在Android中,常見的XML解析器分别為SAX解析器、DOM解析器和PULL解析器
SAX解析器:
SAX(Simple API for XML)解析器是一種基于事件的解析器,它的核心是事件處理模式,主要是圍繞着事件源以及事件處理器來工作的。當事件源産生事件後,調用事件處理器相應的處理方法,一個事件就可以得到處理。在事件源調用事件處理器中特定方法的時候,還要傳遞給事件處理器相應事件的狀态資訊,這樣事件處理器才能夠根據提供的事件資訊來決定自己的行為。
SAX解析器的優點是解析速度快,占用記憶體少。非常适合在Android移動裝置中使用。
DOM解析器:
DOM是基于樹形結構的的節點或資訊片段的集合,允許開發人員使用DOM API周遊XML樹、檢索所需資料。分析該結構通常需要加載整個文檔和構造樹形結構,然後才可以檢索和更新節點資訊。
由于DOM在記憶體中以樹形結構存放,是以檢索和更新效率會更高。但是對于特别大的文檔,解析和加載整個文檔将會很耗資源。
PULL解析器:
PULL解析器的運作方式和SAX類似,都是基于事件的模式。不同的是,在PULL解析過程中,我們需要自己擷取産生的事件然後做相應的操作,而不像SAX那樣由處理器觸發一種事件的方法,執行我們的代碼。PULL解析器小巧輕便,解析速度快,簡單易用,非常适合在Android移動裝置中使用,Android系統内部在解析各種XML時也是用PULL解析器。
下面我們做一個demo來具體實作下
首先在Androidmanifest.xml中添權重限,此權限用于輸出xml檔案
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
departments.xml被解析的xml檔案
<?xml version="1.0" encoding="utf-8"?>
<department>
<person>
<id>1001</id>
<name>張三</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>
封裝實體類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;
}
}
為解析器定義一個DepartParser接口,每種類型的解析器需要實作此接口
public interface DepartParser {
/**
* 解析輸入流 得到Department對象集合
* @param is
* @return
* @throws Exception
*/
public List<Department> parse(InputStream is) throws Exception;
/**
* 序列化Department對象集合,得到XML形式的字元串
* @param departs
* @return
* @throws Exception
*/
public String serialize(List<Department> departs) throws Exception;
}
serialize(List<Department>)解析出來的資料樣式如下:
<?xml version="1.0" encoding="utf-8"?>
<department>
<person id="1001">
<name>張三</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執行個體
SAXParserFactory factory = SAXParserFactory.newInstance();
// 從factory擷取SAXParser執行個體
SAXParser parser = factory.newSAXParser();
// 執行個體化自定義Handler
MyHandler handler = new MyHandler();
// 根據自定義Handler規則解析輸入流
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(); // 從factory擷取TransformerHandler執行個體
Transformer transformer = handler.getTransformer(); // 從handler擷取Transformer執行個體
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // 設定輸出采用的編碼方式
transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否自動添加額外的空白
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // 是否忽略XML聲明
StringWriter writer = new StringWriter();
//Result result = new StreamResult();這樣的話,handler.startDocument()會報 No output specified異常
Result result = new StreamResult(writer);
handler.setResult(result);
String uri = "";//代表命名空間的URI 當URI無值時 須置為空字元串
String localName = "";//命名空間的本地名稱(不包含字首) 當沒有進行命名空間處理時 須置為空字元串
handler.startDocument();
handler.startElement(uri, localName, "department", null);
AttributesImpl attrs = new AttributesImpl(); //負責存放元素的屬性資訊
char[] ch = null;
for (Department depart : departs) {
attrs.clear(); //清空屬性清單
attrs.addAttribute(uri, localName, "id", "string", String.valueOf(depart.getId()));//添加一個名為id的屬性(type影響不大,這裡設為string)
handler.startElement(uri, localName, "person", attrs); //開始一個元素 關聯上面設定的id屬性
handler.startElement(uri, localName, "name", null); //開始一個name元素 沒有屬性
ch = String.valueOf(depart.getName()).toCharArray();
handler.characters(ch, 0, ch.length); //設定name元素的文本節點
handler.endElement(uri, localName, "name");
handler.startElement(uri, localName, "salary", null);//開始一個price元素 沒有屬性
ch = String.valueOf(depart.getSalary()).toCharArray();
handler.characters(ch, 0, ch.length); //設定price元素的文本節點
handler.endElement(uri, localName, "salary");
handler.endElement(uri, localName, "person");
}
handler.endElement(uri, localName, "department");
handler.endDocument();
return writer.toString();
}
/**
* DefaultHandler是一個事件處理器,可以接收解析器報告的所有事件,處理所發現的資料
*
* @author 孟祥程
*
*/
private class MyHandler extends DefaultHandler {
private List<Department> departs;
private Department depart;
private StringBuilder builder;
// 傳回解析後得到的<span class="KSFIND_CLASS" id="2KSFindDIV">Department</span>對象集合
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();
}
// 将字元長度設定為0 以便重新開始讀取元素内的字元節點
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);
// 将讀取的字元數組追加到builder中
builder.append(ch, start, length);//将讀取的字元數組追加到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執行個體
DocumentBuilder builder = factory.newDocumentBuilder(); //從factory擷取DocumentBuilder執行個體
Document doc = builder.parse(is); //解析輸入流 得到Document執行個體
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建立新文檔
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執行個體
Transformer transformer = transFactory.newTransformer(); //從transFactory擷取Transformer執行個體
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // 設定輸出采用的編碼方式
transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否自動添加額外的空白
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // 是否忽略XML聲明
StringWriter writer = new StringWriter();
Source source = new DOMSource(doc); //表明文檔來源是doc
Result result = new StreamResult(writer);//表明目标結果為writer
transformer.transform(source, result); //開始轉換
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建立一個XmlPullParser執行個體
parser.setInput(is, "UTF-8"); //設定輸入流 并指明編碼方式
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建立一個XmlSerializer執行個體
StringWriter writer = new StringWriter();
serializer.setOutput(writer); //設定輸出方向為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();
}
}
布局檔案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="輸出xml"
/>
</LinearLayout>
Activity代碼
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(); // 建立SaxD<span class="KSFIND_CLASS" id="12KSFindDIV">epart</span>Parser執行個體
departs = parser.parse(is); // 解析輸入流
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());
}
}
}
輸出檔案在sd卡xml檔案夾下,每擷取一遍xml就可以輸出一遍