Android创建与解析XML（三）――详解Sax方式

2019-12-12 04:28:39

字体：大中小

来源：转载

供稿：网友

1. Sax概述

SAX是一种占用内存少且解析速度快的解析器，它采用的是事件启动，不需要解析完整个文档，而是按照内容顺序看文档某个部分是否符合xml语法，如果符合就触发相应的事件，所谓的事件就是些回调方法（callback），这些方法定义在ContentHandler中，下面是其主要方法：

startDocument（）：当遇到文档的时候就触发这个事件调用这个方法可以在其中做些预处理工作，如：申请对象资源

endDocument（）：当结束文档的时候就触发这个事件调用这个方法可以在其中做些善后工作，如：释放申请的对象资源

startElement（String namespaceURI, String localName, String qName, Attributes atts）：当遇开始标签的时候就会触发这个方法。

endElement（String uri, String localName, String name）：当遇到结束标签时触发这个事件，调用此法可以做些善后工作。

charachers（char [] ch, int start, int length）：当遇到xml内容时触发这个方法，用new String(ch,start,length)可以接受内容。

Sax方式创建XML，应用了标准xml构造器 javax.xml.transform.sax.TransformerHandler 事件来创建 XML 文档，需要导入以下内容

javax.xml.transform

javax.xml.transform.sax.SAXTransformerFactory;
javax.xml.transform.sax.TransformerHandler;
javax.xml.transform.Transformer;
javax.xml.transform.TransformerConfigurationException;
javax.xml.transform.TransformerFactoryConfigurationError;
javax.xml.transform.OutputKeys;
javax.xml.transform.stream.StreamResult;
javax.xml.transform.sax.SAXTransformerFactory;

javax.xml.parsers

javax.xml.parsers.SAXParser;
javax.xml.parsers.SAXParserFactory;
javax.xml.parsers.FactoryConfigurationError;
javax.xml.parsers.ParserConfigurationException;

org.xml.sax

org.xml.sax.Attributes;
org.xml.sax.SAXException;
org.xml.sax.helpers.AttributesImpl;
org.xml.sax.helpers.DefaultHandler;

Sax 创建和解析 XML 的效果图：

2、Sax 创建 XML

首先，SAXTransformerFactory.newInstance() 创建一个工厂实例 factory

接着，factory.newTransformerHandler() 获取 TransformerHandler 的 handler 对象

然后，通过 handler 事件创建handler.getTransformer()、 handler.setResult(result)，以及 startDocument()、startElement、characters、endElement、endDocument()等

/** Sax方式，创建 XML */ public String saxCreateXML(){   StringWriter xmlWriter = new StringWriter();    Person []persons = new Person[3];    // 创建节点Person对象   persons[0] = new Person(1, "sunboy_2050", "http://blogcsdnnet/sunboy_2050");   persons[1] = new Person(2, "baidu", "http://wwwbaiducom");   persons[2] = new Person(3, "google", "http://wwwgooglecom");      try {     SAXTransformerFactory factory = (SAXTransformerFactory)SAXTransformerFactorynewInstance();     TransformerHandler handler = factorynewTransformerHandler();          Transformer transformer = handlergetTransformer();   // 设置xml属性     transformersetOutputProperty(OutputKeysINDENT, "yes");     transformersetOutputProperty(OutputKeysENCODING, "utf-8");     transformersetOutputProperty(OutputKeysVERSION, "0");          StreamResult result = new StreamResult(xmlWriter);   // 保存创建的xml     handlersetResult(result);          handlerstartDocument();     AttributesImpl attr = new AttributesImpl();          attrclear();     attraddAttribute("", "", "author", "", "homer");     attraddAttribute("", "", "date", "", "2012-04-27");     handlerstartElement("", "", "root", attr);          int personsLen = personslength;     for(int i=0; i<personsLen; i++){       attrclear();       handlerstartElement("", "", "person", attr);              attrclear();       handlerstartElement("", "", "id", attr);       String id = persons[i]getId() + "";       handlercharacters(idtoCharArray(), 0, idlength());       handlerendElement("", "", "id");        attrclear();       handlerstartElement("", "", "name", attr);       String name = persons[i]getName();       handlercharacters(nametoCharArray(), 0, namelength());       handlerendElement("", "", "name");        attrclear();       handlerstartElement("", "", "blog", attr);       String blog = persons[i]getBlog();       handlercharacters(blogtoCharArray(), 0, bloglength());       handlerendElement("", "", "blog");              handlerendElement("", "", "person");     }          handlerendElement("", "", "root");     handlerendDocument();        } catch (TransformerFactoryConfigurationError e) {   // SAXTransformerFactorynewInstance     eprintStackTrace();   } catch (TransformerConfigurationException e) {     // factorynewTransformerHandler     eprintStackTrace();   } catch (IllegalArgumentException e) {   // transformersetOutputProperty     eprintStackTrace();   } catch (SAXException e) {   // handlerstartDocument     eprintStackTrace();   } catch (Exception e) {     eprintStackTrace();   }      savedXML(fileName, xmlWritertoString());   return xmlWritertoString(); }

运行结果：

3、Sax解析XML

  /** Sax方式，解析 XML */   public String saxResolveXML(){     StringWriter xmlWriter = new StringWriter();      InputStream is = readXML(fileName);     try {       SAXParserFactory factory = SAXParserFactorynewInstance();       SAXParser saxParser = factorynewSAXParser();              PersonHandler handler = new PersonHandler();  // person处理Handler       saxParserparse(is, handler);          // handler解析xml              // 获取解析的xml       String xmlHeader = handlergetXMLHeader();       xmlWriterappend(xmlHeader);              List<Person> personsList = handlergetPersons();       int personsLen = personsListsize();       for(int i=0; i<personsLen; i++){         xmlWriterappend(personsListget(i)toString())append("/n");       }            } catch (FactoryConfigurationError e) {     // SAXParserFactorynewInstance       eprintStackTrace();     } catch (ParserConfigurationException e) {   // factorynewSAXParser       eprintStackTrace();     } catch (SAXException e) {     // factorynewSAXParser       eprintStackTrace();     } catch (IllegalArgumentException e) {   // saxParserparse       eprintStackTrace();     } catch (IOException e) {      // saxParserparse       eprintStackTrace();     } catch (Exception e) {       eprintStackTrace();     }          return xmlWritertoString();   }      /** Handler处理类 */   private final class PersonHandler extends DefaultHandler{     private List<Person> personsList = null; // 保存person     private Person person = null;     private StringBuffer xmlHeader;       // 保存xml头部信息     private String tag = null;     // xml Element          /** 返回解析的xml头部信息 */     public String getXMLHeader(){       return xmlHeadertoString();     }          /** 返回解析的Person实例数组 */     public List<Person> getPersons(){       return personsList;     }          @Override     public void startDocument() throws SAXException{       superstartDocument();       personsList = new ArrayList<Person>();       xmlHeader = new StringBuffer();     }          @Override     public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException{       superstartElement(uri, localName, qName, attributes);       if("root"equals(localName)) {         String attrAuthor = attributesgetValue(0);         String attrDate = attributesgetValue(1);         xmlHeaderappend("root")append("/t/t");         xmlHeaderappend(attrAuthor)append("/t");         xmlHeaderappend(attrDate)append("/n");       } else if("person"equals(localName)) {         person = new Person();       }        tag = localName;     }          @Override     public void characters(char[] ch, int start, int length) throws SAXException {       supercharacters(ch, start, length);       if (null != tag) {         String value = new String(ch, start, length);         Systemoutprintln("value = " + value);         if ("id"equals(tag)) {           personsetId(new Integer(value));         } else if ("name"equals(tag)) {           personsetName(value);         } else if ("blog"equals(tag)) {           personsetBlog(value);         }       }     }          @Override     public void endElement(String uri, String localName, String qName) throws SAXException {       if("person"equals(qName)) {         personsListadd(person);         person = null;       }       tag = null;       superendElement(uri, localName, qName);     }          @Override     public void endDocument() throws SAXException{ //     personsList = null;       superendDocument();     }   }

运行结果：