Android三种方式解析Xml

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

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。

下面我们做一个demo来具体实现下

首先在Androidmanifest.xml中添加权限，此权限用于输出xml文件

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

departments.xml被解析的xml文件

<?xml version="1.0" encoding="utf-8"?>
<department>
<person>
<id>1001</id>
<name>张三</name>
<salary>8000.0</salary>
</person>
<person>
<id>1002</id>
<name>李四</name>
<salary>9000.0</salary>
</person>
<person>
<id>1003</id>
<name>王五</name>
<salary>10000.0</salary>
</person>
</department>

封装实体类Department

public class Department {

private int id;

private String name;

private float salary;

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 getSalary() {
return salary;
}

public void setSalary(float salary) {
this.salary = salary;
}

@Override
public String toString() {
// TODO Auto-generated method stub
return "id:" + id + ", name:" + name + ", salary:" + salary;
}

}

为解析器定义一个DepartParser接口，每种类型的解析器需要实现此接口

public interface DepartParser {

/**
* 解析输入流 得到Department对象集合
* @param is
* @return
* @throws Exception
*/
public List<Department> parse(InputStream is) throws Exception;

/**
* 序列化Department对象集合，得到XML形式的字符串
* @param departs
* @return
* @throws Exception
*/
public String serialize(List<Department> departs) throws Exception;
}

serialize(List<Department>)解析出来的数据样式如下：

<?xml version="1.0" encoding="utf-8"?>
<department>
<person id="1001">
<name>张三</name>
<salary>8000.0</salary>
</person>
<person id="1002">
<name>李四</name>
<salary>9000.0</salary>
</person>
<person id="1003">
<name>王五</name>
<salary>10000.0</salary>
</person>
</department>

使用SAX解析

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;

/**
* Sax方式解析
*
* @author 孟祥程
*
*/
public class SaxDepartmentParser implements DepartParser {

@Override
public List<Department> parse(InputStream is) throws Exception {
// TODO Auto-generated method stub
// 取得SAXParserFactory实例
SAXParserFactory factory = SAXParserFactory.newInstance();
// 从factory获取SAXParser实例
SAXParser parser = factory.newSAXParser();
// 实例化自定义Handler
MyHandler handler = new MyHandler();
// 根据自定义Handler规则解析输入流
parser.parse(is, handler);
return handler.getDeparts();
}

@Override
public String serialize(List<Department> departs) throws Exception {
// TODO Auto-generated method stub
SAXTransformerFactory factory = (SAXTransformerFactory) TransformerFactory
.newInstance();
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();这样的话，handler.startDocument()会报 No output specified异常
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, "department", null);

AttributesImpl attrs = new AttributesImpl();   //负责存放元素的属性信息
char[] ch = null;

for (Department depart : departs) {
attrs.clear();  //清空属性列表
attrs.addAttribute(uri, localName, "id", "string", String.valueOf(depart.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, "person", attrs);    //开始一个元素 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(depart.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, "salary", null);//开始一个price元素 没有属性
ch = String.valueOf(depart.getSalary()).toCharArray();
handler.characters(ch, 0, ch.length);   //设置price元素的文本节点
handler.endElement(uri, localName, "salary");

handler.endElement(uri, localName, "person");
}
handler.endElement(uri, localName, "department");
handler.endDocument();

return writer.toString();

}

/**
* 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
*
* @author 孟祥程
*
*/
private class MyHandler extends DefaultHandler {
private List<Department> departs;
private Department depart;
private StringBuilder builder;

// 返回解析后得到的<span class="KSFIND_CLASS" id="2KSFindDIV">Department</span>对象集合
public List<Department> getDeparts() {
return departs;
}

@Override
public void startDocument() throws SAXException {
// TODO Auto-generated method stub
super.startDocument();
departs = new ArrayList<Department>();
builder = new StringBuilder();
}

@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
// TODO Auto-generated method stub
super.startElement(uri, localName, qName, attributes);
if (localName.equals("person")) {
depart = new Department();
}
// 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
builder.setLength(0);
}

@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
super.characters(ch, start, length);
// 将读取的字符数组追加到builder中
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 {
// TODO Auto-generated method stub
super.endElement(uri, localName, qName);
if (localName.equals("id")) {
depart.setId(Integer.parseInt(builder.toString()));
} else if (localName.equals("name")) {
depart.setName(builder.toString());
} else if (localName.equals("salary")) {
depart.setSalary(Float.parseFloat(builder.toString()));
} else if (localName.equals("person")) {
departs.add(depart);
}
}

}

}

使用DOM解析方式

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;

public class DomDepartmentParser implements DepartParser{

@Override
public List<Department> parse(InputStream is) throws Exception {
// TODO Auto-generated method stub
List<Department> <span class="KSFIND_CLASS" id="3KSFindDIV">depart</span>s  = new ArrayList<Department>();
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("person");
for (int i = 0; i < items.getLength(); i++) {
Department depart = new Department();
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")) {
depart.setId(Integer.parseInt(property.getFirstChild().getNodeValue()));
} else if (nodeName.equals("name")) {
depart.setName(property.getFirstChild().getNodeValue());
} else if (nodeName.equals("salary")) {
depart.setSalary(Float.parseFloat(property.getFirstChild().getNodeValue()));
}
}
<span class="KSFIND_CLASS" id="4KSFindDIV">depart</span>s.add(depart);
}
return <span class="KSFIND_CLASS" id="5KSFindDIV">depart</span>s;
}

@Override
public String serialize(List<Department> departs) throws Exception {
// TODO Auto-generated method stub
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.newDocument();   //由builder创建新文档

Element rootElement = doc.createElement("department");

for (Department depart : departs) {
Element <span class="KSFIND_CLASS" id="6KSFindDIV">depart</span>Element = doc.createElement("person");
<span class="KSFIND_CLASS" id="7KSFindDIV">depart</span>Element.setAttribute("id", depart.getId() + "");

Element nameElement = doc.createElement("name");
nameElement.setTextContent(depart.getName());
<span class="KSFIND_CLASS" id="8KSFindDIV">depart</span>Element.appendChild(nameElement);

Element priceElement = doc.createElement("salary");
priceElement.setTextContent(depart.getSalary() + "");
<span class="KSFIND_CLASS" id="9KSFindDIV">depart</span>Element.appendChild(priceElement);

rootElement.appendChild(<span class="KSFIND_CLASS" id="10KSFindDIV">depart</span>Element);
}

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();
}

}

使用PULL解析

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;

public class PullDepartmentParser implements DepartParser {

@Override
public List<Department> parse(InputStream is) throws Exception {
List<Department> departs = null;
Department depart = null;

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:
departs = new ArrayList<Department>();
break;
case XmlPullParser.START_TAG:
if (parser.getName().equals("person")) {
depart = new Department();
} else if (parser.getName().equals("id")) {
eventType = parser.next();
depart.setId(Integer.parseInt(parser.getText()));
} else if (parser.getName().equals("name")) {
eventType = parser.next();
depart.setName(parser.getText());
} else if (parser.getName().equals("salary")) {
eventType = parser.next();
depart.setSalary(Float.parseFloat(parser.getText()));
}
break;
case XmlPullParser.END_TAG:
if (parser.getName().equals("person")) {
departs.add(depart);
depart = null;
}
break;
}
eventType = parser.next();
}
return departs;
}

@Override
public String serialize(List<Department> departs) throws Exception {

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("", "department");
for (Department depart : departs) {
serializer.startTag("", "person");
serializer.attribute("", "id", depart.getId() + "");

serializer.startTag("", "name");
serializer.text(depart.getName());
serializer.endTag("", "name");

serializer.startTag("", "salary");
serializer.text(depart.getSalary() + "");
serializer.endTag("", "salary");

serializer.endTag("", "person");
}
serializer.endTag("", "department");
serializer.endDocument();

return writer.toString();
}
}

布局文件activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="${packageName}.${activityClass}" >

<Button
android:id="@+id/btn_sax"
android:layout_width="300dp"
android:layout_height="150dp"
android:text="sax解析xml"
/>
<Button
android:id="@+id/btn_dom"
android:layout_width="300dp"
android:layout_height="150dp"
android:text="dom解析xml"
/>
<Button
android:id="@+id/btn_pull"
android:layout_width="300dp"
android:layout_height="150dp"
android:text="pull解析xml"
/>
<Button
android:id="@+id/btn_outxml"
android:layout_width="300dp"
android:layout_height="150dp"
android:text="输出xml"
/>

</LinearLayout>

Activity代码

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {
private static final String TAG = "XML";

private DepartParser parser;
private List<Department> departs;

private Button saxIn, domIn, pullIn, outXml;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}

private void initView() {
// TODO Auto-generated method stub
saxIn = (Button) findViewById(R.id.btn_sax);
saxIn.setOnClickListener(this);
domIn = (Button) findViewById(R.id.btn_dom);
domIn.setOnClickListener(this);
pullIn = (Button) findViewById(R.id.btn_pull);
pullIn.setOnClickListener(this);
outXml = (Button) findViewById(R.id.btn_outxml);
outXml.setOnClickListener(this);
}

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
int id = arg0.getId();
switch (id) {
case R.id.btn_sax:
saxReadXml();
break;
case R.id.btn_dom:
domReadXml();
break;
case R.id.btn_pull:
pullReadXml();
break;
case R.id.btn_outxml:
writeXml();
break;

}
}

private void saxReadXml(){
try {
InputStream is = getAssets().open("<span class="KSFIND_CLASS" id="11KSFindDIV">depart</span>s.xml");
parser = new SaxDepartmentParser(); // 创建SaxD<span class="KSFIND_CLASS" id="12KSFindDIV">epart</span>Parser实例
departs = parser.parse(is); // 解析输入流
for (Department depart : departs) {
Log.i(TAG, "sax read xml:"+depart.toString());
}
} catch (Exception e) {
Log.e(TAG, "sax read xml:"+e.getMessage());
}
}

private void domReadXml(){
try {
InputStream is = getAssets().open("<span class="KSFIND_CLASS" id="13KSFindDIV">depart</span>s.xml");
parser = new DomDepartmentParser();
departs = parser.parse(is);
for (Department depart : departs) {
Log.i(TAG, "dom read xml:"+depart.toString());
}
} catch (Exception e) {
Log.e(TAG, "dom read xml:"+e.getMessage());
}
}

private void pullReadXml(){
try {
InputStream is = getAssets().open("<span class="KSFIND_CLASS" id="14KSFindDIV">depart</span>s.xml");
parser = new PullDepartmentParser();
departs = parser.parse(is);
for (Department depart : departs) {
Log.i(TAG, "pull read xml:"+depart.toString());
}
} catch (Exception e) {
Log.e(TAG, "pull read xml:"+e.getMessage());
}
}

private void writeXml(){
try {
String xml = parser.serialize(departs);  //序列化
File dir = null;
if(Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
dir = new File(Environment.getExternalStorageDirectory()+"/xml");
if(!dir.exists()){
System.out.println("mkdirs:"+dir.mkdirs());
}
}
File file = new File(dir.getPath(), "departs.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
FileOutputStream out = new FileOutputStream(file);
out.write(xml.getBytes("UTF-8"));
out.flush();
out.close();
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}

}

输出文件在sd卡xml文件夹下，每获取一遍xml就可以输出一遍