XML file parsing summary SAX/DOM/PULL detailed introduction

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Sax features (SAX is Simple API for XML abbreviation)

1. High parsing efficiency and small memory usage

2. You can stop parsing at any time

3. Unable to load the entire document into memory

4. Unable to write xml

5. SAX uses the event driver## to parse xml files.

#The difference between pull and sax

1. After pull reads the xml file, it triggers the corresponding event and calls the method to return a number.

2.pull can be controlled in the program, and you can stop wherever you want to parse it

3.

It is more recommended to use pull parsing in Android

DOM Features

Advantages

1. The entire

document tree is in memory, easy to operate; supports deletion, modification, rearrangement, etc. Function

2. Access xml documents through tree structure

3. You can move forward or backward on a node of the tree

Disadvantages

1. Transfer the entire document into memory (including useless nodes), which wastes time and space

Applicable occasions

Once the document is parsed, the data needs to be accessed multiple times; hardware resources Sufficient (memory, cpu)

First define I define a Student.xml file

**Example**

[code]<?xml version="1.0" encoding="utf-8"?>
<students>

    <student id="1" >

        <name>
小红
        </name>

        <age>
21
        </age>

        <sex>
女
        </sex>

        <adress>
上海
        </adress>
    </student>

    <student id="2" >

        <name>
小黑
        </name>

        <age>
22
        </age>

        <sex>
男
        </sex>

        <adress>
天津
        </adress>
    </student>

    <student id="3" >

        <name>
小网
        </name>

        <age>
23
        </age>

        <sex>
男
        </sex>

        <adress>
北京
        </adress>
    </student>

</students>

**1.sax parsing* *

[code]package com.example.sax_xml;

import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;

import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void sax_xml(View v) {
        // 得到设备管理者对象
        AssetManager manager = this.getAssets();
        try {
            // 获取到assets目录下的Student.xml文件输入流
            InputStream is = manager.open("Student.xml");
            /**
             * SAXParserFactory 定义了一个API工厂，使得应用程序可以配置和获得一个基于SAX（Simple API for
             * XML
             * 
             * ）的解析器，从而能够解析XML文档( 原文： Defines a factory API that enables
             * applications to configure and obtain a SAX based parser to parse
             * XML documents. )
             * 
             * 它的构造器是受保护的，因而只能用newInstance（）方法获得实例（ Protected constructor to
             * force use of newInstance(). ）
             */
            SAXParserFactory factory = SAXParserFactory.newInstance();

            /**
             * XmlReader 类是一个提供对 XML 数据的非缓存、只进只读访问的抽象基类。 该类符合 W3C 可扩展标记语言 (XML)
             * 1.0 和 XML 中的命名空间的建议。 XmlReader 类支持从流或文件读取 XML 数据。
             * 该类定义的方法和属性使您可以浏览数据并读取节点的内容。 当前节点指读取器所处的节点。
             * 使用任何返回当前节点值的读取方法和属性推进读取器。 XmlReader 类使您可以： 1. 检查字符是不是合法的
             * XML字符，元素和属性的名称是不是有效的 XML 名称。 2. 检查 XML 文档的格式是否正确。 3. 根据 DTD
             * 或架构验证数据。 4.从 XML流检索数据或使用提取模型跳过不需要的记录。
             */
            XMLReader xmlReader = factory.newSAXParser().getXMLReader();
            /**
             * ContentHandler是Java类包中一个特殊的SAX接口，位于org.xml.sax包中。该接口封装了一些对事件处理的方法
             * ，当XML解析器开始解析XML输入文档时，它会遇到某些特殊的事件，比如文档的开头和结束、元素开头和结束、以及元素中的字符数据等事件
             * 。当遇到这些事件时，XML解析器会调用ContentHandler接口中相应的方法来响应该事件。
             */
            //由于它是一个接口所以我直接编写一个类继承它的子类DefaultHandler，重新其方法
            ContentHandler handler = new ContentHandler();
            // 将ContentHandler的实例设置到XMLReader中
            // setContentHandler此方法设置 XML 读取器的内容处理程序
            xmlReader.setContentHandler(handler);
            // 开始执行解析
            //InputSource：XML 实体的单一输入源。
            xmlReader.parse(new InputSource(is));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

**Self-defined ContentHandler class**

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

import android.util.Log;

public class ContentHandler extends DefaultHandler {

    private StringBuilder id;
    private StringBuilder name;
    private StringBuilder sex;
    private StringBuilder age;
    private StringBuilder adress;
    private String nodeName;// 记录当前节点的名字

    // 开始xml解析的时候调用
    @Override
    public void startDocument() throws SAXException {
        id = new StringBuilder();
        name = new StringBuilder();
        sex = new StringBuilder();
        age = new StringBuilder();
        adress = new StringBuilder();
    }

    // 开始解析某个节点的时候调用
    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes attributes) throws SAXException {
        nodeName = localName;
    }

    // 获取某个节点中的内容时调用
    @Override
    public void characters(char[] ch, int start, int length)
            throws SAXException {
        if ("id".equals(nodeName)) {
            id.append(ch, start, length);
        } else if ("name".equals(nodeName)) {
            name.append(ch, start, length);
        } else if ("age".equals(nodeName)) {
            age.append(ch, start, length);
        } else if ("sex".equals(nodeName)) {
            sex.append(ch, start, length);
        } else if ("adress".equals(nodeName)) {
            adress.append(ch, start, length);
        }
    }

    //完成某个节点的解析的时候调用
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        if ("student".equals(localName)) {
            Log.d("ContentHandler", "id is" + id.toString().trim());
            Log.d("ContentHandler", "name is" + name.toString().trim());
            Log.d("ContentHandler", "age is" + age.toString().trim());
            Log.d("ContentHandler", "sex is" + sex.toString().trim());
            Log.d("ContentHandler", "adress is" + adress.toString().trim());
            // 最后要将StringBuilder清空掉
            id.setLength(0);
            name.setLength(0);
            age.setLength(0);
            sex.setLength(0);
            adress.setLength(0);
        }
    }

    //完成整个XML解析的时候调用
    @Override
    public void endDocument() throws SAXException {
        // TODO Auto-generated method stub
        super.endDocument();
    }
}

**2.pull analysis**

[code]package com.example.xmlpull;

import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.util.Log;
import android.util.Xml;
import android.view.View;
import android.widget.Toast;

import org.xmlpull.v1.XmlPullParser;

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

/**
 * 
 *         读取到xml的声明返回数字0 START_DOCUMENT; 
 *         读取到xml的结束返回数字1 END_DOCUMENT ;
 *         读取到xml的开始标签返回数字2 START_TAG 
 *         读取到xml的结束标签返回数字3 END_TAG 
 *         读取到xml的文本返回数字4  TEXT
 * 
 */
public class MainActivity extends Activity {
    /**
     * 用于装载解析出来的数据
     */
    private List<Map<String, Object>> oList;
    private Map<String, Object> oMap;

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

    }

    public void btn_pull(View v) {
        // 获取设备管理器对象
        AssetManager manager = this.getAssets();
        try {
            // 得到assets文件下的Student.xml文件输入流
            InputStream is = manager.open("Student.xml");
            // 得到pull解析对象,它的构造器是受保护的，因而只能用newInstance（）方法获得实例
            XmlPullParser parser = Xml.newPullParser();
            // 将xml文件输入流传给pull解析对象
            parser.setInput(is, "UTF-8");
            // 获取解析时的事件类型,
            int type = parser.getEventType();
            // 使用while循环，如果解析的事件类型不等于全文档最后节点类型，一直解析
            while (type != XmlPullParser.END_DOCUMENT) {
                // 得到当前的节点名字
                String nodeName = parser.getName();
                switch (type) {
                // 如果是全文档的开始节点类型
                case XmlPullParser.START_DOCUMENT:
                    // 初始化装载数据的集合
                    oList = new ArrayList<Map<String, Object>>();
                    break;

                // 如果是group开始节点类型
                case XmlPullParser.START_TAG:
                    // 根据解析的节点名字进行判断
                    if ("students".equals(nodeName)) {

                    } else if ("student".equals(nodeName)) {
                        oMap = new HashMap<String, Object>();
                        // 得到group开头的student节点
                        String id = parser.getAttributeValue(0);
                        oMap.put("id", id);
                    } else if ("name".equals(nodeName)) {
                        // 节点对应的文本
                        String name = parser.nextText();
                        oMap.put("name", name);
                    } else if ("sex".equals(nodeName)) {
                        String sex = parser.nextText();
                        oMap.put("sex", sex);
                    } else if ("age".equals(nodeName)) {
                        String age = parser.nextText();
                        oMap.put("age", age);
                    } else if ("adress".equals(nodeName)) {
                        String adress = parser.nextText();
                        oMap.put("adress", adress);
                    }
                    break;

                // 到了group最后的节点
                case XmlPullParser.END_TAG:
                    if ("name".equals(nodeName)) {
                        Toast.makeText(this, "姓名解析完成", Toast.LENGTH_LONG)
                                .show();
                    }
                    if ("student".equals(nodeName)) {
                        oList.add(oMap);
                    }
                    break;
                }

                //切换到下一个group
                type = parser.next();

            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        //最后遍历集合Log
        for (int i = 0; i < oList.size(); i++) {

            Log.e("error",
                    "name:" + oList.get(i).get("name") + "----sex:"
                            + oList.get(i).get("sex") + "----age:"
                            + oList.get(i).get("age") + "----address:"
                            + oList.get(i).get("adress"));
        }

    }

}

First let’s talk about DOM analysis Things that need to be noted, because our teacher made this mistake when talking about this, here is a special point out

Here when we get the node student, that is, in the figure Where the arrow is drawn, if we call its getChildNodes() method, guess how many child nodes it has? It does not include its grandson nodes, except for Xiaohong, because it is a grandson node. It has a total of 5 child nodes, which are marked by the black horizontal lines in the figure. So when parsing, be careful not to ignore white spaces.

The specific parsing code is attached below

Here I split the dom parsing part into a tool class

[code]package com.example.domxml;

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

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 *Dom解析是将xml文件全部载入，组装成一颗dom树，
 *然后通过节点以及节点之间的关系来解析xml文件,一层一层拨开
 */
public class Dom_xml_Util {
    private List<Student> list = new ArrayList<Student>();  
    public List<Student> getStudents(InputStream in) throws Exception{
        //获取dom解析工厂，它的构造器是受保护的，因而只能用newInstance（）方法获得实例
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        //使用当前配置的参数创建一个新的 DocumentBuilder 实例
        //DocumentBuilder使其从 XML 文档获取 DOM 文档实例。
        //使用此类，应用程序员可以从 XML 获取一个 Document
        DocumentBuilder builder = factory.newDocumentBuilder();  
        //获取Document
        Document document = builder.parse(in); 
        //getDocumentElement()这是一种便捷属性，该属性允许直接访问文档的文档元素的子节点
        //Element 接口表示 HTML 或 XML 文档中的一个元素
        Element element = document.getDocumentElement();  
        //以文档顺序返回具有给定标记名称的所有后代 Elements 的 NodeList
        NodeList bookNodes = element.getElementsByTagName("student"); 
        //遍历NodeList
        //getLength()列表中的节点数
        for(int i=0;i<bookNodes.getLength();i++){  
            //返回集合中的第 i个项
            Element bookElement = (Element) bookNodes.item(i);  
            Student student = new Student();  
            //得到item大节点中的属性值。
            student.setId(Integer.parseInt(bookElement.getAttribute("id"))); 
            //得到大节点中的小节点的Nodelist
            NodeList childNodes = bookElement.getChildNodes();  
//          System.out.println("*****"+childNodes.getLength());  
            //遍历小节点
            for(int j=0;j<childNodes.getLength();j++){  
                /**
                 * getNodeType()表示基础对象的类型的节点
                 * Node.ELEMENT_NODE  该节点为 Element
                 * getNodeName()此节点的名称，取决于其类型
                 * getFirstChild() 此节点的第一个子节点
                 * getNodeValue()此节点的值，取决于其类型
                 */
                if(childNodes.item(j).getNodeType()==Node.ELEMENT_NODE){  
                    if("name".equals(childNodes.item(j).getNodeName())){  
                        student.setName(childNodes.item(j).getFirstChild().getNodeValue());  
                    }else if("age".equals(childNodes.item(j).getNodeName())){  
                        student.setAge(Integer.parseInt(childNodes.item(j).getFirstChild().getNodeValue()));  
                    }else if("sex".equals(childNodes.item(j).getNodeName())){  
                        student.setSex(childNodes.item(j).getFirstChild().getNodeValue());  
                    }else if("address".equals(childNodes.item(j).getNodeName())){  
                        student.setAddress(childNodes.item(j).getFirstChild().getNodeValue());  
                    }  
                }  
            }//end for j  
            list.add(student);  
        }//end for i  
        return list;
    }
}

Student.class

[code]package com.example.domxml;

public class Student {

    private int id;
    private String name;
    private int age;
    private String sex;
    private String address;
    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;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }

}

Call in activity

activity_main

[code]<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" >

    <TextView
        android:id="@+id/tv_id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
     <TextView
        android:id="@+id/tv_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
      <TextView
        android:id="@+id/tv_age"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
       <TextView
        android:id="@+id/tv_sex"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
        <TextView
        android:id="@+id/tv_adress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

MainActivity

[code]package com.example.domxml;

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

import android.os.Bundle;
import android.app.Activity;
import android.content.res.AssetManager;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends Activity {

    private TextView tv_id,tv_name,tv_age,tv_sex,tv_adress;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_id=(TextView)findViewById(R.id.tv_id);
        tv_name=(TextView)findViewById(R.id.tv_name);
        tv_age=(TextView)findViewById(R.id.tv_age);
        tv_sex=(TextView)findViewById(R.id.tv_sex);
        tv_adress=(TextView)findViewById(R.id.tv_adress);
    }
    public void bnt_parse(View v) 
    {
        AssetManager manager=getAssets();
        try {
            InputStream in=manager.open("Student.xml");
            List<Student> oList =new ArrayList<Student>();
            try {
                //返回一个泛型为Student的集合
                oList = new Dom_xml_Util().getStudents(in);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            //遍历集合，取集合中的第一组数据
            for (int i = 0; i < oList.size(); i++) {
                tv_id.setText(oList.get(0).getId());
                tv_name.setText(oList.get(0).getName());
                tv_age.setText(oList.get(0).getAge());
                tv_sex.setText(oList.get(0).getSex());
                tv_adress.setText(oList.get(0).getAddress());
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

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