android XML解析技术

XML在各种开发中都广泛应用，Android也不例外。作为承载数据的一个重要角色，如何读写XML成为Android开发中一项重要的技能。今天就由我向大家介绍一下在Android平台下几种常见的XML解析和创建的方法。

在Android中，常见的XML解析器分别为SAX解析器、DOM解析器和PULL解析器，下面，我将一一向大家详细介绍。

SAX解析器：

SAX(Simple API for XML)解析器是一种基于事件的解析器，它的核心是事件处理模式，主要是围绕着事件源以及事件处理器来工作的。当事件源产生事件后，调用事件处理器相应的处理方法，一个事件就可以得到处理。在事件源调用事件处理器中特定方法的时候，还要传递给事件处理器相应事件的状态信息，这样事件处理器才能够根据提供的事件信息来决定自己的行为。

SAX解析器的优点是解析速度快，占用内存少。非常适合在Android移动设备中使用。

DOM解析器：

DOM是基于树形结构的的节点或信息片段的集合，允许开发人员使用DOM API遍历XML树、检索所需数据。分析该结构通常需要加载整个文档和构造树形结构，然后才可以检索和更新节点信息。

由于DOM在内存中以树形结构存放，因此检索和更新效率会更高。但是对于特别大的文档，解析和加载整个文档将会很耗资源。

PULL解析器：

PULL解析器的运行方式和SAX类似，都是基于事件的模式。不同的是，在PULL解析过程中，我们需要自己获取产生的事件然后做相应的操作，而不像SAX那样由处理器触发一种事件的方法，执行我们的代码。PULL解析器小巧轻便，解析速度快，简单易用，非常适合在Android移动设备中使用，Android系统内部在解析各种XML时也是用PULL解析器。

以上三种解析器，都是非常实用的解析器，我将会一一介绍。我们将会使用这三种解析技术完成一项共同的任务。

我们新建一个项目，项目结构如下：

我会在项目的assets目录中放置一个XML文档books.xml，内容如下：

[xhtml] view plain copy print ?

<?xmlversion="1.0"encoding="utf-8"?>
<books>
<book>
<id>1001</id>
<name>ThinkingInJava</name>
<price>80.00</price>
</book>
<book>
<id>1002</id>
<name>CoreJava</name>
<price>90.00</price>
</book>
<book>
<id>1003</id>
<name>Hello,Andriod</name>
<price>100.00</price>
</book>
</books>

<?xml version="1.0" encoding="utf-8"?> <books> <book> <id>1001</id> <name>Thinking In Java</name> <price>80.00</price> </book> <book> <id>1002</id> <name>Core Java</name> <price>90.00</price> </book> <book> <id>1003</id> <name>Hello, Andriod</name> <price>100.00</price> </book> </books>

然后我们分别使用以上三种解析技术解析文档，得到一个List<Book>的对象，先来看一下Book.java的代码：

[java] view plain copy print ?

packagecom.scott.xml.model;
publicclassBook{
privateintid;
privateStringname;
privatefloatprice;
publicintgetId(){
returnid;
}
publicvoidsetId(intid){
this.id=id;
}
publicStringgetName(){
returnname;
}
publicvoidsetName(Stringname){
this.name=name;
}
publicfloatgetPrice(){
returnprice;
}
publicvoidsetPrice(floatprice){
this.price=price;
}
@Override
publicStringtoString(){
return"id:"+id+",name:"+name+",price:"+price;
}
}

package com.scott.xml.model; public class Book { private int id; private String name; private float price; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public float getPrice() { return price; } public void setPrice(float price) { this.price = price; } @Override public String toString() { return "id:" + id + ", name:" + name + ", price:" + price; } }

最后，我们还要把这个集合对象中的数据生成一个新的XML文档，如图：

生成的XML结构跟原始文档略有不同，是下面这种格式：

[xhtml] view plain copy print ?

<?xmlversion="1.0"encoding="UTF-8"?>
<books>
<bookid="1001">
<name>ThinkingInJava</name>
<price>80.0</price>
</book>
<bookid="1002">
<name>CoreJava</name>
<price>90.0</price>
</book>
<bookid="1003">
<name>Hello,Andriod</name>
<price>100.0</price>
</book>
</books>

<?xml version="1.0" encoding="UTF-8"?> <books> <book id="1001"> <name>Thinking In Java</name> <price>80.0</price> </book> <book id="1002"> <name>Core Java</name> <price>90.0</price> </book> <book id="1003"> <name>Hello, Andriod</name> <price>100.0</price> </book> </books>

接下来，就该介绍操作过程了，我们先为解析器定义一个BookParser接口，每种类型的解析器需要实现此接口。BookParser.java代码如下：

[java] view plain copy print ?

packagecom.scott.xml.parser;
importjava.io.InputStream;
importjava.util.List;
importcom.scott.xml.model.Book;
publicinterfaceBookParser{
/**
*解析输入流得到Book对象集合
*@paramis
*@return
*@throwsException
*/
publicList<Book>parse(InputStreamis)throwsException;
/**
*序列化Book对象集合得到XML形式的字符串
*@parambooks
*@return
*@throwsException
*/
publicStringserialize(List<Book>books)throwsException;
}

package com.scott.xml.parser; import java.io.InputStream; import java.util.List; import com.scott.xml.model.Book; public interface BookParser { /** * 解析输入流得到Book对象集合 * @param is * @return * @throws Exception */ public List<Book> parse(InputStream is) throws Exception; /** * 序列化Book对象集合得到XML形式的字符串 * @param books * @return * @throws Exception */ public String serialize(List<Book> books) throws Exception; }

好了，我们就该一个一个的实现该接口，完成我们的解析过程。

使用SAX解析器：

SaxBookParser.java代码如下：

[c-sharp] view plain copy print ?

packagecom.scott.xml.parser;
importjava.io.InputStream;
importjava.io.StringWriter;
importjava.util.ArrayList;
importjava.util.List;
importjavax.xml.parsers.SAXParser;
importjavax.xml.parsers.SAXParserFactory;
importjavax.xml.transform.OutputKeys;
importjavax.xml.transform.Result;
importjavax.xml.transform.Transformer;
importjavax.xml.transform.TransformerFactory;
importjavax.xml.transform.sax.SAXTransformerFactory;
importjavax.xml.transform.sax.TransformerHandler;
importjavax.xml.transform.stream.StreamResult;
importorg.xml.sax.Attributes;
importorg.xml.sax.SAXException;
importorg.xml.sax.helpers.AttributesImpl;
importorg.xml.sax.helpers.DefaultHandler;
importcom.scott.xml.model.Book;
publicclassSaxBookParserimplementsBookParser{
@Override
publicList<Book>parse(InputStreamis)throwsException{
SAXParserFactoryfactory=SAXParserFactory.newInstance();//取得SAXParserFactory实例
SAXParserparser=factory.newSAXParser();//从factory获取SAXParser实例
MyHandlerhandler=newMyHandler();//实例化自定义Handler
parser.parse(is,handler);//根据自定义Handler规则解析输入流
returnhandler.getBooks();
}
@Override
publicStringserialize(List<Book>books)throwsException{
SAXTransformerFactoryfactory=(SAXTransformerFactory)TransformerFactory.newInstance();//取得SAXTransformerFactory实例
TransformerHandlerhandler=factory.newTransformerHandler();//从factory获取TransformerHandler实例
Transformertransformer=handler.getTransformer();//从handler获取Transformer实例
transformer.setOutputProperty(OutputKeys.ENCODING,"UTF-8");//设置输出采用的编码方式
transformer.setOutputProperty(OutputKeys.INDENT,"yes");//是否自动添加额外的空白
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION,"no");//是否忽略XML声明
StringWriterwriter=newStringWriter();
Resultresult=newStreamResult(writer);
handler.setResult(result);
Stringuri="";//代表命名空间的URI当URI无值时须置为空字符串
StringlocalName="";//命名空间的本地名称(不包含前缀)当没有进行命名空间处理时须置为空字符串
handler.startDocument();
handler.startElement(uri,localName,"books",null);
AttributesImplattrs=newAttributesImpl();//负责存放元素的属性信息
char[]ch=null;
for(Bookbook:books){
attrs.clear();//清空属性列表
attrs.addAttribute(uri,localName,"id","string",String.valueOf(book.getId()));//添加一个名为id的属性(type影响不大,这里设为string)
handler.startElement(uri,localName,"book",attrs);//开始一个book元素关联上面设定的id属性
handler.startElement(uri,localName,"name",null);//开始一个name元素没有属性
ch=String.valueOf(book.getName()).toCharArray();
handler.characters(ch,0,ch.length);//设置name元素的文本节点
handler.endElement(uri,localName,"name");
handler.startElement(uri,localName,"price",null);//开始一个price元素没有属性
ch=String.valueOf(book.getPrice()).toCharArray();
handler.characters(ch,0,ch.length);//设置price元素的文本节点
handler.endElement(uri,localName,"price");
handler.endElement(uri,localName,"book");
}
handler.endElement(uri,localName,"books");
handler.endDocument();
returnwriter.toString();
}
//需要重写DefaultHandler的方法
privateclassMyHandlerextendsDefaultHandler{
privateList<Book>books;
privateBookbook;
privateStringBuilderbuilder;
//返回解析后得到的Book对象集合
publicList<Book>getBooks(){
returnbooks;
}
@Override
publicvoidstartDocument()throwsSAXException{
super.startDocument();
books=newArrayList<Book>();
builder=newStringBuilder();
}
@Override
publicvoidstartElement(Stringuri,StringlocalName,StringqName,Attributesattributes)throwsSAXException{
super.startElement(uri,localName,qName,attributes);
if(localName.equals("book")){
book=newBook();
}
builder.setLength(0);//将字符长度设置为0以便重新开始读取元素内的字符节点
}
@Override
publicvoidcharacters(char[]ch,intstart,intlength)throwsSAXException{
super.characters(ch,start,length);
builder.append(ch,start,length);//将读取的字符数组追加到builder中
}
@Override
publicvoidendElement(Stringuri,StringlocalName,StringqName)throwsSAXException{
super.endElement(uri,localName,qName);
if(localName.equals("id")){
book.setId(Integer.parseInt(builder.toString()));
}elseif(localName.equals("name")){
book.setName(builder.toString());
}elseif(localName.equals("price")){
book.setPrice(Float.parseFloat(builder.toString()));
}elseif(localName.equals("book")){
books.add(book);
}
}
}
}

package com.scott.xml.parser; import java.io.InputStream; import java.io.StringWriter; import java.util.ArrayList; import java.util.List; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import javax.xml.transform.OutputKeys; import javax.xml.transform.Result; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.sax.SAXTransformerFactory; import javax.xml.transform.sax.TransformerHandler; import javax.xml.transform.stream.StreamResult; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.AttributesImpl; import org.xml.sax.helpers.DefaultHandler; import com.scott.xml.model.Book; public class SaxBookParser implements BookParser { @Override public List<Book> parse(InputStream is) throws Exception { SAXParserFactory factory = SAXParserFactory.newInstance(); //取得SAXParserFactory实例 SAXParser parser = factory.newSAXParser(); //从factory获取SAXParser实例 MyHandler handler = new MyHandler(); //实例化自定义Handler parser.parse(is, handler); //根据自定义Handler规则解析输入流 return handler.getBooks(); } @Override public String serialize(List<Book> books) throws Exception { SAXTransformerFactory factory = (SAXTransformerFactory) TransformerFactory.newInstance();//取得SAXTransformerFactory实例 TransformerHandler handler = factory.newTransformerHandler(); //从factory获取TransformerHandler实例 Transformer transformer = handler.getTransformer(); //从handler获取Transformer实例 transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // 设置输出采用的编码方式 transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否自动添加额外的空白 transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // 是否忽略XML声明 StringWriter writer = new StringWriter(); Result result = new StreamResult(writer); handler.setResult(result); String uri = ""; //代表命名空间的URI 当URI无值时须置为空字符串 String localName = ""; //命名空间的本地名称(不包含前缀) 当没有进行命名空间处理时须置为空字符串 handler.startDocument(); handler.startElement(uri, localName, "books", null); AttributesImpl attrs = new AttributesImpl(); //负责存放元素的属性信息 char[] ch = null; for (Book book : books) { attrs.clear(); //清空属性列表 attrs.addAttribute(uri, localName, "id", "string", String.valueOf(book.getId()));//添加一个名为id的属性(type影响不大,这里设为string) handler.startElement(uri, localName, "book", attrs); //开始一个book元素关联上面设定的id属性 handler.startElement(uri, localName, "name", null); //开始一个name元素没有属性 ch = String.valueOf(book.getName()).toCharArray(); handler.characters(ch, 0, ch.length); //设置name元素的文本节点 handler.endElement(uri, localName, "name"); handler.startElement(uri, localName, "price", null);//开始一个price元素没有属性 ch = String.valueOf(book.getPrice()).toCharArray(); handler.characters(ch, 0, ch.length); //设置price元素的文本节点 handler.endElement(uri, localName, "price"); handler.endElement(uri, localName, "book"); } handler.endElement(uri, localName, "books"); handler.endDocument(); return writer.toString(); } //需要重写DefaultHandler的方法 private class MyHandler extends DefaultHandler { private List<Book> books; private Book book; private StringBuilder builder; //返回解析后得到的Book对象集合 public List<Book> getBooks() { return books; } @Override public void startDocument() throws SAXException { super.startDocument(); books = new ArrayList<Book>(); builder = new StringBuilder(); } @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { super.startElement(uri, localName, qName, attributes); if (localName.equals("book")) { book = new Book(); } builder.setLength(0); //将字符长度设置为0 以便重新开始读取元素内的字符节点 } @Override public void characters(char[] ch, int start, int length) throws SAXException { super.characters(ch, start, length); builder.append(ch, start, length); //将读取的字符数组追加到builder中 } @Override public void endElement(String uri, String localName, String qName) throws SAXException { super.endElement(uri, localName, qName); if (localName.equals("id")) { book.setId(Integer.parseInt(builder.toString())); } else if (localName.equals("name")) { book.setName(builder.toString()); } else if (localName.equals("price")) { book.setPrice(Float.parseFloat(builder.toString())); } else if (localName.equals("book")) { books.add(book); } } } }

代码中，我们定义了自己的事件处理逻辑，重写了DefaultHandler的几个重要的事件方法。下面我为大家着重介绍一下DefaultHandler的相关知识。DefaultHandler是一个事件处理器，可以接收解析器报告的所有事件，处理所发现的数据。它实现了EntityResolver接口、DTDHandler接口、ErrorHandler接口和ContentHandler接口。这几个接口代表不同类型的事件处理器。我们着重介绍一下ContentHandler接口。结构如图：

这几个比较重要的方法已被我用红线标注，DefaultHandler实现了这些方法，但在方法体内没有做任何事情，因此我们在使用时必须覆写相关的方法。最重要的是startElement方法、characters方法和endElement方法。当执行文档时遇到起始节点，startElement方法将会被调用，我们可以获取起始节点相关信息；然后characters方法被调用，我们可以获取节点内的文本信息；最后endElement方法被调用，我们可以做收尾的相关操作。

最后，我们需要调用SAX解析程序，这个步骤在MainActivity中完成：

[java] view plain copy print ?

packagecom.scott.xml;
importjava.io.FileOutputStream;
importjava.io.InputStream;
importjava.util.List;
importandroid.app.Activity;
importandroid.content.Context;
importandroid.os.Bundle;
importandroid.util.Log;
importandroid.view.View;
importandroid.widget.Button;
importcom.scott.xml.model.Book;
importcom.scott.xml.parser.BookParser;
importcom.scott.xml.parser.SaxBookParser;
publicclassMainActivityextendsActivity{
privatestaticfinalStringTAG="XML";
privateBookParserparser;
privateList<Book>books;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ButtonreadBtn=(Button)findViewById(R.id.readBtn);
ButtonwriteBtn=(Button)findViewById(R.id.writeBtn);
readBtn.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
try{
InputStreamis=getAssets().open("books.xml");
parser=newSaxBookParser();//创建SaxBookParser实例
books=parser.parse(is);//解析输入流
for(Bookbook:books){
Log.i(TAG,book.toString());
}
}catch(Exceptione){
Log.e(TAG,e.getMessage());
}
}
});
writeBtn.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
try{
Stringxml=parser.serialize(books);//序列化
FileOutputStreamfos=openFileOutput("books.xml",Context.MODE_PRIVATE);
fos.write(xml.getBytes("UTF-8"));
}catch(Exceptione){
Log.e(TAG,e.getMessage());
}
}
});
}
}

package com.scott.xml; import java.io.FileOutputStream; import java.io.InputStream; import java.util.List; import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import com.scott.xml.model.Book; import com.scott.xml.parser.BookParser; import com.scott.xml.parser.SaxBookParser; public class MainActivity extends Activity { private static final String TAG = "XML"; private BookParser parser; private List<Book> books; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button readBtn = (Button) findViewById(R.id.readBtn); Button writeBtn = (Button) findViewById(R.id.writeBtn); readBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { try { InputStream is = getAssets().open("books.xml"); parser = new SaxBookParser(); //创建SaxBookParser实例 books = parser.parse(is); //解析输入流 for (Book book : books) { Log.i(TAG, book.toString()); } } catch (Exception e) { Log.e(TAG, e.getMessage()); } } }); writeBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { try { String xml = parser.serialize(books); //序列化 FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE); fos.write(xml.getBytes("UTF-8")); } catch (Exception e) { Log.e(TAG, e.getMessage()); } } }); } }

界面就两个按钮，顺便给大家贴上：

点击“readXML”按钮，将会调用SAX解析器解析文档，并在日志台打印相关信息：

然后再点击“writeXML”按钮，将会在该应用包下的files目录生成一个books.xml文件：

使用DOM解析器：

DomBookParser.java代码如下：

[java] view plain copy print ?

packagecom.scott.xml.parser;
importjava.io.InputStream;
importjava.io.StringWriter;
importjava.util.ArrayList;
importjava.util.List;
importjavax.xml.parsers.DocumentBuilder;
importjavax.xml.parsers.DocumentBuilderFactory;
importjavax.xml.transform.OutputKeys;
importjavax.xml.transform.Result;
importjavax.xml.transform.Source;
importjavax.xml.transform.Transformer;
importjavax.xml.transform.TransformerFactory;
importjavax.xml.transform.dom.DOMSource;
importjavax.xml.transform.stream.StreamResult;
importorg.w3c.dom.Document;
importorg.w3c.dom.Element;
importorg.w3c.dom.Node;
importorg.w3c.dom.NodeList;
importcom.scott.xml.model.Book;
publicclassDomBookParserimplementsBookParser{
@Override
publicList<Book>parse(InputStreamis)throwsException{
List<Book>books=newArrayList<Book>();
DocumentBuilderFactoryfactory=DocumentBuilderFactory.newInstance();//取得DocumentBuilderFactory实例
DocumentBuilderbuilder=factory.newDocumentBuilder();//从factory获取DocumentBuilder实例
Documentdoc=builder.parse(is);//解析输入流得到Document实例
ElementrootElement=doc.getDocumentElement();
NodeListitems=rootElement.getElementsByTagName("book");
for(inti=0;i<items.getLength();i++){
Bookbook=newBook();
Nodeitem=items.item(i);
NodeListproperties=item.getChildNodes();
for(intj=0;j<properties.getLength();j++){
Nodeproperty=properties.item(j);
StringnodeName=property.getNodeName();
if(nodeName.equals("id")){
book.setId(Integer.parseInt(property.getFirstChild().getNodeValue()));
}elseif(nodeName.equals("name")){
book.setName(property.getFirstChild().getNodeValue());
}elseif(nodeName.equals("price")){
book.setPrice(Float.parseFloat(property.getFirstChild().getNodeValue()));
}
}
books.add(book);
}
returnbooks;
}
@Override
publicStringserialize(List<Book>books)throwsException{
DocumentBuilderFactoryfactory=DocumentBuilderFactory.newInstance();
DocumentBuilderbuilder=factory.newDocumentBuilder();
Documentdoc=builder.newDocument();//由builder创建新文档
ElementrootElement=doc.createElement("books");
for(Bookbook:books){
ElementbookElement=doc.createElement("book");
bookElement.setAttribute("id",book.getId()+"");
ElementnameElement=doc.createElement("name");
nameElement.setTextContent(book.getName());
bookElement.appendChild(nameElement);
ElementpriceElement=doc.createElement("price");
priceElement.setTextContent(book.getPrice()+"");
bookElement.appendChild(priceElement);
rootElement.appendChild(bookElement);
}
doc.appendChild(rootElement);
TransformerFactorytransFactory=TransformerFactory.newInstance();//取得TransformerFactory实例
Transformertransformer=transFactory.newTransformer();//从transFactory获取Transformer实例
transformer.setOutputProperty(OutputKeys.ENCODING,"UTF-8");//设置输出采用的编码方式
transformer.setOutputProperty(OutputKeys.INDENT,"yes");//是否自动添加额外的空白
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION,"no");//是否忽略XML声明
StringWriterwriter=newStringWriter();
Sourcesource=newDOMSource(doc);//表明文档来源是doc
Resultresult=newStreamResult(writer);//表明目标结果为writer
transformer.transform(source,result);//开始转换
returnwriter.toString();
}
}

package com.scott.xml.parser; import java.io.InputStream; import java.io.StringWriter; import java.util.ArrayList; import java.util.List; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.OutputKeys; import javax.xml.transform.Result; import javax.xml.transform.Source; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import com.scott.xml.model.Book; public class DomBookParser implements BookParser { @Override public List<Book> parse(InputStream is) throws Exception { List<Book> books = new ArrayList<Book>(); DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); //取得DocumentBuilderFactory实例 DocumentBuilder builder = factory.newDocumentBuilder(); //从factory获取DocumentBuilder实例 Document doc = builder.parse(is); //解析输入流得到Document实例 Element rootElement = doc.getDocumentElement(); NodeList items = rootElement.getElementsByTagName("book"); for (int i = 0; i < items.getLength(); i++) { Book book = new Book(); Node item = items.item(i); NodeList properties = item.getChildNodes(); for (int j = 0; j < properties.getLength(); j++) { Node property = properties.item(j); String nodeName = property.getNodeName(); if (nodeName.equals("id")) { book.setId(Integer.parseInt(property.getFirstChild().getNodeValue())); } else if (nodeName.equals("name")) { book.setName(property.getFirstChild().getNodeValue()); } else if (nodeName.equals("price")) { book.setPrice(Float.parseFloat(property.getFirstChild().getNodeValue())); } } books.add(book); } return books; } @Override public String serialize(List<Book> books) throws Exception { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document doc = builder.newDocument(); //由builder创建新文档 Element rootElement = doc.createElement("books"); for (Book book : books) { Element bookElement = doc.createElement("book"); bookElement.setAttribute("id", book.getId() + ""); Element nameElement = doc.createElement("name"); nameElement.setTextContent(book.getName()); bookElement.appendChild(nameElement); Element priceElement = doc.createElement("price"); priceElement.setTextContent(book.getPrice() + ""); bookElement.appendChild(priceElement); rootElement.appendChild(bookElement); } doc.appendChild(rootElement); TransformerFactory transFactory = TransformerFactory.newInstance();//取得TransformerFactory实例 Transformer transformer = transFactory.newTransformer(); //从transFactory获取Transformer实例 transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // 设置输出采用的编码方式 transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否自动添加额外的空白 transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // 是否忽略XML声明 StringWriter writer = new StringWriter(); Source source = new DOMSource(doc); //表明文档来源是doc Result result = new StreamResult(writer);//表明目标结果为writer transformer.transform(source, result); //开始转换 return writer.toString(); } }

然后再MainActivity中只需改一个地方：

[java] view plain copy print ?

readBtn.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
try{
InputStreamis=getAssets().open("books.xml");
//parser=newSaxBookParser();
parser=newDomBookParser();
books=parser.parse(is);
for(Bookbook:books){
Log.i(TAG,book.toString());
}
}catch(Exceptione){
Log.e(TAG,e.getMessage());
}
}
);

readBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { try { InputStream is = getAssets().open("books.xml"); // parser = new SaxBookParser(); parser = new DomBookParser(); books = parser.parse(is); for (Book book : books) { Log.i(TAG, book.toString()); } } catch (Exception e) { Log.e(TAG, e.getMessage()); } } });

执行结果是一样的。

使用PULL解析器：

PullBookParser.java代码如下：

[java] view plain copy print ?

packagecom.scott.xml.parser;
importjava.io.InputStream;
importjava.io.StringWriter;
importjava.util.ArrayList;
importjava.util.List;
importorg.xmlpull.v1.XmlPullParser;
importorg.xmlpull.v1.XmlSerializer;
importandroid.util.Xml;
importcom.scott.xml.model.Book;
publicclassPullBookParserimplementsBookParser{
@Override
publicList<Book>parse(InputStreamis)throwsException{
List<Book>books=null;
Bookbook=null;
//XmlPullParserFactoryfactory=XmlPullParserFactory.newInstance();
//XmlPullParserparser=factory.newPullParser();
XmlPullParserparser=Xml.newPullParser();//由android.util.Xml创建一个XmlPullParser实例
parser.setInput(is,"UTF-8");//设置输入流并指明编码方式
inteventType=parser.getEventType();
while(eventType!=XmlPullParser.END_DOCUMENT){
switch(eventType){
caseXmlPullParser.START_DOCUMENT:
books=newArrayList<Book>();
break;
caseXmlPullParser.START_TAG:
if(parser.getName().equals("book")){
book=newBook();
}elseif(parser.getName().equals("id")){
eventType=parser.next();
book.setId(Integer.parseInt(parser.getText()));
}elseif(parser.getName().equals("name")){
eventType=parser.next();
book.setName(parser.getText());
}elseif(parser.getName().equals("price")){
eventType=parser.next();
book.setPrice(Float.parseFloat(parser.getText()));
}
break;
caseXmlPullParser.END_TAG:
if(parser.getName().equals("book")){
books.add(book);
book=null;
}
break;
}
eventType=parser.next();
}
returnbooks;
}
@Override
publicStringserialize(List<Book>books)throwsException{
//XmlPullParserFactoryfactory=XmlPullParserFactory.newInstance();
//XmlSerializerserializer=factory.newSerializer();
XmlSerializerserializer=Xml.newSerializer();//由android.util.Xml创建一个XmlSerializer实例
StringWriterwriter=newStringWriter();
serializer.setOutput(writer);//设置输出方向为writer
serializer.startDocument("UTF-8",true);
serializer.startTag("","books");
for(Bookbook:books){
serializer.startTag("","book");
serializer.attribute("","id",book.getId()+"");
serializer.startTag("","name");
serializer.text(book.getName());
serializer.endTag("","name");
serializer.startTag("","price");
serializer.text(book.getPrice()+"");
serializer.endTag("","price");
serializer.endTag("","book");
}
serializer.endTag("","books");
serializer.endDocument();
returnwriter.toString();
}
}

package com.scott.xml.parser; import java.io.InputStream; import java.io.StringWriter; import java.util.ArrayList; import java.util.List; import org.xmlpull.v1.XmlPullParser; import org.xmlpull.v1.XmlSerializer; import android.util.Xml; import com.scott.xml.model.Book; public class PullBookParser implements BookParser { @Override public List<Book> parse(InputStream is) throws Exception { List<Book> books = null; Book book = null; // XmlPullParserFactory factory = XmlPullParserFactory.newInstance(); // XmlPullParser parser = factory.newPullParser(); XmlPullParser parser = Xml.newPullParser(); //由android.util.Xml创建一个XmlPullParser实例 parser.setInput(is, "UTF-8"); //设置输入流并指明编码方式 int eventType = parser.getEventType(); while (eventType != XmlPullParser.END_DOCUMENT) { switch (eventType) { case XmlPullParser.START_DOCUMENT: books = new ArrayList<Book>(); break; case XmlPullParser.START_TAG: if (parser.getName().equals("book")) { book = new Book(); } else if (parser.getName().equals("id")) { eventType = parser.next(); book.setId(Integer.parseInt(parser.getText())); } else if (parser.getName().equals("name")) { eventType = parser.next(); book.setName(parser.getText()); } else if (parser.getName().equals("price")) { eventType = parser.next(); book.setPrice(Float.parseFloat(parser.getText())); } break; case XmlPullParser.END_TAG: if (parser.getName().equals("book")) { books.add(book); book = null; } break; } eventType = parser.next(); } return books; } @Override public String serialize(List<Book> books) throws Exception { // XmlPullParserFactory factory = XmlPullParserFactory.newInstance(); // XmlSerializer serializer = factory.newSerializer(); XmlSerializer serializer = Xml.newSerializer(); //由android.util.Xml创建一个XmlSerializer实例 StringWriter writer = new StringWriter(); serializer.setOutput(writer); //设置输出方向为writer serializer.startDocument("UTF-8", true); serializer.startTag("", "books"); for (Book book : books) { serializer.startTag("", "book"); serializer.attribute("", "id", book.getId() + ""); serializer.startTag("", "name"); serializer.text(book.getName()); serializer.endTag("", "name"); serializer.startTag("", "price"); serializer.text(book.getPrice() + ""); serializer.endTag("", "price"); serializer.endTag("", "book"); } serializer.endTag("", "books"); serializer.endDocument(); return writer.toString(); } }

然后再对MainActivity做以下更改：

[java] view plain copy print ?

readBtn.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewv){
try{
InputStreamis=getAssets().open("books.xml");
//parser=newSaxBookParser();
//parser=newDomBookParser();
parser=newPullBookParser();
books=parser.parse(is);
for(Bookbook:books){
Log.i(TAG,book.toString());
}
}catch(Exceptione){
Log.e(TAG,e.getMessage());
}
}
});

readBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { try { InputStream is = getAssets().open("books.xml"); // parser = new SaxBookParser(); // parser = new DomBookParser(); parser = new PullBookParser(); books = parser.parse(is); for (Book book : books) { Log.i(TAG, book.toString()); } } catch (Exception e) { Log.e(TAG, e.getMessage()); } } });

和其他两个执行结果都一样。

对于这三种解析器各有优点，我个人比较倾向于PULL解析器，因为SAX解析器操作起来太笨重，DOM不适合文档较大，内存较小的场景，唯有PULL轻巧灵活，速度快，占用内存小，使用非常顺手。读者也可以根据自己的喜好选择相应的解析技术

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