Android笔记（四十七） Android中的数据存储——XML（三）SAX解析

         SAX是一个解析速度快并且占用内存少的xml解析器，非常适合用于Android等移动设备。 SAX解析XML文件采用的是事件驱动，也就是说，它并不需要解析完整个文档，在按内容顺序解析文档的过程中，SAX会判断当前读到的字符是否合法XML语法中的某部分，如果符合就会触发事件。所谓事件，其实就是一些回调（callback）方法，这些方法(事件)定义在ContentHandler接口。下面是一些ContentHandler接口常用的方法：

startDocument()：当遇到文档的开头的时候，调用这个方法，可以在其中做一些预处理的工作。

endDocument()：和上面的方法相对应，当文档结束的时候，调用这个方法，可以在其中做一些善后的工作。

startElement(String namespaceURI, String localName, String qName, Attributes atts) ：当读到一个开始标签的时候，会触发这个方法。namespaceURI就是命名空间，localName是不带命名空间前缀的标签名，qName是带命名空间前缀的标签名。通过atts可以得到所有的属性名和相应的值。要注意的是SAX中一个重要的特点就是它的流式处理，当遇到一个标签的时候，它并不会纪录下以前所碰到的标签，也就是说，在startElement()方法中，所有你所知道的信息，就是标签的名字和属性，至于标签的嵌套结构，上层标签的名字，是否有子元属等等其它与结构相关的信息，都是不得而知的，都需要你的程序来完成。这使得SAX在编程处理上没有DOM来得那么方便。

endElement(String uri, String localName, String name)：这个方法和上面的方法相对应，在遇到结束标签的时候，调用这个方法。

characters(char[] ch, int start, int length) ：这个方法用来处理在XML文件中读到的内容，第一个参数为文件的字符串内容，后面两个参数是读到的字符串在这个数组中的起始位置和长度，使用new String(ch,start,length)就可以获取内容。

 

示例代码：

MainActivity.java

package cn.lixyz.xmltest.activity;

import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import cn.lixyz.xmltest.R;
import cn.lixyz.xmltest.model.Student;
import cn.lixyz.xmltest.parser.DOMForXML;
import cn.lixyz.xmltest.parser.PULLForXML;
import cn.lixyz.xmltest.parser.SAXForXML;

public class MainActivity extends Activity {

    private Button bt_readxml_dom, bt_writexml_dom, bt_writexml_sax, bt_readxml_sax, bt_readxml_pull, bt_writexml_pull;

    private List<Student> list;

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

        findView();
    }

    private void findView() {
        bt_readxml_dom = (Button) findViewById(R.id.bt_readxml_dom);
        bt_writexml_dom = (Button) findViewById(R.id.bt_writexml_dom);
        bt_writexml_sax = (Button) findViewById(R.id.bt_writexml_sax);
        bt_readxml_sax = (Button) findViewById(R.id.bt_readxml_sax);
        bt_readxml_pull = (Button) findViewById(R.id.bt_readxml_pull);
        bt_writexml_pull = (Button) findViewById(R.id.bt_writexml_pull);
    }

    public void clickButton(View view) {
        DOMForXML domForXML;
        SAXForXML saxForXML;
        PULLForXML pullForXML;
        switch (view.getId()) {
        case R.id.bt_readxml_dom:
            domForXML = new DOMForXML();
            domForXML.domReadXML();
            break;

        case R.id.bt_writexml_dom:
            domForXML = new DOMForXML();
            domForXML.domWriterXML();
            break;
        case R.id.bt_readxml_sax:
            saxForXML = new SAXForXML();
            saxForXML.saxReaderXML();
            break;
        case R.id.bt_writexml_sax:
            saxForXML = new SAXForXML();
            saxForXML.saxWriterXML();
            break;
        case R.id.bt_writexml_pull:
            pullForXML = new PULLForXML();
            pullForXML.pullWriterXML();
            break;
        case R.id.bt_readxml_pull:
            pullForXML = new PULLForXML();
            pullForXML.pullReaderXML();
            break;
        }
    }

}

activity_main.xml

<ScrollView 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" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="cn.lixyz.xmltest.activity.MainActivity" >

        <Button
            android:id="@+id/bt_writexml_dom"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="DOM方式生成XML" />

        <Button
            android:id="@+id/bt_readxml_dom"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="DOM方式读取XML" />

        <Button
            android:id="@+id/bt_writexml_sax"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="SAX方式生成XML" />

        <Button
            android:id="@+id/bt_readxml_sax"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="SAX方式读取XML" />

        <Button
            android:id="@+id/bt_writexml_pull"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="PULL生成XML" />

        <Button
            android:id="@+id/bt_readxml_pull"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="PULL解析XML" />
    </LinearLayout>

</ScrollView>

SAXForXML.java

package cn.lixyz.xmltest.parser;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.sax.TransformerHandler;
import javax.xml.transform.stream.StreamResult;

import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

import android.util.Log;
import cn.lixyz.xmltest.model.Student;

public class SAXForXML {

    public void saxWriterXML() {
        try {
            // 数据源
            List<Student> listData = createStudents();
            SAXTransformerFactory saxTransformerFactory = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
            TransformerHandler transformerHandler = saxTransformerFactory.newTransformerHandler();

            // 设置xml属性
            Transformer transformer = transformerHandler.getTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否缩进
            transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8"); // 字符集
            transformer.setOutputProperty(OutputKeys.VERSION, "1.0"); // 版本号

            File fileFolder = new File("data/data/cn.lixyz.xmltest/files");
            if (!fileFolder.exists()) {
                fileFolder.mkdir();
                Log.d("TTTT", "文件夹不存在，已经创建");
            }
            FileOutputStream fileOutputStream = new FileOutputStream(
                    new File("data/data/cn.lixyz.xmltest/files/studentsForSAX.xml"));

            transformerHandler.setResult(new StreamResult(fileOutputStream));

            transformerHandler.startDocument();
            AttributesImpl attributesImpl = new AttributesImpl();

            attributesImpl.clear();
            transformerHandler.startElement("", "", "students", attributesImpl);

            for (Student student : listData) {
                attributesImpl.clear();
                attributesImpl.addAttribute("", "", "id", "", student.getId() + "");
                transformerHandler.startElement("", "", "student", attributesImpl);

                attributesImpl.clear();
                transformerHandler.startElement("", "", "name", attributesImpl);
                transformerHandler.characters(student.getName().toCharArray(), 0, student.getName().length());
                ;
                transformerHandler.endElement("", "", "name");

                attributesImpl.clear();
                transformerHandler.startElement("", "", "age", attributesImpl);
                transformerHandler.characters((student.getAge() + "").toCharArray(), 0, student.getName().length());
                ;
                transformerHandler.endElement("", "", "age");

                transformerHandler.endElement("", "", "student");
            }

            transformerHandler.endElement("", "", "students");
            transformerHandler.endDocument();

        } catch (TransformerConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void saxReaderXML() {
        try {
            SAXStudentService studentService = new SAXStudentService();
            // InputStream inputStream =
            // this.getClass().getClassLoader().getResourceAsStream("person.xml");
            FileInputStream fileInputStream = new FileInputStream(
                    new File("data/data/cn.lixyz.xmltest/files/studentsForSAX.xml"));
            List<Student> students = studentService.getStudents(fileInputStream);
            for (Student student : students) {
                Log.d("TTTT", "id=" + student.getId() + ",name=" + student.getName() + ",age=" + student.getAge());
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ParserConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (Throwable e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    // 模拟生成xml的数据
    private List<Student> createStudents() {
        List<Student> listData = new ArrayList<Student>();
        listData = new ArrayList<Student>();
        Student s1 = new Student();
        s1.setId(11);
        s1.setName("张三");
        s1.setAge(10);
        listData.add(s1);
        Student s2 = new Student();
        s2.setId(22);
        s2.setName("李四");
        s2.setAge(11);
        listData.add(s2);
        Student s3 = new Student();
        s3.setId(33);
        s3.setName("王五");
        s3.setAge(12);
        listData.add(s3);
        Student s4 = new Student();
        s4.setId(44);
        s4.setName("赵六");
        s4.setAge(13);
        listData.add(s4);
        Student s5 = new Student();
        s5.setId(55);
        s5.setName("刘七");
        s5.setAge(14);
        listData.add(s5);
        return listData;
    }

}

Student.java

package cn.lixyz.xmltest.model;

public class Student {

    private int id;
    private String name;
    private int age;

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

}

SAXStudentService.java

package cn.lixyz.xmltest.parser;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

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

import android.util.Log;
import cn.lixyz.xmltest.model.Student;

public class SAXStudentService {
    public List<Student> getStudents(InputStream inputStream) throws Throwable {
        SAXParserFactory factory = SAXParserFactory.newInstance();
        SAXParser parser = factory.newSAXParser();
        StudentHandler studentHandel = new StudentHandler();
        parser.parse(inputStream, studentHandel);

        return studentHandel.getStudent();
    }

    class StudentHandler extends DefaultHandler {
        private List<Student> dataList;
        private String tag;
        private Student student;

        public List<Student> getStudent() {
            return dataList;
        }

        @Override
        public void characters(char[] ch, int start, int length) throws SAXException {
            // TODO Auto-generated method stub
            // super.characters(ch, start, length);
            if (tag != null) {
                Log.d("TTTT", "~~~~~~~");
                String str = new String(ch, start, length);
                if ("name".equals(tag)) {
                    student.setName(str);
                } else if ("age".equals(tag)) {
                    student.setAge(Integer.parseInt(str));
                }
            }
        }

        @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 ("student".equals(localName)) {
                student = new Student();
                Integer id = new Integer(attributes.getValue(0));
                student.setId(id);
            }
            tag = localName;
        }

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

        @Override
        public void endElement(String uri, String localName, String qName) throws SAXException {
            // TODO Auto-generated method stub
            // super.endElement(uri, localName, qName);

            if ("student".equals(localName)) {
                dataList.add(student);
                student = null;
            }

            tag = null;
        }
    }
}