How to use

openConnection

method

in

java.net.URL

public void postRequest(String urlStr, String jsonBodyStr) throws IOException {
  URL url = new URL(urlStr);
  HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
  httpURLConnection.setDoOutput(true);
  httpURLConnection.setRequestMethod("POST");
  httpURLConnection.setRequestProperty("Content-Type", "application/json");
  try (OutputStream outputStream = httpURLConnection.getOutputStream()) { 
   outputStream.write(jsonBodyStr.getBytes());
   outputStream.flush();
  }
  if (httpURLConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
    try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream()))) {
      String line;
      while ((line = bufferedReader.readLine()) != null) {
        // ... do something with line
      }
    }
  } else {
    // ... do something with unsuccessful response
  }
}

 HttpURLConnection httpConnection = (HttpURLConnection) new URL(url).openConnection();
httpConnection.setRequestMethod("POST");
// ...

 URLConnection connection = new URL(url + "?" + query).openConnection();
connection.setRequestProperty("Accept-Charset", charset);
InputStream response = connection.getInputStream();
// ...

 // First set the default cookie manager.
CookieHandler.setDefault(new CookieManager(null, CookiePolicy.ACCEPT_ALL));

// All the following subsequent URLConnections will use the same cookie manager.
URLConnection connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

connection = new URL(url).openConnection();
// ...

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

public class URLConnectionReader {
  public static void main(String[] args) throws Exception {
    URL yahoo = new URL("http://www.yahoo.com/");
    URLConnection yc = yahoo.openConnection();
    BufferedReader in = new BufferedReader(
                new InputStreamReader(
                yc.getInputStream()));
    String inputLine;

    while ((inputLine = in.readLine()) != null) 
      System.out.println(inputLine);
    in.close();
  }
}

  private static <T> T get(String url, Type type) throws IOException {
    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    con.setRequestMethod("GET");
    if (con.getResponseCode() == 200) {
      Reader reader = new InputStreamReader(con.getInputStream(), StandardCharsets.UTF_8);
      return GSON.fromJson(reader, type);
    }
    return null;
  }
}

  public static String readEc2MetadataUrl(MetaDataKey metaDataKey, URL url, int connectionTimeoutMs, int readTimeoutMs) throws IOException {
    HttpURLConnection uc = (HttpURLConnection) url.openConnection();
    uc.setConnectTimeout(connectionTimeoutMs);
    uc.setReadTimeout(readTimeoutMs);
    uc.setRequestProperty("User-Agent", "eureka-java-client");

    if (uc.getResponseCode() != HttpURLConnection.HTTP_OK) {  // need to read the error for clean connection close
      BufferedReader br = new BufferedReader(new InputStreamReader(uc.getErrorStream()));
      try {
        while (br.readLine() != null) {
          // do nothing but keep reading the line
        }
      } finally {
        br.close();
      }
    } else {
      return metaDataKey.read(uc.getInputStream());
    }

    return null;
  }
}

public static int getHttpCode() throws IOException {
 return ((HttpURLConnection) new URL("http://localhost:8080")
   .openConnection()).getResponseCode();
}

String sURL = "http://freegeoip.net/json/"; //just a string
 // Connect to the URL using java's native library
 URL url = new URL(sURL);
 HttpURLConnection request = (HttpURLConnection) url.openConnection();
 request.connect();
 // Convert to a JSON object to print data
 JsonParser jp = new JsonParser(); //from gson
 JsonElement root = jp.parse(new InputStreamReader((InputStream) request.getContent())); //Convert the input stream to a json element
 JsonObject rootobj = root.getAsJsonObject(); //May be an array, may be an object. 
 zipcode = rootobj.get("zip_code").getAsString(); //just grab the zipcode

 static ReturnCurrenciesResponse allCurrenciesStatic() throws IOException {
  HttpsURLConnection c =
    (HttpsURLConnection) new URL("https://api.idex.market/returnCurrencies").openConnection();
  c.setRequestMethod("POST");
  c.setRequestProperty("Accept-Encoding", "gzip");
  c.setRequestProperty("User-Agent", "irrelevant");
  try (InputStreamReader inputStreamReader =
    new InputStreamReader(new GZIPInputStream(c.getInputStream()))) {
   ObjectMapper objectMapper = new ObjectMapper();
   return objectMapper.readerFor(ReturnCurrenciesResponse.class).readValue(inputStreamReader);
  }
 }
}

 URL url = new URL("http://www.example.com/resource");
HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
httpCon.setDoOutput(true);
httpCon.setRequestMethod("PUT");
OutputStreamWriter out = new OutputStreamWriter(
  httpCon.getOutputStream());
out.write("Resource content");
out.close();
httpCon.getInputStream();

    URL url = classLoader.getResource(resourceName);
    if (url != null) {
      URLConnection connection = url.openConnection();
      if (connection != null) {
        connection.setUseCaches(false);
        is = connection.getInputStream();
String encoding = getDefaultEncoding();
if (encoding != null) {
  try (InputStreamReader bundleReader = new InputStreamReader(inputStream, encoding)) {
    return loadBundle(bundleReader);

  private static URLConnection fetchClass0(String host, int port,
                       String filename)
    throws IOException
  {
    URL url;
    try {
      url = new URL("http", host, port, filename);
    }
    catch (MalformedURLException e) {
      // should never reache here.
      throw new IOException("invalid URL?");
    }

    URLConnection con = url.openConnection();
    con.connect();
    return con;
  }
}

@Override
protected InputStream openObjectStream(URI object) throws IOException
{
 return object.toURL().openConnection().getInputStream();
}

 SSLSocketFactory sslsocketfactory = (SSLSocketFactory) SSLSocketFactory.getDefault();
URL url = new URL("https://gridserver:3049/cgi-bin/ls.py");
HttpsURLConnection conn = (HttpsURLConnection)url.openConnection();
conn.setSSLSocketFactory(sslsocketfactory);
InputStream inputstream = conn.getInputStream();
InputStreamReader inputstreamreader = new InputStreamReader(inputstream);
BufferedReader bufferedreader = new BufferedReader(inputstreamreader);

String string = null;
while ((string = bufferedreader.readLine()) != null) {
  System.out.println("Received " + string);
}

 HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
connection.setRequestMethod("HEAD");
int responseCode = connection.getResponseCode();
if (responseCode != 200) {
  // Not OK.
}

// < 100 is undetermined.
// 1nn is informal (shouldn't happen on a GET/HEAD)
// 2nn is success
// 3nn is redirect
// 4nn is client error
// 5nn is server error

 URLConnection connection = new URL(url).openConnection();
connection.setDoOutput(true); // Triggers POST.
connection.setRequestProperty("Accept-Charset", charset);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;charset=" + charset);

try (OutputStream output = connection.getOutputStream()) {
  output.write(query.getBytes(charset));
}

InputStream response = connection.getInputStream();
// ...

 HttpURLConnection httpUrlConnection = null;
URL url = new URL("http://example.com/server.cgi");
httpUrlConnection = (HttpURLConnection) url.openConnection();
httpUrlConnection.setUseCaches(false);
httpUrlConnection.setDoOutput(true);

httpUrlConnection.setRequestMethod("POST");
httpUrlConnection.setRequestProperty("Connection", "Keep-Alive");
httpUrlConnection.setRequestProperty("Cache-Control", "no-cache");
httpUrlConnection.setRequestProperty(
  "Content-Type", "multipart/form-data;boundary=" + this.boundary);

private int getHttpCode() throws IOException {
 return ((HttpURLConnection) new URL("http://localhost:8080")
   .openConnection()).getResponseCode();
}

 // Gather all cookies on the first request.
URLConnection connection = new URL(url).openConnection();
List<String> cookies = connection.getHeaderFields().get("Set-Cookie");
// ...

// Then use the same cookies on all subsequent requests.
connection = new URL(url).openConnection();
for (String cookie : cookies) {
  connection.addRequestProperty("Cookie", cookie.split(";", 2)[0]);
}
// ...