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