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