android学习笔记(02)-Sax解析XML与JSON的解析

Sax解析
--------------

1.解析方式:边读边解析

2.读到特定标签的时候，自动调用相应的方法进行操作

3.不会造成内存的溢出

4.不能修改xml文件

　　

Sax解析

 

//SaxParserTest.java

import java.util.ArrayList;

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

import org.junit.Test;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

import com.hzg.xmlParse.bean.Book;

public class SaxParserTest {
    @Test
    public void saxParser() throws Exception{
        //获取工厂
        SAXParserFactory parserFactory = SAXParserFactory.newInstance();
        SAXParser saxParser = parserFactory.newSAXParser();
        //获取xmlReader通过reader可以试着ContentHandler
        XMLReader xmlReader = saxParser.getXMLReader();
        //给xmlRead设置contentHandler contentHandler是一个接口里面太多的方法没实现
        //不去直接实现contentHandler而是继承他的默认的实现DefaultHandler
        xmlReader.setContentHandler(new MyHandler());
        xmlReader.parse("Books.xml");
        
        
    }
    
    private class MyHandler extends DefaultHandler{

        @Override
        public void characters(char[] ch, int start, int length) throws SAXException {
            String text = new String(ch, start, length);
            System.out.println("文本内容"+text);
        }

        @Override
        public void endDocument() throws SAXException {
            System.out.println("wendangjieshu");
        }

        @Override
        public void endElement(String uri, String localName, String qName) throws SAXException {
            System.out.println("jieshu标签<"+ qName +">");
        }

        @Override
        public void startDocument() throws SAXException {
            System.out.println("wendangkaishi");
        }

        @Override
        public void startElement(String uri, String localName, String qName, Attributes attributes)
                throws SAXException {
            System.out.println("开始标签<"+ qName +">");
            
        }
        
    }
    
    
    //获取第二本书的售价
    @Test
    public void saxParserTest2() throws Exception{
        SAXParserFactory parserFactory = SAXParserFactory.newInstance();
        SAXParser parser = parserFactory.newSAXParser();
        XMLReader reader = parser.getXMLReader();
        reader.setContentHandler(new DefaultHandler(){
            boolean isPrice = false;
            int count = 0;
            @Override
            public void characters(char[] ch, int start, int length) throws SAXException {
                if(isPrice && count == 2){
                    System.out.println(new String(ch, start, length));
                }
            }

            @Override
            public void endElement(String uri, String localName, String qName) throws SAXException {
                if("example:售价".equals(qName)){
                    isPrice = false;
                }
            }

            @Override
            public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
                if("example:售价".equals(qName)){
                    isPrice = true;
                    count++;
                }
            }
            
        });
        reader.parse("Books.xml");
    
    }
    
    //生成集合
    @Test
    public void saxParse2list() throws Exception{
        SAXParserFactory parserFactory = SAXParserFactory.newInstance();
        SAXParser parser = parserFactory.newSAXParser();
        XMLReader reader = parser.getXMLReader();
        reader.setContentHandler(new DefaultHandler(){
            ArrayList<Book> bookshelf = null;
            Book book = null;
            String tag = null;
            @Override
            public void characters(char[] ch, int start, int length) throws SAXException {
                if("example:书名".equals(tag)){
                    book.setTitle(new String(ch,start,length));
                }else if("example:作者".equals(tag)){
                    book.setAuthor(new String(ch,start,length));
                }else if("example:售价".equals(tag)){
                    book.setPrice(new String(ch,start,length));
                }
            }

            @Override
            public void endElement(String uri, String localName, String qName) throws SAXException {
                //每次标签结束把tag设置为null
                tag = null;
                if("example:书架".equals(qName)){
                    for(Book book1:bookshelf){
                        System.out.println(book1);
                    }
                }else if("example:书".equals(qName)){
                    //读到书的结束标签 把book对象添加到集合中
                    bookshelf.add(book);
                }
            }

            @Override
            public void startElement(String uri, String localName, String qName, Attributes attributes)
                    throws SAXException {
                if("example:书架".equals(qName)){
                    //创建集合
                    bookshelf = new ArrayList<Book>();
                }else if("example:书".equals(qName)){
                    //创建对象
                    book = new Book();
                }else if("example:书名".equals(qName)){
                    tag = "example:书名";
                }else if("example:作者".equals(qName)){
                    tag = "example:作者";
                }else if("example:售价".equals(qName)){
                    tag = "example:售价";
                }
            }
            
        });
        reader.parse("Books.xml");
        
    }
}

//Book.java

public class Book {
    private String title;
    private String author;
    private String price;
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
    public String getPrice() {
        return price;
    }
    public void setPrice(String price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Book [title=" + title + ", author=" + author + ", price=" + price + "]";
    }
    
    
}

JSON(JavaScript Object Notation)
--------------
JavaScript对象表示法
规则:
1.映射用冒号(":")表示。名称:值
2.并列的数据之间用(",")分隔。名称1:值1,名称2:值2
3.映射的集合(对象)用大括号("{}")表示。{名称1:值1,名称2:值2}
4.并列的集合(数组)用方括号("[]")表示。
[
{名称1:值1,名称2:值2}
{名称1:值1,名称2:值2}
]
5.元素值可具有的类型:string, number, object, array, true, false, null

JSON的解析
--------------
org.json, json-lib, gson

org.json解析JSON
--------------
官网:http:www.json.org/java/
常见API:

//将json字符串转换成JSONObject对象
JSONObject jb = new JSONObject(String source);
Object get(String key);
int getInt(String key);
String getString(String key);
XXX getXXX(String key);
JSONArray getJSONArray(String key);

//将json字符串转成JSONArray对象
 JSONArray jsArray = new JSONArray(String source); 

JSON解析示例:

import org.json.*;

public class JsonParseDemo {
    
    public  static void main(String [] args) throws Exception{
        jsonTest();
    }
    
    public static void jsonTest() throws Exception{
        //
        String jstring = "{'name':'是否','age':'20'}";
        //通过一个具有json格式的字符串可以创建一个json对象
        JSONObject obj = new JSONObject(jstring);
        //获取json对象之后就可以通过key去取值
        String name = obj.getString("name");
        int age = obj.getInt("age");
        System.out.println("名字"+name+"age"+age);
        
        
        //遍历name
        String jsonArray = "[{'name':'是否','age':'20'},{'name':'adf','age':'25'}]";
        //根据一个具有json数组格式的字符串创建一个json数组对象
        JSONArray array = new JSONArray(jsonArray);
        for(int i = 0; i< array.length();i++){
            //根据索引取出每一个jsonobject
            JSONObject jsonObject = array.getJSONObject(i);
            //
            name = jsonObject.getString("name");
            System.out.println(name);
        }
        
    }
}