Util.java

package com.swjtu.util;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;

import java.io.*;
import java.net.URLEncoder;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Util {
    public static List<NameValuePair> map2list(Map<String, String> mapParams) {
        List<NameValuePair> listParams = new ArrayList<NameValuePair>();
        Iterator it = mapParams.entrySet().iterator();
        while(it.hasNext()) {
            Map.Entry entry = (Map.Entry)it.next();
            String key = String.valueOf(entry.getKey());
            String value = String.valueOf(entry.getValue());
            if (value != null) {
                listParams.add(new BasicNameValuePair(key, value));
            }
        }
        return listParams;
    }

    public static String getUrlWithQueryString(String url, Map<String, String> params) {
        if (params == null) {
            return url;
        }

        StringBuilder builder = new StringBuilder(url);
        if (url.contains("?")) {
            builder.append("&");
        } else {
            builder.append("?");
        }

        int index = 0;
        for (String key : params.keySet()) {
            String value = params.get(key);
            if (value == null) {
                continue;
            }
            if (index != 0) {
                builder.append("&");
            }
            index++;
            builder.append(key);
            builder.append("=");
            builder.append(encode(value));
        }
        return builder.toString();
    }

    private static String encode(String input) {
        if (input == null) {
            return "";
        }

        try {
            return URLEncoder.encode(input, "utf-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        return input;
    }

    private static final char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    public static String md5(String input) {
        if (input == null) {
            return null;
        }

        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            byte[] inputByteArray = input.getBytes("utf-8");
            messageDigest.update(inputByteArray);
            byte[] resultByteArray = messageDigest.digest();
            return byteArrayToHex(resultByteArray);
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            return null;
        }
    }

    public static String md5(File file) {
        try {
            if (!file.isFile()) {
                System.err.println("文件" + file.getAbsolutePath() + "不存在或者不是文件");
                return null;
            }

            FileInputStream in = new FileInputStream(file);
            String result = md5(in);
            in.close();

            return result;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String md5(InputStream in) {
        try {
            MessageDigest messagedigest = MessageDigest.getInstance("MD5");

            byte[] buffer = new byte[1024];
            int read;
            while ((read = in.read(buffer)) != -1) {
                messagedigest.update(buffer, 0, read);
            }
            in.close();
            return byteArrayToHex(messagedigest.digest());
        } catch (NoSuchAlgorithmException | IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    private static String byteArrayToHex(byte[] byteArray) {
        char[] resultCharArray = new char[byteArray.length * 2];
        int index = 0;
        for (byte b : byteArray) {
            resultCharArray[index++] = hexDigits[b >>> 4 & 0xf];
            resultCharArray[index++] = hexDigits[b & 0xf];
        }
        return new String(resultCharArray);
    }
}