Android 解析XML文件（sax）

ruanjwei2011

android系統(tǒng)支持使用SAX、DOM或者pull讀取xml文件(建議不要使用DOM解析-它比較耗內(nèi)存)

SAX是一個解析速度快并且占用內(nèi)存少的xml解析器。它解析的時候采用事件驅(qū)動。

即它不需要解析完整個文檔，在按內(nèi)容順序解析文檔的過程中，SAX會判斷當(dāng)前讀到的字符是否合法的XML語法的某部分，

如果符合，則會調(diào)用某個回調(diào)方法——這些方法定義在ContentHandle接口中。

startDocument()

當(dāng)遇到文檔的開頭的時候，調(diào)用該方法，可以做一些預(yù)處理的工作

endDocument()

當(dāng)文檔結(jié)束的時候，調(diào)用該方法，可以做一些善后工作

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

當(dāng)讀到一個開始標(biāo)簽的時候，會觸發(fā)這個方法

參數(shù)分別為：命名空間、不帶命名空間的標(biāo)簽名、帶命名空間的標(biāo)簽名、得到的所有屬性名和相應(yīng)的值

endElement(String uri,String localName,String name)

在遇到結(jié)束標(biāo)簽的時候，調(diào)用該方法

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

這個方法來處理在xml文件中讀到的內(nèi)容，第一個參數(shù)用于存放文件的內(nèi)容，后面的兩個參數(shù)是讀到的字符串

在這個數(shù)組中的起始位置和長度，使用new String(ch,start,length)就可以獲取內(nèi)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>

解析過程觸發(fā)的事件為：

讀到的標(biāo)簽及內(nèi)容 觸發(fā)事件

{文檔開始} 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

寫了一個sax解析程序，來解析該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. }

寫了一個測試程序，來測試解析過程是否正確：

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. }

輸出結(jié)果：

id=10 name=LiMing age=25

id=20 name=XiaoZhang age=30