html&xml解析之jsoup和domj4的简单使用

html&xml解析

在html和xml的解析当中，有很多包可以使用，例如dom4j,jsoup等，归根到底，他们的解析都离不开dom树，都是将其转化为一棵dom树，一个document对象来实现的。接下来是一些解析的介绍

dom4j解析，此处的方法都是来自于dom4j的文档，但是解析的过程就是这样的，不管是dom解析还是什么解析

首先获取一个document对象

public Document parse(URL url) throws DocumentException {
    SAXReader reader = new SAXReader();
    //Document document = reader.read("src/Book.xml");//把xml文档加载到document对象中
    Document document = reader.read(url);
    return document;
}

Using Iterators

获取根节点
Element root = document.getRootElement();

// iterate through child elements of root
//遍历
for ( Iterator i = root.elementIterator(); i.hasNext(); ) {
Element element = (Element) i.next();
// do something
}

// iterate through child elements of root with element name "foo"
for ( Iterator i = root.elementIterator( "foo" ); i.hasNext(); ) {
Element foo = (Element) i.next();
// do something
}

// iterate through attributes of root 
for ( Iterator i = root.attributeIterator(); i.hasNext(); ) {
Attribute attribute = (Attribute) i.next();
// do something
}

Powerful Navigation with XPath

List list = document.selectNodes( "//foo/bar" );

Node node = document.selectSingleNode( "//foo/bar/author" );

String name = node.valueOf( "@name" )

Creating a new XML document

Document document = DocumentHelper.createDocument();
Element root = document.addElement( "root" );

Element author1 = root.addElement( "author" )
.addAttribute( "name", "James" )
.addAttribute( "location", "UK" )
.addText( "James Strachan" );

Element author2 = root.addElement( "author" )
.addAttribute( "name", "Bob" )
.addAttribute( "location", "US" )
.addText( "Bob McWhirter" );

Writing a document to a file

 // lets write to a file
XMLWriter writer = new XMLWriter(
new FileWriter( "output.xml" )
);
writer.write( document );
writer.close();


// Pretty print the document to System.out
OutputFormat format = OutputFormat.createPrettyPrint();
writer = new XMLWriter( System.out, format );
writer.write( document );

// Compact format to System.out
format = OutputFormat.createCompactFormat();
writer = new XMLWriter( System.out, format );
writer.write( document );

jsoup可以抓取网上页面的功能，同时他的使用也非常的广泛，使用它可以很轻松的遍历整个文档

文档的跟多内容在这里：http://www.open-open.com/jsoup/selector-syntax.htm

//可以是这个是将String解析成为document
Document doc = Jsoup.parse(html);
//解析指定片段
Document doc = Jsoup.parseBodyFragment(html);
//你需要从一个网站获取和解析一个HTML文档
Document doc = Jsoup.connect("http://example.com/").get();
//其中还有post的请求方式，百度一下你就知道

//指定特定解码
Document doc = Jsoup.parse(input, "UTF-8", "http://example.com/");

利用jsoup解析进行深度遍历和解析，来抽取特定的内容

1. 创建一个类

   public class TagStruct {
       private Element e ;
       private int deep;
       private String xpath;
   
       public TagStruct(Element e, int deep, String xpath) {
           this.e = e;
           this.deep = deep;
           this.xpath = xpath;
       }
   }
   

解析的过程

//http://tieba.baidu.com/f?kw=c%E8%AF%AD%E8%A8%80&fr=index
Document doc = Jsoup.connect("http://tieba.baidu.com/f?kw=c%E8%AF%AD%E8%A8%80&fr=index").get();
        List list = new ArrayList();
        Stack sk  = new Stack();
        Elements allElements = doc.getAllElements();
        Element child = doc.child(0);//html标签，跟标签
        Element body = doc.body();
        doc.siblingElements();
        System.out.println(doc.getElementsByTag("a").size());
        //广度遍历
        TagStruct t = new TagStruct(body,1,"//body");
        sk.push(t);
        while (!sk.isEmpty()){
            TagStruct pop = sk.pop();
            Element e = pop.getE();
            Elements elements = e.children();

            for(int i=0;i comparator = new Comparator() {

            public int compare(TagStruct o1, TagStruct o2) {
                if(o1.getDeep()>o2.getDeep()){
                    return o1.getDeep()-o2.getDeep();
                }else {
                    return o1.getDeep()-o2.getDeep();
                }
            }
        };
        Collections.sort(list,comparator);
        //list.sort(comparator);

        for(int i=0;i