Connecting to the web

[karthikeyan g]

I tried the example given in java tech tips. But It always throws the exception "UnknownhostException" though I set the properties

System.setProperty("http.proxyHost","webcache");
System.setProperty("http.proxyPort","8080");

System.setProperty("https.proxyHost","webcache");
System.setProperty("https.proxyPort","8080");

I am using proxy setup for accessing the net.



import java.net.URL;
import java.net.MalformedURLException;
import java.net.URLConnection;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class WebPageReader {

private static URLConnection connection;

private static void connect( String urlString ) {
try {
URL url = new URL(urlString);
connection = url.openConnection();
} catch (MalformedURLException e){
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

private static void readContents() {
BufferedReader in = null;
try {
in = new BufferedReader(
new InputStreamReader(
connection.getInputStream()));

String inputLine;
while (
(inputLine = in.readLine()) != null) {
System.out.println(inputLine);
}
} catch (IOException e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
if (args.length != 1) {
System.err.println("usage: java WebPageReader "
+ "<url>");
System.exit(0);
}
connect(args[0]);
readContents();
}
}


Thanks

[hopefulcharlie]

I m not sure what you are trying to do, but following is a listing of a class that reads a csv file from the uk lottery site and simply shows it on the console.


import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

/**
* @version 1.0
* @author
*/
public class LoadFile2 {

public void loadFile(String inURL) throws IOException {

URL theURL = null;
try {
theURL = new URL(inURL);
} catch (MalformedURLException e) {
System.out.println("Bad URL: " + theURL);
}

URLConnection conn = null;
DataInputStream data = null;
String line;

try {
conn = theURL.openConnection();
conn.connect();

System.out.println("Connection opened...");

data =
new DataInputStream(
new BufferedInputStream(conn.getInputStream()));

System.out.println("Reading data...");
while ((line = data.readLine()) != null) {
System.out.println(line);
}

data.close();
} catch (IOException e) {
System.out.println("IO Error:" + e.getMessage());
}
}
/** Main. */
public static void main(String[] args) {
LoadFile2 loadFile2 = new LoadFile2();
try {
loadFile2.loadFile("http://www.national-lottery.co.uk/player/files/Lotto.csv");
} catch (IOException e) {
e.printStackTrace();
}

}
}

[Bchy_Fairy]

Well I had to make a connection to the server project for my class, I don't know if this could help but here it is my code:


WebClient.JAVA:

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

/**
* Receives a String from WebClientTester and converts it to URL type, connects
* to the server and checks whether is a correct or incorrect page.
*/
public class WebClient
{
//addr1 - a place holder for the address received by WebClientTester.java.
private String addr1;

//u - a place holder for the addr1 once it has been converted from String to URL type.
private URL u;

//huc - a place holder for the object that represents a connection to the URL.
private HttpURLConnection huc;

//finalResponse - the return value of the getResponse method.
private String finalResponse;

//Constructor WebClient, creates a new object of the WebClient Class.
public WebClient()
{
addr1=null;
}

/**
* Receives a String from WebClientTester converts it to URL type.
* To indicate the URL of the WebPage.
*
* @param addr Address received from WebClientTester but still String type.
* @throws MalformedURLException
*/
void setURL(String addr) throws MalformedURLException
{
addr1=addr;
u = new URL(addr1);
}

/**
* Gets the Server's Answer for the address given.
*
* @return finalResponse Returns the server's response of type String.
*/
String getResponse()
{
try
{
huc = (HttpURLConnection) u.openConnection();
finalResponse="HTTP/1.0 "+" "+huc.getResponseCode()+" "+huc.getResponseMessage();
}
catch (IOException e)
{
e.printStackTrace();
}

return finalResponse;
}


}

WebClientTester.java

import java.io.*;
import java.net.*;
import javax.swing.*;

/**
*Prints the Intro and the instructions for the user. Stores the user's input.
*Sends all the addresses to the callsWebClient method in order to eliminate code lines.
*/
public class WebClientTester
{

/**
* @param args
* @throws IOException
*/

public static void main(String[] args) throws IOException
{
WebClient address=new WebClient();

String addr1 ="http://www.google.com/";
String addr2 = "http://www.uprm.edu/";
String addr3 = "http://www.hotmail.com/";

//Graphical application that displays a frame window with a WELCOME.
JFrame window = new JFrame();
JLabel windowIcon = new JLabel(new ImageIcon("ComputerIcon.gif"));
JLabel windowText = new JLabel(" WELCOME TO THE PAGE-TESTER PROGRAM ");

JPanel panel= new JPanel();
panel.add(windowIcon);
panel.add(windowText);
window.setContentPane(panel);

window.pack();
window.show();


//Three correct addresses
System.out.println("* EXAMPLES OF CORRECT PAGES WITH CORRECT SERVERS *");
System.out.println();

System.out.println(addr1);
callsWebClient(addr1,address);

System.out.println(addr2);
callsWebClient(addr2,address);

System.out.println(addr3);
callsWebClient(addr3,address);

//Three incorrect addresses
System.out.println();
System.out.println("* EXAMPLES OF INCORRECT PAGES WITH CORRECT SERVERS *");
System.out.println();

System.out.println(addr1+"dfdcss");
callsWebClient(addr1+"dfdcss",address);

System.out.println(addr2+"dfdcss");
callsWebClient(addr2+"dfdcss",address);

System.out.println(addr3+"dfdcss");
callsWebClient(addr3+"dfdcss",address);

System.out.println();
System.out.println("----------------------------------------------------------------------------------------");
System.out.println(" ENTER A PAGE THAT YOU WOULD LIKE TO TEST WHETHER IT WORKS OR NOT");
System.out.println("----------------------------------------------------------------------------------------");
System.out.println();
System.out.println(" * PLEASE MAKE SURE TO FOLLOW THE FOLLOWING DESCRIPTION: http://ADDRESS_GOES_HERE *");
System.out.println(" ** NOTE: THE SERVER MUST BE CORRECT BUT THE PAGE INCORRECT OR I WILL THROW AN **");
System.out.println(" *** EXCEPTION ***");

//Reads a line of input and stores it in "input". Calls the callsWebClient method.
BufferedReader console=new BufferedReader(new InputStreamReader(System.in));
String input=console.readLine();
callsWebClient(input,address);


}

/**
* Prints the the response given from the server.
* Calls the getResponse and setURL methods from WebClient.java.
* It will be called from main method using a single line.
*
* @param addr String received from main that contains the address.
* @param address Needed to call the WebClient.java methods.
* @throws MalformedURLException
*/
public static void callsWebClient(String addr,WebClient address) throws MalformedURLException
{
address.setURL(addr);
System.out.println(address.getResponse());
System.out.println();
}
}