html解析
The important point about Java HTML parsing is to use a parser designed for it. While you can parse HTML using the default XML parser, it's a brittle thing because it will only accept well formed, strict XHTML.
TagSoup library
Hence, I highly recommend using the TagSoup library which slots right into the parsing framework but handles crappy HTML.
import java.net.URL;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;
import org.ccil.cowan.tagsoup.jaxp.SAXParserImpl;
public class HTMLParseExample {
public static void main(String args[]) throws Exception {
// print the 'src' attributes of <img> tags
// from http://www.yahoo.com/
// using the TagSoup parser
SAXParserImpl.newInstance(null).parse(
new URL("http://www.yahoo.com/").openConnection().getInputStream(),
new DefaultHandler() {
public void startElement(String uri, String localName,
String name, Attributes a)
{
if (name.equalsIgnoreCase("img"))
System.out.println(a.getValue("src"));
}
}
);
}
}
Xerces
And here's a slightly more complex example (collect and print the text inside nested <p> tags), this time using the standard Java XML parser Xerxes instead of TagSoup.
import java.net.URL;
import java.util.ArrayList;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.helpers.DefaultHandler;
public class XHTMLParseExample {
public static void main(String args[]) throws Exception {
// print the text in <p> ... </p> tags on http://www.w3.org/
// using the standard Java XML parser, Xerxes
javax.xml.parsers.SAXParserFactory.newInstance().newSAXParser().parse(
new URL("http://www.w3.org/").openConnection().getInputStream(),
new DefaultHandler() {
ArrayList<StringBuilder> p = new ArrayList<StringBuilder>();
public void startElement(String uri, String localName,
String name, Attributes a)
{
// push a string buffer for every <p> tag
if (name.equalsIgnoreCase("p")) {
p.add(new StringBuilder());
}
}
public void endElement(String uri, String localName, String name)
{
// pop and print a string buffer for every </p> tag
if (name.equalsIgnoreCase("p")) {
int lastIdx = p.size() - 1;
System.out.print("PARA: " + p.remove(lastIdx));
}
}
public void characters(char[] ch, int start, int length) {
// append any characters to the current string buffer
int lastIdx = p.size() - 1;
if (lastIdx > -1) {
p.get(lastIdx).append(new String(ch, start, length))
.append(' ');
}
}
// if we don't include a fake resolveEntity() method, Xerxes
// will try to download the entity URI listed its cached DTD:
// http://www.w3.org/TR/xhtml1/DTD/xhtml-lat1.ent
public InputSource resolveEntity(String publicId, String systemId)
throws org.xml.sax.SAXException, java.io.IOException
{
final String fake = "<!ENTITY nbsp \" \">";
return new InputSource(new java.io.StringReader(fake));
}
}
);
}
}