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