Работа с HTTP-протоколом

        HttpClient client = new HttpClient();
        PostMethod post = new PostMethod("http://vkontakte.ru/login.php");
        post.setParameter("app", "1862639");
        post.setParameter("layout", "popup");
        post.setParameter("type", "browser");
        post.setParameter("settings", "130");
        int code = client.executeMethod(post);
        String redirectLocation;
        Header locationHeader = post.getResponseHeader("location");
        if (locationHeader != null) {
            redirectLocation = locationHeader.getValue();
        } else {
            // The response is invalid and did not provide the new location for
            // the resource.  Report an error or possibly handle the response
            // like a 404 Not Found error.
        }

package com.db.gpf.gpfs.test;
import org.apache.commons.codec.binary.Hex;
import org.apache.log4j.Logger;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.*;
public class App {
    private static final Logger logger = Logger.getLogger(App.class);
    private static final Set<String> IGNORING_PARAMS;
    private static final Charset CHARSET = Charset.forName("UTF-8");
    static {
        ConfigurableToStringStyle.init("to-string-builder.properties");
        HashSet<String> set = new HashSet<String>();
        set.add("sid");
        IGNORING_PARAMS = Collections.unmodifiableSet(set);
    }
    private MessageDigest md5;
    private String userId;
    private String secret;
    public App(String userId, String secret) throws NoSuchAlgorithmException {
        md5 = MessageDigest.getInstance("MD5");
        this.userId = userId;
        this.secret = secret;
    }
    public String getChecksum(SortedMap<String, String> arguments) {
        StringBuilder buffer = new StringBuilder(512);
        buffer.append(userId);
        for (Map.Entry<String, String> entry : arguments.entrySet()) {
            String key = entry.getKey();
            String value = entry.getValue();
            if (IGNORING_PARAMS.contains(key)) {
                continue;
            }
            buffer.append(key).append('=').append(value);
        }
        buffer.append(secret);
        byte[] bytes = buffer.toString().getBytes(CHARSET);
        byte[] md5 = this.md5.digest(bytes);
        return Hex.encodeHexString(md5);
    }
    public static void main(String[] args) throws Exception {
        App app = new App("100172", "655df68ded");
        SortedMap<String, String> params = new TreeMap<String, String>();
        params.put("api_id", "1854119");
        params.put("fields", "photo,sex");
        params.put("format", "JSON");
        params.put("method", "getProfiles");
        params.put("sid", "25094e01b4fa6824a6d84a65b5b3a09998e17d18d91ba7d9059689da");
        params.put("uids", "100172");
        params.put("v", "3.0");
        String sig = app.getChecksum(params);
        logger.info(sig);
        params.put("sig", sig);
    }
}