Summary: Sample Java code that reads over a URLConnection reads only certain URLs, not others.
Details: I have this sample Java code that I am using to read over a URLConnection. When the URL is "http://www.example.com", the code reads the page content without any issues. However, if the URL is "http://www.cnn.com", the page content is not read
public class StackOverflow {
public static void main(String[] args) throws Exception {
BufferedReader inputStream = null;
try {
String urlStr = "http://www.cnn.com"; // Does not work
// urlStr = "http://www.example.com"; // **Works if this line is uncommented**
URL url = new URL(urlStr);
inputStream = new BufferedReader(new InputStreamReader(url.openStream()));
String textLine = null;
while((textLine = inputStream.readLine()) != null) {
System.out.println(textLine);
}
}
catch (Exception e) {
e.printStackTrace();
}
finally {
if(inputStream != null) inputStream.close();
}
}
}
CNN redirects from http to https but your call doesn't follow redirects. You are getting a 307 with an empty body so the readline results in a null and your loop is skipped. Try with https for CNN.
So i have this simple method to download and replace a file:
public void checkForUpdates() {
try {
URL website = new URL(downloadFrom);
ReadableByteChannel rbc = Channels.newChannel(website.openStream());
FileOutputStream fos = new FileOutputStream(downloadTo);
fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
fos.close();
rbc.close();
} catch (IOException e) {
System.out.println("No files found");
}
}
How can i check if there is a concrete file with a certain name located in the destination (downloadFrom) ? Right now if there are no files it downloads the html page.
You can get content type from header
URL url = new URL(urlname);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("HEAD");
connection.connect();
String contentType = connection.getContentType();
then check it's HTML/text or files.
I suggest to check the HTTP code for code 200. Something along these lines:
public class DownloadCheck {
public static void main(String[] args) throws IOException {
System.out.println(hasDownload("http://www.google.com"));
System.out.println(hasDownload("http://www.google.com/bananas"));
}
private static boolean hasDownload(String downloadFrom) throws IOException {
URL website = new URL(downloadFrom);
HttpURLConnection connection = null;
try {
connection = (HttpURLConnection) website.openConnection();
return connection.getResponseCode() == 200; // You could check other codes though
}
catch (Exception e) {
Logger.getLogger(OffersUrlChecker.class.getName()).log(Level.SEVERE,
String.format("Could not read from %s", downloadFrom), e);
return false;
}
finally {
if (connection != null) {
connection.disconnect(); // Make sure you close the sockets
}
}
}
}
If you run this code, you will get:
true
false
as the output.
You could consider to consider other code than code 200 as OK. See more information on HTTP codes here.
I am trying to get recharge plan information of service provider into my java program, the website contains dynamic data, and when i am fetching the URL using URLConnection i am only getting the static content,I want to automate the recharge plans of different website into my program.
package com.fs.store.test;
import java.net.*;
import java.io.*;
public class MyURLConnection
{
private static final String baseTataUrl = "https://www.tatadocomo/pre-paypacks";`enter code here`
public MyURLConnection()
{
}
public void getMeData()
{
URLConnection urlConnection = null;
BufferedReader in = null;
try
{
URL url = new URL(baseTataUrl);
urlConnection = url.openConnection();
HttpURLConnection connection = null;
connection = (HttpURLConnection) urlConnection;
in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()/*,"UTF-8"*/));
String currentLine = null;
StringBuilder line = new StringBuilder();
while((currentLine = in.readLine()) != null)
{
System.out.println(currentLine);
line = line.append(currentLine.trim());
}
}catch(IOException e)
{
e.printStackTrace();
}
finally{
try{
in.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
public static void main (String args[])
{
MyURLConnection test = new MyURLConnection();
System.out.println("About to call getMeData()");
test.getMeData();
}
}
You must use one of HtmlEditorKits
with Javascript enabled in your browser
and then get content.
See examples:
oreilly
Inspect the traffjc. Firefox has a TamperData plugin for instance. Then you may communicate more directly.
Use apache's HttpClient to facilitate the communication, instead of plain URL.
Maybe use some JSON library if JSON data are coming back.
More details, but you might now skip some loading.
So I'm trying to download the text of an aspx webpage (Roblox) with java. My code looks like this:
URL url;
InputStream is = null;
DataInputStream dis;
String line = "";
try {
System.out.println("connecting");
url = new URL("http://www.roblox.com");
is = url.openStream(); // throws an IOException
dis = new DataInputStream(new BufferedInputStream(is));
while ((line = dis.readLine()) != null) {
System.out.println(line);
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
is.close();
} catch (IOException ioe) {}
}
And it works for www.roblox.com. However, when I try to navigate to a different page - http://www.roblox.com/My/Money.aspx#/#TradeCurrency_tab
- it doesn't work, and just loads the www.roblox.com screen.
Could anyone help clarify this? Any help would be appreciated.
You are getting different content in java than you see in the browser because the server adds the following header to the response:
Location=https://www.roblox.com/Login/Default.aspx?ReturnUrl=%2fMy%2fMoney.aspx
You should get headers' values from URLConnection and redirect manually if the 'Location' header is present. As far as I know even if you used HttpConnection you won't be redirect automatically to 'https'
EDITED:
You could do it with smth like this (I removed other code, like exception handling just to focus on redirection, so don't take it as proper 'coding' example):
public static void main(String[] args) throws Exception {
printPage("http://www.roblox.com/My/Money.aspx#/#TradeCurrency_tab");
}
public static void printPage(String address) throws Exception {
String line = null;
System.out.println("connecting to:" + address);
URL url = new URL(address);
URLConnection conn = url.openConnection();
String redirectAdress = conn.getHeaderField("Location");
if (redirectAdress != null) {
printPage(redirectAdress);
} else {
InputStream is = url.openStream();
DataInputStream dis = new DataInputStream(new BufferedInputStream(is));
while ((line = dis.readLine()) != null) {
System.out.println(line);
}
}
}
Judging by the URL and the use of # I suspect this page is using javascript to dynamically create pages.
You can use something like http://seleniumhq.org/ to emulate a web-browser (including cookies) and this is a far more reliable approach for any kind of dynamic web content.
// The Firefox driver supports javascript
WebDriver driver = new FirefoxDriver();
// Go to the roblox page
driver.get("http://www.roblox.com");
System.out.println(driver.getPageSource());
Of course, there are many better ways to access elements of a page via Selenium's WebDriver API: http://selenium.googlecode.com/svn/trunk/docs/api/java/org/openqa/selenium/WebDriver.html
Download the JAR and all the deps in one file: http://code.google.com/p/selenium/downloads/detail?name=selenium-server-standalone-2.27.0.jar
And note, you can navigate to other pages via code: http://seleniumhq.org/docs/03_webdriver.html -
WebElement link = driver.findElement(By.linkText("Click Here Or Whatever"));
link.click();
then
System.out.println(driver.getPageSource());
will get the page text on the next page.
I would like to be able to fetch a web page's html and save it to a String, so I can do some processing on it. Also, how could I handle various types of compression.
How would I go about doing that using Java?
I'd use a decent HTML parser like Jsoup. It's then as easy as:
String html = Jsoup.connect("http://stackoverflow.com").get().html();
It handles GZIP and chunked responses and character encoding fully transparently. It offers more advantages as well, like HTML traversing and manipulation by CSS selectors like as jQuery can do. You only have to grab it as Document, not as a String.
Document document = Jsoup.connect("http://google.com").get();
You really don't want to run basic String methods or even regex on HTML to process it.
See also:
What are the pros and cons of leading HTML parsers in Java?
Here's some tested code using Java's URL class. I'd recommend do a better job than I do here of handling the exceptions or passing them up the call stack, though.
public static void main(String[] args) {
URL url;
InputStream is = null;
BufferedReader br;
String line;
try {
url = new URL("http://stackoverflow.com/");
is = url.openStream(); // throws an IOException
br = new BufferedReader(new InputStreamReader(is));
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (MalformedURLException mue) {
mue.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
try {
if (is != null) is.close();
} catch (IOException ioe) {
// nothing to see here
}
}
}
Bill's answer is very good, but you may want to do some things with the request like compression or user-agents. The following code shows how you can various types of compression to your requests.
URL url = new URL(urlStr);
HttpURLConnection conn = (HttpURLConnection) url.openConnection(); // Cast shouldn't fail
HttpURLConnection.setFollowRedirects(true);
// allow both GZip and Deflate (ZLib) encodings
conn.setRequestProperty("Accept-Encoding", "gzip, deflate");
String encoding = conn.getContentEncoding();
InputStream inStr = null;
// create the appropriate stream wrapper based on
// the encoding type
if (encoding != null && encoding.equalsIgnoreCase("gzip")) {
inStr = new GZIPInputStream(conn.getInputStream());
} else if (encoding != null && encoding.equalsIgnoreCase("deflate")) {
inStr = new InflaterInputStream(conn.getInputStream(),
new Inflater(true));
} else {
inStr = conn.getInputStream();
}
To also set the user-agent add the following code:
conn.setRequestProperty ( "User-agent", "my agent name");
Well, you could go with the built-in libraries such as URL and URLConnection, but they don't give very much control.
Personally I'd go with the Apache HTTPClient library.
Edit: HTTPClient has been set to end of life by Apache. The replacement is: HTTP Components
All the above mentioned approaches do not download the web page text as it looks in the browser. these days a lot of data is loaded into browsers through scripts in html pages. none of above mentioned techniques supports scripts, they just downloads the html text only. HTMLUNIT supports the javascripts. so if you are looking to download the web page text as it looks in the browser then you should use HTMLUNIT.
You'd most likely need to extract code from a secure web page (https protocol). In the following example, the html file is being saved into c:\temp\filename.html Enjoy!
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;
/**
* <b>Get the Html source from the secure url </b>
*/
public class HttpsClientUtil {
public static void main(String[] args) throws Exception {
String httpsURL = "https://stackoverflow.com";
String FILENAME = "c:\\temp\\filename.html";
BufferedWriter bw = new BufferedWriter(new FileWriter(FILENAME));
URL myurl = new URL(httpsURL);
HttpsURLConnection con = (HttpsURLConnection) myurl.openConnection();
con.setRequestProperty ( "User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0" );
InputStream ins = con.getInputStream();
InputStreamReader isr = new InputStreamReader(ins, "Windows-1252");
BufferedReader in = new BufferedReader(isr);
String inputLine;
// Write each line into the file
while ((inputLine = in.readLine()) != null) {
System.out.println(inputLine);
bw.write(inputLine);
}
in.close();
bw.close();
}
}
To do so using NIO.2 powerful Files.copy(InputStream in, Path target):
URL url = new URL( "http://download.me/" );
Files.copy( url.openStream(), Paths.get("downloaded.html" ) );
On a Unix/Linux box you could just run 'wget' but this is not really an option if you're writing a cross-platform client. Of course this assumes that you don't really want to do much with the data you download between the point of downloading it and it hitting the disk.
Get help from this class it get code and filter some information.
public class MainActivity extends AppCompatActivity {
EditText url;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate( savedInstanceState );
setContentView( R.layout.activity_main );
url = ((EditText)findViewById( R.id.editText));
DownloadCode obj = new DownloadCode();
try {
String des=" ";
String tag1= "<div class=\"description\">";
String l = obj.execute( "http://www.nu.edu.pk/Campus/Chiniot-Faisalabad/Faculty" ).get();
url.setText( l );
url.setText( " " );
String[] t1 = l.split(tag1);
String[] t2 = t1[0].split( "</div>" );
url.setText( t2[0] );
}
catch (Exception e)
{
Toast.makeText( this,e.toString(),Toast.LENGTH_SHORT ).show();
}
}
// input, extrafunctionrunparallel, output
class DownloadCode extends AsyncTask<String,Void,String>
{
#Override
protected String doInBackground(String... WebAddress) // string of webAddress separate by ','
{
String htmlcontent = " ";
try {
URL url = new URL( WebAddress[0] );
HttpURLConnection c = (HttpURLConnection) url.openConnection();
c.connect();
InputStream input = c.getInputStream();
int data;
InputStreamReader reader = new InputStreamReader( input );
data = reader.read();
while (data != -1)
{
char content = (char) data;
htmlcontent+=content;
data = reader.read();
}
}
catch (Exception e)
{
Log.i("Status : ",e.toString());
}
return htmlcontent;
}
}
}
Jetty has an HTTP client which can be use to download a web page.
package com.zetcode;
import org.eclipse.jetty.client.HttpClient;
import org.eclipse.jetty.client.api.ContentResponse;
public class ReadWebPageEx5 {
public static void main(String[] args) throws Exception {
HttpClient client = null;
try {
client = new HttpClient();
client.start();
String url = "http://example.com";
ContentResponse res = client.GET(url);
System.out.println(res.getContentAsString());
} finally {
if (client != null) {
client.stop();
}
}
}
}
The example prints the contents of a simple web page.
In a Reading a web page in Java tutorial I have written six examples of dowloading a web page programmaticaly in Java using URL, JSoup, HtmlCleaner, Apache HttpClient, Jetty HttpClient, and HtmlUnit.
I used the actual answer to this post (url) and writing the output into a
file.
package test;
import java.net.*;
import java.io.*;
public class PDFTest {
public static void main(String[] args) throws Exception {
try {
URL oracle = new URL("http://www.fetagracollege.org");
BufferedReader in = new BufferedReader(new InputStreamReader(oracle.openStream()));
String fileName = "D:\\a_01\\output.txt";
PrintWriter writer = new PrintWriter(fileName, "UTF-8");
OutputStream outputStream = new FileOutputStream(fileName);
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println(inputLine);
writer.println(inputLine);
}
in.close();
} catch(Exception e) {
}
}
}