Java MD5校验

Java 生成MD5

MD5（Message Digest Algorithm），消息摘要算法，一般用于校验文件的完整性。Java内置已经实现了MD5，与SHA1算法,利用java.security.MessageDigest类就可以获取文件/字符串的MD5或SHA1

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5AndSHA1Helper {
    
    /**
     * 将字节数组转换为16进制字符串
     * @param resultArr
     * @return 16进制字符串
     */
    private static String byteArrToHex(byte[] byteArr) {
        // Initialize the character array, used to store each hexadecimal string
        char[] hexDigits = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
        // Initialize a char Array, used to form the result string
        char[] resultCharArr = new char[byteArr.length*2];
        // Traverse the byte array, converted into characters in a character array
        int index = 0;
        for (byte b : byteArr) {
            resultCharArr[index++] = hexDigits[b>>> 4 & 0xf];  
            resultCharArr[index++] = hexDigits[b & 0xf];
        }
        return new String(resultCharArr);
    }
    
    /**
     * 获取字符串的MD5
     * @param input
     * @return
     */
    public static String getStringMD5(String input){
        try {
            // get MD5 digest
            MessageDigest mDigest = MessageDigest.getInstance("MD5");
            // The input String to Byte Array
            byte[] inputArr = input.getBytes();
            // Updates the digest using the specified byte.
            mDigest.update(inputArr);
            // Completes the hash computation by performing final operations such as padding.
            // The digest is reset after this call is made.
            byte[] resultArr = mDigest.digest();
            // 
            return byteArrToHex(resultArr);
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
    
    /**
     * 获取文件的MD5，可以替换为SHA1
     * @param inputFile
     * @return
     * @throws IOException 
     */
    @SuppressWarnings("resource")
    public static String getFileMD5(String fileUrl) throws IOException{
        int bufferSize = 1024*1024;
        FileInputStream fileInputStream = null;
        DigestInputStream digestInputStream = null;
        try {
            // 可以替换为"SHA1"
            MessageDigest mDigest = MessageDigest.getInstance("MD5");
            fileInputStream = new FileInputStream(fileUrl);
            // Creates a digest input stream, using the specified input stream and message digest.
            digestInputStream = new DigestInputStream(fileInputStream, mDigest);
            byte[] buffer = new byte[bufferSize];
            while(digestInputStream.read(buffer)>0);
            mDigest = digestInputStream.getMessageDigest();
            byte[] resultArr = mDigest.digest();
            return byteArrToHex(resultArr);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }finally{
            fileInputStream.close();
            digestInputStream.close();
        }
        return null;
    }
    
    /**
     * 获取String的SHA1
     * @param input
     * @return
     */
    public static String getStringSHA1(String input){
        try {
            MessageDigest mDigest = MessageDigest.getInstance("SHA1");
            byte[] inputArr = input.getBytes();
            mDigest.update(inputArr);
            byte[] resultArr = mDigest.digest();
            return byteArrToHex(resultArr);
            
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
    
    

    
    public static void main(String[] args) {
//      String result = MD5AndSHA1Helper.getStringMD5("111");
//      String result = MD5AndSHA1Helper.getStringSHA1("1111");
        String path = "/Users/Dream_Kidd/Downloads/wanda19environment-x64/apache-tomcat-7.0.62-windows-x64.zip";
        String result;
        try {
            result = MD5AndSHA1Helper.getFileMD5(path);
            System.out.println(result);
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        
    }
}

建议，如果过G的文件，不建议使用Java自带的MD5

来源：https://www.cnblogs.com/dreamkidd/p/4511677.html