Java Sax解析xml

客官°小女子只卖身不卖艺 2022-06-18 13:15 225阅读 0赞

Java Sax解析是按照xml文件的顺序依次来解析。

xml文件的节点分为两类，一种是ElementNode，一种是TextNode。

<?xml version="1.0" encoding="UTF-8"?>  
    <books>  
        <book id="12">  
            <name>thinking in java</name>  
            <price>85.5</price>  
        </book>  
        <book id="15">  
            <name>Spring in Action</name>  
            <price>39.0</price>  
        </book>  
    </books>

其中，<books>、<book>这种节点就属于ElementNode,而thinking in java、85.5这种就属于TextNode。

下面是代码实现：

public class Book {  
        private int id;  
        private String name;  
        private float price;  
        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 getPrice() {  
            return price;  
        }  
        public void setPrice(float price) {  
            this.price = price;  
        }  
        @Override  
        public String toString(){  
            return this.id+":"+this.name+":"+this.price;  
        }  
    }

SAX遍历解析代码

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 com.xtlh.cn.entity.Book;
    
    public class SaxParseService extends DefaultHandler{
    	private List<Book> books = null;
    	private Book book = null;
    	private String preTag = null;//作用是记录解析时的上一个节点名称
    	
    	public List<Book> getBooks(InputStream xmlStream) throws Exception{
    		SAXParserFactory factory = SAXParserFactory.newInstance();
    		SAXParser parser = factory.newSAXParser();
    		SaxParseService handler = new SaxParseService();
    		parser.parse(xmlStream, handler);
    		return handler.getBooks();
    	}
    	
    	public List<Book> getBooks(){
    		return books;
    	}
    	
    	@Override
    	public void startDocument() throws SAXException {
    		books = new ArrayList<Book>();
    	}
    
    	@Override
    	public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
    		if("book".equals(qName)){
    			book = new Book();
    			book.setId(Integer.parseInt(attributes.getValue(0)));
    		}
    		preTag = qName;//将正在解析的节点名称赋给preTag
    	}
    
    	@Override
    	public void endElement(String uri, String localName, String qName)
    			throws SAXException {
    		if("book".equals(qName)){
    			books.add(book);
    			book = null;
    		}
    		preTag = null;/**当解析结束时置为空。这里很重要，例如，当图中画3的位置结束后，会调用这个方法
    		，如果这里不把preTag置为null，根据startElement(....)方法，preTag的值还是book，当文档顺序读到图
    		中标记4的位置时，会执行characters(char[] ch, int start, int length)这个方法，而characters(....)方
    		法判断preTag!=null，会执行if判断的代码，这样就会把空值赋值给book，这不是我们想要的。*/
    	}
    	
    	@Override
    	public void characters(char[] ch, int start, int length) throws SAXException {
    		if(preTag!=null){
    			String content = new String(ch,start,length);
    			if("name".equals(preTag)){
    				book.setName(content);
    			}else if("price".equals(preTag)){
    				book.setPrice(Float.parseFloat(content));
    			}
    		}
    	}
    	
    }

测试代码

import java.io.InputStream;
    import java.util.List;
    
    import junit.framework.TestCase;
    
    import com.xtlh.cn.demo.DomParseService;
    import com.xtlh.cn.demo.SaxParseService;
    import com.xtlh.cn.entity.Book;
    
    public class ParseTest extends TestCase{
    
    	public void testSAX() throws Throwable{
    		SaxParseService sax = new SaxParseService();
    		InputStream input = this.getClass().getClassLoader().getResourceAsStream("book.xml");
    		List<Book> books = sax.getBooks(input);
    		for(Book book : books){
    			System.out.println(book.toString());
    		}
    	}
    }