SAX解析XML

本帖最后由 JenMinZhang 于 2012-11-6 13:47 编辑


       1.  SAX解析XML简单介绍 ：SAX是 Simple API for XML(XML 简单应用程序接口），是一个公共的基于事件的XML文档解析标准。它以事件作为解析XML 文件的模式，   将 XML 文件转化成一系列的事件，由不同的事件处理器来决定如何处理。
          SAX是一个解析速度快并且占用内存少的xml解析器，非常适合android等移动设备，SAX解析XML文件采用的是事件驱动，也就是说，它并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会判断当前读取到的字符是否合法xml语法中的某部分，如果符合就会触发事件。
                                                                                             解析流程：
    
 




2.使用SAX解析网络XML：
(1)准备工作：
寻找要解析的XML文件网络路径，可以使用网络路径为：
http://www.w3school.com.cn/example/xmle/plant_catalog.xml  
(2)XML文件对应Model：

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import java.io.Serializable;   public class Plant implements Serializable {          /**           *           */          private static final long serialVersionUID = 1L;                    private String common= "" ;          private String botanical= "" ;          private String  zone= "" ;          private String price= "" ;          private String availability= "" ;                    public String getCommon() {                  return common;          }          public void setCommon(String common) {                  this .common = common;          }          public String getBotanical() {                  return botanical;          }          public void setBotanical(String botanical) {                  this .botanical = botanical;          }          public String getZone() {                  return zone;          }          public void setZone(String zone) {                  this .zone = zone;          }          public String getPrice() {                  return price;          }          public void setPrice(String price) {                  this .price = price;          }          public String getAvailability() {                  return availability;          }          public void setAvailability(String availability) {                  this .availability = availability;          }     }

(3)助手类代码：
a.引入包 ：

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import java.io.InputStream; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.net.HttpURLConnection; import java.net.URL; import java.sql.Date; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.List;   import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory;   import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler;

b.助手类代码：

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/**   * 助手类 传递一个网络XML地址和一个对象实体类实例对象即可解析XML内容   *   * @author JenMinZhang   */ public class SAXParserContentHandler extends DefaultHandler {          private Object javaBean = null ;          private String tag; // 标签名称          List<Object> list = null ;            /**           * 用 SAX 解析xml文件           *           * @param strUrl           *            网络xml地址           * @param javaBean           *            实体类对象           * @return List 返回实体类的一个list集合           * @throws Exception           */          public List<Object> parseReadXml(String strUrl, Object javaBean)                          throws Exception {                  this .javaBean = javaBean;                  // 要从网络上获取xml，要定义一个URL类对象                  URL url = new URL(strUrl);                  // 打开连接,。会返回HttpsURLConnection 对象                  HttpURLConnection httpsURLConnection = (HttpURLConnection) url                                  .openConnection();                  // 现在是使用HTTP协议请求服务器的数据                  // 所以要设置请求方式                  httpsURLConnection.setRequestMethod( "GET" );                  // 设置 超时时间 为5秒                  httpsURLConnection.setConnectTimeout( 5 * 1000 );                  // 通过输入流获取网络xml内容                  // 取得输入流                  InputStream inputStream = httpsURLConnection.getInputStream();                  SAXParserFactory parserFactory = SAXParserFactory.newInstance();                  // 取得SAXParser 实例                  SAXParser parser = parserFactory.newSAXParser();                  parser.parse(inputStream, this );                  return list;            }            @Override          public void characters( char [] ch, int start, int length)                          throws SAXException {                  if ( null != tag && ! "" .equals(tag)) {                          if (javaBean != null ) {                                  String data = new String(ch, start, length);                                  Field[] fields = javaBean.getClass().getDeclaredFields();                                  for ( int i = 0 ; i < fields.length; i++) {                                          if (tag.equalsIgnoreCase(fields[i].getName())) {                                                  setAttribute(javaBean, fields[i].getName(), data,                                                                  new Class[] { fields[i].getType() });                                          }                                    }                            }                    }            }            @Override          public void endDocument() throws SAXException {          }            @Override          public void endElement(String uri, String localName, String qName)                          throws SAXException {                  if ( null != localName && ! "" .equals(localName)) {                          String bean = updateSmall(javaBean.getClass().getSimpleName());                          if (bean.equalsIgnoreCase(localName) && bean != null ) {                                  list.add(javaBean);                          }                  }                  tag = null ;          }            @Override          public void startDocument() throws SAXException {                    // TODO Auto-generated method stub                    list = new ArrayList<Object>();            }            @Override          public void startElement(String uri, String localName, String qName,                          Attributes attributes) throws SAXException {                  tag = qName;                  // 取得实体类简单名称，把首字母变为小 写                  String bean = updateSmall(javaBean.getClass().getSimpleName());                  // 取得实体类的 全限 名称                  String clazz = javaBean.getClass().getName();                  if (bean.equalsIgnoreCase(qName)) {                          try {                                  javaBean = Class.forName(clazz).newInstance();                          } catch (Exception e) {                                  e.printStackTrace();                          }                          Field[] fields = javaBean.getClass().getDeclaredFields();                          for ( int i = 0 ; i < attributes.getLength(); i++) {                                  for ( int j = 0 ; j < fields.length; j++) {                                          if (attributes.getQName(i).equalsIgnoreCase(fields[j].getName())) {                                                  setAttribute(javaBean, attributes.getQName(i),                                                                  attributes.getValue(i),                                                                  new Class[] { fields[j].getType() });                                          }                                  }                          }                  }          }            /**           * @param object           *            类           * @param setName           *            方法名           * @param setValue方法设置           * @param obj           *            属性类型           * @throws Exception           */          public void setAttribute(Object object, String setName,                          String setValue, Class[] obj) {                  Method method;                  try {                          method = object.getClass().getMethod(                                          "set" + updateStr(setName), obj[ 0 ]);                          if (obj[ 0 ].equals(Integer. class ) || obj[ 0 ].equals( int . class )) {                                  method.invoke(object, new Integer(setValue));                          }                          if (obj[ 0 ].equals(Float. class ) || obj[ 0 ].equals( float . class )) {                                  method.invoke(object, new Float(setValue));                          }                          if (obj[ 0 ].equals(Short. class ) || obj[ 0 ].equals( short . class )) {                                  method.invoke(object, new Short(setValue));                          }                          if (obj[ 0 ].equals(Byte. class ) || obj[ 0 ].equals( byte . class )) {                                  method.invoke(object, new Byte(setValue));                          }                          if (obj[ 0 ].equals(Double. class ) || obj[ 0 ].equals( double . class )) {                                  method.invoke(object, new Double(setValue));                          }                          if (obj[ 0 ].equals(Date. class )) {                                  method.invoke(object, new Date( new Long(setValue)));                          }                          if (obj[ 0 ].equals(java.util.Date. class )) {                                  method.invoke(object, new java.util.Date(setValue));                          }                          if (obj[ 0 ].equals(Long. class ) || obj[ 0 ].equals( long . class )) {                                  method.invoke(object, new Long(setValue));                          }                          if (obj[ 0 ].equals(Boolean. class )                                          || obj[ 0 ].equals( boolean . class )) {                                  method.invoke(object, new Boolean(setValue));                          }                          if (obj[ 0 ].equals(String. class )) {                                  method.invoke(object, setValue);                          }                  } catch (Exception e) {                          e.printStackTrace();                  }            }            /**           * 把字符串的首字母改为大写           *           * @param str           * @return String           */          public String updateStr(String str) {                  char c = ( char ) (str.charAt( 0 ) - 32 );                  String s = str.substring( 1 , str.length());                  return c + s;          }            /**           * 把字符串的首字母改为小写           *           * @param str           * @return String           */            public String updateSmall(String str) {                  char c = ( char ) (str.charAt( 0 ) + 32 );                  String s = str.substring( 1 , str.length());                  return c + s;          } }

(4)权限配置 ，AndroidManifest.xml  配置权限代码:

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(5)解析测试：

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@Override protected void onCreate(Bundle savedInstanceState) {            super .onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            SAXParserContentHandler contentHandler = new SAXParserContentHandler();            List<Object> list;          Plant plant = new Plant();          try {                  SimpleDateFormat formatter = new SimpleDateFormat ( "yyyy-MM-dd HH:mm:ss S " );                                     Date curDate = new Date(System.currentTimeMillis()); //获取当前时间                                     String str = formatter.format(curDate);                  System.out.println( " 开始时间为 ：" +str );          list = contentHandler.parseReadXml( "http://www.w3school.com.cn/example/xmle/plant_catalog.xml" ,plant);          System.out.println( list.size()+ "　　AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA " );                  for (Object object : list) {                          Plant pants=(Plant )object;                           System.out.println( "普通种类:" +pants.getCommon());                           System.out.println( " 植物名称:" +pants.getBotanical() );                          System.out.println( "地区:" +pants.getZone() );                          System.out.println( "可用性:" +pants.getAvailability());            Log.d( "Pull Helper" , "Pull Helpe:" +pants.getBotanical()+ "可用性:" +pants.getAvailability());                          }                                    Date curend = new Date(System.currentTimeMillis()); //获取当前时间                                     String strend = formatter.format(curend);                  System.out.println( " 结束时间为 ：" +strend );          } catch (Exception e) {                  // System.out.println("   %%%%%%%%%%%%%%&&&&&&&&&&&&&&&&&&&&&&&     "+e.getMessage());                  e.printStackTrace();          }   }

3.应注意问题：
1)如果要解析网络XML文件，就需要在在AndroidManifest.xml  配置权限，代码为：
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
如果不加权限代码会出现：
XML文法正常解析，使用LogCat可以再告警（W）中看到  Permission denied （没有权限；拒绝访问
）异常信息
2)如果XML文件放置在本地服务器（自己的PC机，XMl运行在其他环节中，如 JAVA ，PHP），在访问是需要设置静态IP地址，访问是使用静态IP地址访问：
如： http://192.85.1.235/mms/index.php?controller=default  
如果直接使用  http://localhost/mms/index.php?controller=default   就会报：Connection refused（连接拒绝）
3)如果使用助手类解析XML，在根据XML标签生成对应Model（实体）时，应注意，Model实体名称必须和目标根目录名称忽略大小后保持一致生成实体所定义的属性名称必须和XML目标标签下的属性标签名称保持一致：
<?xml version="1.0" encoding="UTF-8" ?> 
<CATALOG> 
<PLANT> 
<COMMON>Bloodroot</COMMON> 
<BOTANICAL>Sanguinaria canadensis</BOTANICAL>
<ZONE>4</ZONE> 
<LIGHT>Mostly Shady</LIGHT>
<PRICE>$2.44</PRICE> 
<AVAILABILITY>031599</AVAILABILITY> 
</PLANT>
</CATALOG>
       对应Model实体类名称应该为： Plant ，不然的话解析过程中不会报异常，只是解析结果为空，因为解析方法通过传递参数Model对象实例找到对应的Model类名称，并使用它调getClass().getDeclaredFields()获取实体中定义的属性（XML目标标签下的属性标签，如 name  ,price ,description）；
      如果实体所定义的属性名称必须和XML目标标签下的属性标签名称保持不一样，就无法把XML标签内容赋值给对应实体的属性，对应实体属性解析结果为null ;