Reading website's contents into string

问题:

Currently I'm working on a class that can be used to read the contents of the website specified by the url. I'm just beginning my adventures with java.io and java.net so I need to consult my design.

Usage:

TextURL url = new TextURL(urlString);
String contents = url.read();

My code:

package pl.maciejziarko.util;

import java.io.*;
import java.net.*;

public final class TextURL
{
    private static final int BUFFER_SIZE = 1024 * 10;
    private static final int ZERO = 0;
    private final byte[] dataBuffer = new byte[BUFFER_SIZE];
    private final URL urlObject;

    public TextURL(String urlString) throws MalformedURLException
    {
        this.urlObject = new URL(urlString);
    }

    public String read() 
    {
        final StringBuilder sb = new StringBuilder();

        try
        {
            final BufferedInputStream in =
                    new BufferedInputStream(urlObject.openStream());

            int bytesRead = ZERO;

            while ((bytesRead = in.read(dataBuffer, ZERO, BUFFER_SIZE)) >= ZERO)
            {
                sb.append(new String(dataBuffer, ZERO, bytesRead));
            }
        }
        catch (UnknownHostException e)
        {
            return null;
        }
        catch (IOException e)
        {
            return null;
        }

        return sb.toString();
    }

    //Usage:
    public static void main(String[] args)
    {
        try
        {
            TextURL url = new TextURL("http://www.flickr.com/explore/interesting/7days/");
            String contents = url.read();

            if (contents != null)
                System.out.println(contents);
            else
                System.out.println("ERROR!");
        }
        catch (MalformedURLException e)
        {
            System.out.println("Check you the url!");
        }
    }
}

My question is: Is it a good way to achieve what I want? Are there any better solutions?

I particularly didn't like sb.append(new String(dataBuffer, ZERO, bytesRead)); but I wasn't able to express it in a different way. Is it good to create a new String every iteration? I suppose no.

Any other weak points?

Thanks in advance!

回答1:

Consider using URLConnection instead. Furthermore you might want to leverage IOUtils from Apache Commons IO to make the string reading easier too. For example:

URL url = new URL("http://www.example.com/");
URLConnection con = url.openConnection();
InputStream in = con.getInputStream();
String encoding = con.getContentEncoding();  // ** WRONG: should use "con.getContentType()" instead but it returns something like "text/html; charset=UTF-8" so this value must be parsed to extract the actual encoding
encoding = encoding == null ? "UTF-8" : encoding;
String body = IOUtils.toString(in, encoding);
System.out.println(body);

If you don't want to use IOUtils I'd probably rewrite that line above something like:

ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[8192];
int len = 0;
while ((len = in.read(buf)) != -1) {
    baos.write(buf, 0, len);
}
String body = new String(baos.toByteArray(), encoding);

回答2:

I highly recommend using a dedicated library, like HtmlParser:

Parser parser = new Parser (url);
NodeList list = parser.parse (null);
System.out.println (list.toHtml ());

Writing your own html parser is such a loose of time. Here is its maven dependency. Look at its JavaDoc for digging into its features.

Looking at the following sample should be convincing:

Parser parser = new Parser(url);
NodeList movies = parser.extractAllNodesThatMatch(
    new AndFilter(new TagNameFilter("div"),
    new HasAttributeFilter("class", "movie")));

回答3:

Unless this is some sort of exercise that you want to code for the sake of learning ... I would not reinvent the wheel and I would use HttpURLConnection.

HttpURLConnection provides good encapsulation mechanisms to deal with the HTTP protocol. For instance, your code doesn't work with HTTP redirections, HttpURLConnection would fix that for you.

回答4:

You can wrap your InputStream in a InputStreamReader and can use it's read() method to read character data directly (note that you should specify the encoding when creating the Reader, but finding out the encoding of arbitrary URLs is non-trivial). Then simply call sb.append() with the char[] you just read (and the correct offset and length).

回答5:

Hey Please use these lines of codes , it will help u..

 <!DOCTYPE html>
    <html>
        <head>
            <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
            <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
            <title>JSP Page</title>

        </head>
        <body>
            <h1>Hello World!</h1> 






        URL uri= new URL("Your url");
        URLConnection ec = uri.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(
                ec.getInputStream(), "UTF-8"));
        String inputLine;
        StringBuilder a = new StringBuilder();
        while ((inputLine = in.readLine()) != null)
            a.append(inputLine);
        in.close();

        out.println(a.toString());   

回答6:

I know this is an old question, but I'm sure other people will find it too.

If you don't mind an additional dependency, here's a very simple way

Jsoup.connect("http://example.com/").get().toString()

You'll need a Jsoup library, but you can quickly add it with maven/gradle and it also allows to manipulate the contents of the page and find specific nodes.