persons>","40","2")

</name> endElement("","name",null)

"\n\t\t" characters("<persons>...</persons>","50","3")

<age> startElement("","age",null,"{Attributes}")

"30" characters("<persons>...</persons>","58","2")

</age> endElement("","age",null)

"\n\t" characters("<persons>...</persons>","67","2")

</person> endElement("","person",null)

"\n\t" characters("<persons>...</persons>","79","2")

<person> startElement("","person",null,"{Attributes}")

"\n\t\t" characters("<persons>...</persons>","98","3")

<name> startElement("","name",null,"{Attributes}")

"XiaoZhang" characters("<persons>...</persons>","107","3")

</name> endElement("","name",null)

"\n\t\t" characters("<persons>...</persons>","118","3")

<age> startElement("","age",null,"{Attributes}")

"25" characters("<persons>...</persons>","126","2")

</age> endElement("","age",null)

"\n\t\t" characters("<persons>...</persons>","135","2")

</person> endElement("","person",null)

"\n" characters("<persons>...</persons>","147","1")

</persons> endElement

写了一个sax解析程序，来解析该xml文件

1. import org.xml.sax.Attributes;
   
2. import org.xml.sax.SAXException;
   
3. import org.xml.sax.helpers.DefaultHandler;
   
4. 
   
5. public class StudentInfoContentHandler2 extends DefaultHandler {
   
6. 
   
7.     @Override
   
8.     public void characters(char[] ch, int start, int length) throws SAXException {
   
9.         if(person!=null) {
   
10.             String data = new String(ch, start, length);
    
11.             if("name".equals(tagName)) {
    
12.                 person.name = data;
    
13.             } else if("age".equals(tagName)) {
    
14.                 person.age = Integer.valueOf(data);
    
15.             }
    
16.         }
    
17.     }
    
18. 
    
19.     @Override
    
20.     public void endDocument() throws SAXException {
    
21.         for(Person p : personList) {
    
22.             System.out.println(p);
    
23.         }
    
24.     }
    
25. 
    
26.     @Override
    
27.     public void endElement(String uri, String localName, String qName) throws SAXException {        
    
28.         if("person".equals(qName)) {
    
29.             personList.add(person);
    
30.             person = null;            
    
31.         }
    
32.         tagName = null;
    
33.     }
    
34. 
    
35.     @Override
    
36.     public void startDocument() throws SAXException {
    
37.         personList = new ArrayList<Person>();
    
38.     }
    
39. 
    
40.     @Override
    
41.     public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
    
42.         if("person".equals(qName)) {                    
    
43.             person = new Person();
    
44.             person.id = Integer.valueOf(attributes.getValue("id"));
    
45.         } else {
    
46.             
    
47.         }
    
48.         tagName = qName;
    
49.     }
    
50.     
    
51.     List<Person> personList;
    
52.     Person person;
    
53.     String tagName;
    
54. }
    
55. 
    
56. 
    
57. class Person
    
58. {
    
59.     @Override
    
60.     public String toString() {
    
61.         return "id=" + id + " name=" + name + " age=" + age;
    
62.     }
    
63.     public int id;
    
64.     public String name;
    
65.     public int age;
    
66.     
    
67. }

写了一个测试程序，来测试解析过程是否正确：

1. import java.io.File;
   
2. import java.io.IOException;
   
3. 
   
4. import javax.xml.parsers.ParserConfigurationException;
   
5. import javax.xml.parsers.SAXParser;
   
6. import javax.xml.parsers.SAXParserFactory;
   
7. 
   
8. import org.xml.sax.SAXException;
   
9. 
   
10. 
    
11. public class SAX_XML_Parser {
    
12. 
    
13.     public static void main(String[] args) {        
14.         try {
    
15.             readXml();
    
16.         } catch (ParserConfigurationException e) {
    
17.             // TODO Auto-generated catch block
    
18.             e.printStackTrace();
    
19.         } catch (SAXException e) {
    
20.             // TODO Auto-generated catch block
    
21.             e.printStackTrace();
    
22.         } catch (IOException e) {
    
23.             // TODO Auto-generated catch block
    
24.             e.printStackTrace();
    
25.         }
    
26.     }
    
27. 
    
28.     private static void readXml() throws ParserConfigurationException, SAXException, IOException {
    
29.         File file = new File("C:/studentInfo.xml");
    
30.         SAXParserFactory spf = SAXParserFactory.newInstance();
    
31.         SAXParser saxParser = spf.newSAXParser();
    
32.         //saxParser.setProperty("http://xml.org/sax/features/namespaces", true);
    
33.         StudentInfoContentHandler2 handler = new StudentInfoContentHandler2();
    
34.         saxParser.parse(file, handler);        
    
35.     }    
    
36. }

输出结果：

id=10 name=LiMing age=25

id=20 name=XiaoZhang age=30