Java Tips - How to fetch an HTML page

The J2ME code fetches the HTML page for a book and creates a BookInfo class instance. The code for the fetch() method of this class does all the work.

private static final String BASE_URL = "http://www.amazon.com";

private static final String QUERY_URL = BASE_URL +

  "/exec/obidos/search-handle-form/0";

private static final int MAX_REDIRECTS = 5;



public static boolean fetch(BookInfo info) throws IOException {



InputStream is = null;

OutputStream os = null;

HttpConnection conn = null;

int redirects = 0;



try {

  String isbn = info.getIsbn( );

  String query = "index=books&field-keywords=" + isbn + "\r\n";

  String requestMethod = HttpConnection.POST;

  String name = QUERY_URL;

  while (redirects < MAX_REDIRECTS) {

  conn = (HttpConnection)Connector.open(name,Connector.READ_WRITE);

  

  // Send the ISBN number to perform the query

  conn.setRequestMethod(requestMethod);

  

  if (requestMethod.equals(HttpConnection.POST)) {

    conn.setRequestProperty("Content-Type",

      "application/x-www-form-urlencoded");

    os = conn.openOutputStream( );

    os.write(query.getBytes( ));

    os.close( );

    os = null;

  }



  // Read the response from the server

  is = conn.openInputStream( );

  int code = conn.getResponseCode( );



  // If we get a redirect, try again at the new location

  if ((code >= HttpConnection.HTTP_MOVED_PERM && code <=

    HttpConnection.HTTP_SEE_OTHER) ||

    code == HttpConnection.HTTP_TEMP_REDIRECT) {



    // Get the URL of the new location (always absolute)

    name = conn.getHeaderField("Location");

    is.close( );

    conn.close( );

    is = null;

    conn = null;



    if (++redirects > MAX_REDIRECTS) {

      // Too many redirects - give up.

      break;

    }



    // Choose the appropriate request method

    requestMethod = HttpConnection.POST;



    if (code == HttpConnection.HTTP_MOVED_TEMP ||

      code == HttpConnection.HTTP_SEE_OTHER) {

      requestMethod = HttpConnection.GET;

    }



    continue;

  }





  String type = conn.getType( );



  if (code == HttpConnection.HTTP_OK && type.equals("text/html")){

    info.setFromInputStream(is);

    return true;

  }

}

} catch (Throwable t) {

  System.out.println(t);

} finally {

  // Tidy up code (not shown)

}



return false;

}
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