How to extract data at the server end?

I have used the following code on my c开发者_如何转开发lient side (Android emulator).

HttpClient client=new DefaultHttpClient();
HttpPost httpPost=new HttpPost("http://117.192.xxx.xxx:8080/System_Alpha/");
List pairs=new  ArrayList();
String strUsername=username.getText().toString();
String strPassword=password.getText().toString();
pairs.add(new BasicNameValuePair("username", strUsername));
pairs.add(new BasicNameValuePair("password", strPassword));
httpPost.setEntity(new UrlEncodedFormEntity(pairs));
HttpResponse response= client.execute(httpPost);

My question is, at the server end, how can I extract these values? That is, the username and password?

That depends on what you have on the server side.

Say: if you have a java servlet, you just retrieve the necessary data in your doGet (resp. doPost) method:

final String userName = (String) request.getParameter("userName");
final String password = (String) request.getParameter("password");

Update 1
Here is an example of a simple servlet that authenticates a user with the two parameters above, and sends back an xml response:

public class LoginServlet extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
        throws ServletException, IOException
    {
        response.setContentType("text/xml");
        final ServletOutputStream out = response.getOutputStream();
        try
        {
            final String userName = (String) request.getParameter("userName");
            final String password = (String) request.getParameter("password");
            final boolean authenticated = login(userName, password);
            if (authenticated)
                out.println("<login><status>SUCCESS</status></login>");
            else
                out.println("<login><status>FAIL</status></login>");
        }
        catch (Exception e)
        {
            out.println("<login><status>ERROR</status></login>");
        }
        out.flush();
        out.close();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) 
        throws ServletException, IOException
    {
        this.doGet(request, response);
    }

    private boolean login(final String userName, final String password)
    {
        // TODO: authenticate the user and return the result: true/false
    }
}

In your web.xml you declare your servlet by writing:

<servlet>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>[yourpackagename].LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet/*</url-pattern>
</servlet-mapping>

where [yourpackagename] is the package where your LoginServlet is declared.

This way, if all these are in a web application named Try, and you deploy it, you can access your login servlet over http at http://localhost:8080/Try/LoginServlet/.

Update 2
To retrieve the data from the HttpResponse, you need:

HttpEntity entity = response.getEntity();
final InputStream inputStream = entity.getContent();

You handle this InputStream depending on what kind of data it contains.

If you need the String value of the response entity:

HttpEntity entity = response.getEntity();
final String responseText = EntityUtils.toString(entity);