android开发笔记之解析XML

前言

公司客户需求中有一个内置几个电话号码，看了一下以前工程师的代码，是采用xml文件的形式来配置几个号码，然后对应的把xml文件解析，再将这些号码插入到contacts的db数据库中。正好借这个机会，学习一下xml文件的解析。

xml解析的简单介绍

XML文件作为承载数据的一个重要角色，非常非常用户来配置和客置化，所以读写XML文件是Android开发中一项重要的技能。

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。

一个完整的Demo

我们的项目代码结构：

先在assets目录中放置一个XML文档book.xml，内容如下：

<?xml version="1.0" encoding="utf-8"?><books>    <book>        <id>1001</id>        <name>Thinking In Java</name>        <price>80.00</price>    </book>    <book>        <id>1002</id>        <name>Core Java</name>        <price>90.00</price>    </book>    <book>        <id>1003</id>        <name>Hello, Andriod</name>        <price>100.00</price>    </book></books>

再定义一个Book.java类：

package com.example.android.xml.util;public class Book {    private int id;    private String name;    private float prince;    public Book(int id, String name, float prince) {        this.id = id;        this.name = name;        this.prince = prince;    }    public Book() {    }    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 getPrince() {        return prince;    }    public void setPrince(float prince) {        this.prince = prince;    }    @Override    public String toString() {        return "Book{" +                "id=" + id +                ", name='" + name + '\'' +                ", prince=" + prince +                '}';    }}

再定义一个Util 类：

public class Util {    public static final String ITEMS = "books";    public static final String ITEM = "book";    public static final String KEY_1 = "id";    public static final String KEY_2 = "name";    public static final String KEY_3 = "price";}

最后，我们还要把这个xml文件读取的数据生成一个新的XML文档，文档路径/data/data//files/books.xml，当然查看这个路径需要userdebug或debug版本。

<?xml version="1.0" encoding="UTF-8"?>  <books>      <book id="1001">          <name>Thinking In Java</name>          <price>80.0</price>      </book>      <book id="1002">          <name>Core Java</name>          <price>90.0</price>      </book>      <book id="1003">          <name>Hello, Andriod</name>          <price>100.0</price>      </book>  </books>  

然后，我们定义一个IParse.java文件，这是一个接口，声明了一个parse方法：

import java.io.InputStream;import java.util.List;public interface IParse {    public List<Book> parse(InputStream is) throws Exception;}

然后分别实现此parse方法：

SAXParse.java 实现接口IParse，用SAX的方法解析xml文件：

import android.util.Log;import org.xml.sax.Attributes;import org.xml.sax.SAXException;import org.xml.sax.helpers.DefaultHandler;import java.io.InputStream;import java.util.ArrayList;import java.util.List;import javax.xml.parsers.SAXParser;import javax.xml.parsers.SAXParserFactory;public class SAXParse implements IParse {    public static final String TAG = "SAXParse";    @Override    public List<Book> parse(InputStream is) throws Exception {        SAXParserFactory factory = SAXParserFactory.newInstance();  //取得SAXParserFactory实例        SAXParser parser = factory.newSAXParser();                  //从factory获取SAXParser实例        MyHandler handler = new MyHandler();                        //实例化自定义Handler        parser.parse(is, handler);                                  //根据自定义Handler规则解析输入流        return handler.getBooks();    }    //需要重写DefaultHandler的方法    private class MyHandler extends DefaultHandler {        private List<Book> books;        private Book book;        private StringBuilder builder;        //返回解析后得到的Book对象集合        public List<Book> getBooks() {            return books;        }        @Override        public void startDocument() throws SAXException {            super.startDocument();            Log.i(TAG, "--------MyHandler----startDocument---------");            books = new ArrayList<Book>();            builder = new StringBuilder();        }        @Override        public void startElement(String uri, String localName, String qName, Attributes attributes)                throws SAXException {            super.startElement(uri, localName, qName, attributes);            Log.i(TAG, "--------MyHandler----startElement---------");            Log.i(TAG, "--------MyHandler----startElement---------localName:"+localName);            if (localName.equals(Util.ITEM)) {                book = new Book();            }            builder.setLength(0);   //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        }        @Override        public void characters(char[] ch, int start, int length) throws SAXException {            super.characters(ch, start, length);            Log.i(TAG, "--------MyHandler----characters---------");            Log.i(TAG, "--------MyHandler----characters---------builder:"+builder);            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 {            super.endElement(uri, localName, qName);            Log.i(TAG, "--------MyHandler----endElement---------");            Log.i(TAG, "--------MyHandler----endElement---------localName:"+localName);            Log.i(TAG, "--------MyHandler----endElement---------builder:"+builder);            if (localName.equals(Util.KEY_1)) {                book.setId(Integer.parseInt(builder.toString()));            } else if (localName.equals(Util.KEY_2)) {                book.setName(builder.toString());            } else if (localName.equals(Util.KEY_3)) {                book.setPrince(Float.parseFloat(builder.toString()));            } else if (localName.equals(Util.ITEM)) {                books.add(book);            }        }    }}

DOMParse.java 实现接口IParse，用DOM的方法解析xml文件：

import android.util.Log;import org.w3c.dom.Document;import org.w3c.dom.Element;import org.w3c.dom.Node;import org.w3c.dom.NodeList;import java.io.InputStream;import java.util.ArrayList;import java.util.List;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;public class DOMParse implements IParse {    public static final String TAG = "DOMParse";    @Override    public List<Book> parse(InputStream is) throws Exception{        List<Book> books = new ArrayList<Book>();        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();        DocumentBuilder builder = factory.newDocumentBuilder();        Document doc = builder.parse(is);        Element rootElement = doc.getDocumentElement();        NodeList items = rootElement.getElementsByTagName(Util.ITEM);        for (int i = 0; i < items.getLength(); i++) {            Book book = new Book();            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();                Log.i(TAG, "nodeName:" + nodeName);                if (nodeName.equals(Util.KEY_1)) {                    Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());                    book.setId(Integer.parseInt(property.getFirstChild().getNodeValue()));                } else if (nodeName.equals(Util.KEY_2)) {                    Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());                    book.setName(property.getFirstChild().getNodeValue());                } else if (nodeName.equals(Util.KEY_3)) {                    Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());                    book.setPrince(Float.parseFloat(property.getFirstChild().getNodeValue()));                }            }            books.add(book);        }        return books;    }}

PULLParse .java 实现接口IParse，用PULL的方法解析xml文件：

import android.util.Log;import android.util.Xml;import org.xmlpull.v1.XmlPullParser;import java.io.InputStream;import java.util.ArrayList;import java.util.List;public class PULLParse implements IParse {    public static final String TAG = "PULLParse";    @Override    public List<Book> parse(InputStream is) throws Exception {        List<Book> books = null;        Book book = null;        XmlPullParser parser = Xml.newPullParser();        parser.setInput(is, "UTF-8");        int eventType = parser.getEventType();        Log.i(TAG,"eventType:"+eventType);        while (eventType != XmlPullParser.END_DOCUMENT) {            switch (eventType) {                case XmlPullParser.START_DOCUMENT:                    Log.i(TAG,"---------------START_DOCUMENT--------------------");                    Log.i(TAG,"XmlPullParser.START_DOCUMENT");                    Log.i(TAG,"parser.getName():"+parser.getName());                    books = new ArrayList<Book>();                    break;                case XmlPullParser.START_TAG:                    Log.i(TAG,"-----------------START_TAG------------------");                    Log.i(TAG,"XmlPullParser.START_TAG");                    Log.i(TAG,"parser.getName():"+parser.getName());                    if (parser.getName().equals(Util.ITEM)) {                        book = new Book();                    } else if (parser.getName().equals(Util.KEY_1)) {                        eventType = parser.next();                        Log.i(TAG,"parser.getText():"+parser.getText());                        book.setId(Integer.parseInt(parser.getText()));                    } else if (parser.getName().equals(Util.KEY_2)) {                        eventType = parser.next();                        Log.i(TAG,"parser.getText():"+parser.getText());                        book.setName(parser.getText());                    } else if (parser.getName().equals(Util.KEY_3)) {                        eventType = parser.next();                        Log.i(TAG,"parser.getText():"+parser.getText());                        book.setPrince(Float.parseFloat(parser.getText()));                    }                    break;                case XmlPullParser.END_TAG:                    Log.i(TAG,"---------------END_TAG--------------------");                    Log.i(TAG,"XmlPullParser.END_TAG:");                    Log.i(TAG,"parser.getName():"+parser.getName());                    if (parser.getName().equals(Util.ITEM)) {                        books.add(book);                        book = null;                    }                    break;            }            eventType = parser.next();        }        return books;    }}

我们再定义一个序列化接口ISerialize，主要是把从xml文件中读取来的数据重新写到xml文件中：

import java.util.List;public interface ISerialize {    public String serialize(List<Book> books) throws Exception;}

对应的，我们再分别用三种方式来实现：

SAXSerialize.java： 用SAX的方式来实现接口ISerialize：

import android.util.Log;import org.xml.sax.helpers.AttributesImpl;import java.io.StringWriter;import java.util.List;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;public class SAXSerialize implements ISerialize {    public static final String TAG = "SAXSerialize";    @Override    public String serialize(List<Book> books) throws Exception {        //取得SAXTransformerFactory实例        SAXTransformerFactory factory = (SAXTransformerFactory) TransformerFactory.newInstance();        //从factory获取TransformerHandler实例        TransformerHandler handler = factory.newTransformerHandler();        //从handler获取Transformer实例        Transformer transformer = handler.getTransformer();        // 设置输出采用的编码方式        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");        // 是否自动添加额外的空白        transformer.setOutputProperty(OutputKeys.INDENT, "yes");        // 是否忽略XML声明        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");        StringWriter writer = new StringWriter();        Result result = new StreamResult(writer);        handler.setResult(result);        //代表命名空间的URI 当URI无值时 须置为空字符串        String uri = "";        //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        String localName = "";        handler.startDocument();        handler.startElement(uri, localName, "books", null);        //负责存放元素的属性信息        AttributesImpl attrs = new AttributesImpl();        char[] ch = null;        for (Book book : books) {            attrs.clear();  //清空属性列表            //添加一个名为id的属性(type影响不大,这里设为string)            attrs.addAttribute(uri, localName, "id", "string", String.valueOf(book.getId()));            //开始一个book元素 关联上面设定的id属性            handler.startElement(uri, localName, "book", attrs);            //开始一个name元素 没有属性            handler.startElement(uri, localName, "name", null);            ch = String.valueOf(book.getName()).toCharArray();            //设置name元素的文本节点            handler.characters(ch, 0, ch.length);            handler.endElement(uri, localName, "name");            //开始一个price元素 没有属性            handler.startElement(uri, localName, "price", null);            ch = String.valueOf(book.getPrince()).toCharArray();            //设置price元素的文本节点            handler.characters(ch, 0, ch.length);            handler.endElement(uri, localName, "price");            handler.endElement(uri, localName, "book");        }        handler.endElement(uri, localName, "books");        handler.endDocument();        Log.i(TAG, "SAXSerialize---serialize--writer.toString():"+writer.toString());        return writer.toString();    }}

DOMSerialize.java： 用DOM的方式来实现接口ISerialize：

import android.util.Log;import org.w3c.dom.Document;import org.w3c.dom.Element;import java.io.StringWriter;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;public class DOMSerialize implements ISerialize {    public static final String TAG = "DOMSerialize";    @Override    public String serialize(List<Book> books) throws Exception {        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();        DocumentBuilder builder = factory.newDocumentBuilder();        Document doc = builder.newDocument();   //由builder创建新文档        Element rootElement = doc.createElement("books");        for (Book book : books) {            Element bookElement = doc.createElement("book");            bookElement.setAttribute("id", book.getId() + "");            Element nameElement = doc.createElement("name");            nameElement.setTextContent(book.getName());            bookElement.appendChild(nameElement);            Element priceElement = doc.createElement("price");            priceElement.setTextContent(book.getPrince() + "");            bookElement.appendChild(priceElement);            rootElement.appendChild(bookElement);        }        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        Log.i(TAG, "SAXSerialize---serialize--writer.toString():" + writer.toString());        return writer.toString();    }}

PULLSerialize.java： 用PULL的方式来实现接口ISerialize：

import android.util.Log;import android.util.Xml;import org.xmlpull.v1.XmlSerializer;import java.io.StringWriter;import java.util.List;public class PULLSerialize implements ISerialize {    public static final String TAG = "PULLSerialize";    @Override    public String serialize(List<Book> books) 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("", "books");        for (Book book : books) {            serializer.startTag("", "book");            serializer.attribute("", "id", book.getId() + "");            serializer.startTag("", "name");            serializer.text(book.getName());            serializer.endTag("", "name");            serializer.startTag("", "price");            serializer.text(book.getPrince() + "");            serializer.endTag("", "price");            serializer.endTag("", "book");        }        serializer.endTag("", "books");        serializer.endDocument();        Log.i(TAG, "PULLSerialize---serialize--writer.toString():" + writer.toString());        return writer.toString();    }}

我们界面如下：

其中成局文件如下：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    app:layout_behavior="@string/appbar_scrolling_view_behavior"    tools:context="com.example.android.xml.MainActivity"    tools:showIn="@layout/activity_main">    <Button        android:id="@+id/sax_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="clickSaxParse"        android:text="sax parse xml"/>    <Button        android:id="@+id/sax_serialize"        android:layout_toRightOf="@+id/sax_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="clickSaxSerialize"        android:text="sax serialize xml"/>    <Button        android:id="@+id/dom_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_below="@id/sax_parse"        android:onClick="clickDomParse"        android:text="dom parse xml"/>    <Button        android:id="@+id/dom_serialize"        android:layout_toRightOf="@+id/dom_parse"        android:layout_alignBottom="@+id/dom_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="clickDomParseSerialize"        android:text="Dom serialize xml"/>    <Button        android:id="@+id/pull_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_below="@id/dom_parse"        android:onClick="clickPullParse"        android:text="pull parse xml"/>    <Button        android:id="@+id/pull_serialize"        android:layout_toRightOf="@+id/pull_parse"        android:layout_alignBottom="@+id/pull_parse"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="clickPullParseSerialize"        android:text="pull serialize xml"/></RelativeLayout>

然后在activity中实现的逻辑如下：

import android.content.Context;import android.os.Bundle;import android.support.design.widget.FloatingActionButton;import android.support.design.widget.Snackbar;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.util.Log;import android.view.View;import com.example.android.xml.util.Book;import com.example.android.xml.util.DOMParse;import com.example.android.xml.util.DOMSerialize;import com.example.android.xml.util.IParse;import com.example.android.xml.util.ISerialize;import com.example.android.xml.util.PULLParse;import com.example.android.xml.util.PULLSerialize;import com.example.android.xml.util.SAXParse;import com.example.android.xml.util.SAXSerialize;import java.io.FileOutputStream;import java.io.InputStream;import java.util.List;public class MainActivity extends AppCompatActivity {    public final static String TAG ="MainActivity";    private IParse parse;    private ISerialize serialize;    private List<Book> books = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)                        .setAction("Action", null).show();            }        });    }    public void clickSaxParse(View view){        Log.i(TAG, "clickSaxParse");        try {            InputStream is = getAssets().open("book.xml");            parse = new SAXParse();//          parse = new DomParser();//          parse = new PULLParse();            books = parse.parse(is);        } catch (Exception e) {            e.printStackTrace();        }        printBooks();    }    public void clickDomParse(View view){        Log.i(TAG,"clickDomParse");        try {            InputStream is = getAssets().open("book.xml");//          parse = new SAXParser();            parse = new DOMParse();//          parse = new PULLParse();            books = parse.parse(is);        } catch (Exception e) {            e.printStackTrace();        }        printBooks();    }    public void clickPullParse(View view){        Log.i(TAG,"clickPullParse");        try {            InputStream is = getAssets().open("book.xml");//          parse = new SAXParser();//          parse = new DomParser();            parse = new PULLParse();            books = parse.parse(is);        } catch (Exception e) {            e.printStackTrace();        }        printBooks();    }    public void clickSaxSerialize(View view){        Log.i(TAG, "clickSaxSerialize");        try {            serialize = new SAXSerialize();            //序列化            String xml = serialize.serialize(books);            FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);            fos.write(xml.getBytes("UTF-8"));        } catch (Exception e) {            Log.e(TAG, e.getMessage());        }    }    public void clickDomParseSerialize(View view){        Log.i(TAG,"clickDomParseSerialize");        try {            serialize = new DOMSerialize();            //序列化            String xml = serialize.serialize(books);            FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);            fos.write(xml.getBytes("UTF-8"));        } catch (Exception e) {            Log.e(TAG, e.getMessage());        }    }    public void clickPullParseSerialize(View view){        Log.i(TAG, "clickPullParseSerialize");        try {            serialize = new PULLSerialize();            //序列化            String xml = serialize.serialize(books);            FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);            fos.write(xml.getBytes("UTF-8"));        } catch (Exception e) {            Log.e(TAG, e.getMessage());        }    }    public void printBooks(){        for (Book book : books) {            Log.i(TAG, book.toString());        }    }}

总结

对于这三种解析器各有优点，因为SAX解析器操作起来太笨重，DOM不适合文档较大，内存较小的场景，唯有PULL轻巧灵活，速度快，占用内存小，使用非常顺手，所以android开发推荐PULL解析器。

参考资料

(1) Android中解析XML
http://blog.csdn.net/liuhe688/article/details/6415593
(2)【Android】实现XML解析的几种技术
http://www.cnblogs.com/weixing/archive/2013/08/07/3243366.html