Get html file Java

Question

Duplicate:

How do you Programmatically Download a Webpage in Java?

How to fetch html in Java

I'm developping an application that consists on: the user inputs an URL of some website, and then the application have to analyze that URL.

How can I have access to the HTML file, using Java? Does I need to use HttpRequest? How does that works?

Thks.

Answer 1

You could just use a URLConnection. See this Java Tutorial from Sun

Answer 2

You can use java.net.URL and then open an input stream to read the HTML from the server. See the example here.

Answer 3

URLConnection is fine for simple cases. When there are things like redirections involved, you are better off using Apache's HTTPClient

Answer 4

This code downloads data from a URL, treating it as binary content:

public class Download {

  private static void download(URL input, File output)
      throws IOException {
    InputStream in = input.openStream();
    try {
      OutputStream out = new FileOutputStream(output);
      try {
        copy(in, out);
      } finally {
        out.close();
      }
    } finally {
      in.close();
    }
  }

  private static void copy(InputStream in, OutputStream out)
      throws IOException {
    byte[] buffer = new byte[1024];
    while (true) {
      int readCount = in.read(buffer);
      if (readCount == -1) {
        break;
      }
      out.write(buffer, 0, readCount);
    }
  }

  public static void main(String[] args) {
    try {
      URL url = new URL("http://stackoverflow.com");
      File file = new File("data");
      download(url, file);
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

}

The downside of this approach is that it ignores any meta-data, like the Content-Type, which you would get from using HttpURLConnection (or a more sophisticated API, like the Apache one).

In order to parse the HTML data, you'll either need a specialized HTML parser that can handle poorly formed markup or tidy it first before parsing using a XML parser.

Answer 5

Funnily enough I wrote utility method that does just that the other week

/**
 * Retrieves the file specified by <code>fileUrl</code> and writes it to 
 * <code>out</code>.
 * <p>
 * Does not close <code>out</code>, but does flush.
 * @param fileUrl The URL of the file.
 * @param out An output stream to capture the contents of the file
 * @param batchWriteSize The number of bytes to write to <code>out</code>
 *                       at once (larger files than this will be written
 *                       in several batches)
 * @throws IOException If call to web server fails
 * @throws FileNotFoundException If the call to the web server does not
 *                               return status code 200. 
 */
public static void getFileStream(String fileURL, OutputStream out, int batchWriteSize)
       throws IOException{
 GetMethod get = new GetMethod(fileURL);
 HttpClient client = new HttpClient();
 HttpClientParams params = client.getParams();
 params.setSoTimeout(2000);
 client.setParams(params);
 try {
  client.executeMethod(get);
 } catch(ConnectException e){
  // Add some context to the exception and rethrow
  throw new IOException("ConnectionException trying to GET " + 
    fileURL,e);
 }

 if(get.getStatusCode()!=200){
  throw new FileNotFoundException(
    "Server returned " + get.getStatusCode());
 }

 // Get the input stream
 BufferedInputStream bis = 
  new BufferedInputStream(get.getResponseBodyAsStream());

 // Read the file and stream it out
 byte[] b = new byte[batchWriteSize];
 int bytesRead = bis.read(b,0,batchWriteSize);
 long bytesTotal = 0;
 while(bytesRead!=-1) {
  bytesTotal += bytesRead;
  out.write(b, 0, bytesRead);
  bytesRead = bis.read(b,0,batchWriteSize);;
 } 
 bis.close(); // Release the input stream.
 out.flush();   
}

Uses Apache Commons library i.e.

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.params.HttpClientParams;