1/8/2008

Make HTTP POST Or GET Request From Java

Filed under: — Aviran Mordo @ 5:36 am

In this day of age where many applications need to communicate with web servers you need to make a simple HTTP call to the server. Usually There are two types of calls you’ll need to make an HTTP GET or HTTP POST. So instead of blabbing words, here is a code sample of how you do it.

Code example (sorry for the lack of formatting):


package HTTPUtil;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;
import java.net.URLConnection;

public class HTTPRequestPoster
{
/**
* Sends an HTTP GET request to a url
*
* @param endpoint - The URL of the server. (Example: " http://www.yahoo.com/search")
* @param requestParameters - all the request parameters (Example: "param1=val1&param2=val2"). Note: This method will add the question mark (?) to the request - DO NOT add it yourself
* @return - The response from the end point
*/
public static String sendGetRequest(String endpoint, String requestParameters)
{
String result = null;
if (endpoint.startsWith("http://"))
{
// Send a GET request to the servlet
try
{
// Construct data
StringBuffer data = new StringBuffer();

// Send data
String urlStr = endpoint;
if (requestParameters != null && requestParameters.length () > 0)
{
urlStr += "?" + requestParameters;
}
URL url = new URL(urlStr);
URLConnection conn = url.openConnection ();

// Get the response
BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuffer sb = new StringBuffer();
String line;
while ((line = rd.readLine()) != null)
{
sb.append(line);
}
rd.close();
result = sb.toString();
} catch (Exception e)
{
e.printStackTrace();
}
}
return result;
}

/**
* Reads data from the data reader and posts it to a server via POST request.
* data - The data you want to send
* endpoint - The server's address
* output - writes the server's response to output
* @throws Exception
*/
public static void postData(Reader data, URL endpoint, Writer output) throws Exception
{
HttpURLConnection urlc = null;
try
{
urlc = (HttpURLConnection) endpoint.openConnection();
try
{
urlc.setRequestMethod("POST");
} catch (ProtocolException e)
{
throw new Exception("Shouldn't happen: HttpURLConnection doesn't support POST??", e);
}
urlc.setDoOutput(true);
urlc.setDoInput(true);
urlc.setUseCaches(false);
urlc.setAllowUserInteraction(false);
urlc.setRequestProperty("Content-type", "text/xml; charset=" + "UTF-8");

OutputStream out = urlc.getOutputStream();

try
{
Writer writer = new OutputStreamWriter(out, "UTF-8");
pipe(data, writer);
writer.close();
} catch (IOException e)
{
throw new Exception("IOException while posting data", e);
} finally
{
if (out != null)
out.close();
}

InputStream in = urlc.getInputStream();
try
{
Reader reader = new InputStreamReader(in);
pipe(reader, output);
reader.close();
} catch (IOException e)
{
throw new Exception("IOException while reading response", e);
} finally
{
if (in != null)
in.close();
}

} catch (IOException e)
{
throw new Exception("Connection error (is server running at " + endpoint + " ?): " + e);
} finally
{
if (urlc != null)
urlc.disconnect();
}
}

/**
* Pipes everything from the reader to the writer via a buffer
*/
private static void pipe(Reader reader, Writer writer) throws IOException
{
char[] buf = new char[1024];
int read = 0;
while ((read = reader.read(buf)) >= 0)
{
writer.write(buf, 0, read);
}
writer.flush();
}

}

 

7 Responses to “Make HTTP POST Or GET Request From Java”

  1. Frank Says:

    Thanks, this has been useful.

    -Frank

  2. xavier Says:

    Hello!….I whant make 1 page of internet and i don’t know how …Can you help me?Plz contact me !!!

  3. Brian Says:

    How do I properly create the reader object for the postData function?

  4. Brian Says:

    Update: this works
    new StringReader(”type=1&keyword=abc”)

  5. elmih Says:

    thanks, this was really helpful!

  6. Dave Says:

    The “postData()” method does not work. I can’t find a sample on line that does. Every time I get the same thing:
    Server returned HTTP response code: 405 for URL

    If not that error, other samples give this:
    Unexpected end of file from server

    Why can’t people post working samples? IF I’m suppose to set headers to do a post expected by the server I hit, HOW do I find our what headers need to be set?

  7. Brian Says:

    URL formAction = new URL(”http://targetsite.com/search.php”);
    FileWriter fw = new FileWriter (”results.html”);
    postData(new StringReader(”type=1&keyword=abc”), formAction, fw);
    fw.close();

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