信息摘要工具类-MD5、CRC32、SHA1

　　信息摘要，通俗来说，就是信息的指纹。就像人类的指纹是不会重复的一样，使用信息摘要算法计算任何两个不同信息，得出的摘要（指纹）也是不一样的。

　　这通常用在校验文件是否被修改过，在Web项目中MD5也用在密码加密上。

　　下面的信息摘要工具类MsgDigest，可以计算文件的MD5、CRC32、SHA1摘要，字符串的MD5、SHA1摘要。

MsgDigest类：

package com.dong.framework.tool;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.zip.CRC32;

/**
* 信息摘要，可以获得CRC32、MD5、SHA-1值
* @version 1.0
* @author dongliyang
*/
public class MsgDigest {

/**
* 计算文件的32位循环冗余校验和CRC32
* @param filepath 文件名
* @return String
* @throws IOException IOException异常
*/
public static String crc32Digest(String filepath) {

try {

InputStream in = new BufferedInputStream(new FileInputStream(filepath));
CRC32 crc = new CRC32();

int c;
while((c = in.read()) != -1){
crc.update(c);
}
in.close();
return Long.toHexString(crc.getValue());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}

}

/**
* 计算文件的32位循环冗余校验和CRC32
* @param file 文件
* @return String
* @throws IOException IOException异常
*/
public static String crc32Digest(File file){

try {

InputStream in = new BufferedInputStream(new FileInputStream(file));
CRC32 crc = new CRC32();

int c;
while((c = in.read()) != -1){
crc.update(c);
}
in.close();
return Long.toHexString(crc.getValue());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}

}

/**
* 计算字符串的MD5值
* @param input 字符串
* @return String
*/
public static String md5Digest(String input){

byte[] data = input.getBytes();
try {
MessageDigest messageDigest = getMD5();
messageDigest.update(data);
return toHexString(messageDigest.digest());
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
}

}

/**
* 计算文件的MD5值
* @param filename 文件名
* @return String
*/
public static String md5FileDigest(String filepath){
String md5 = "";
File file = new File(filepath);
if(file.exists()){
try {
MessageDigest messageDigest = getMD5();
InputStream in = new BufferedInputStream(new FileInputStream(file));
byte[] cache = new byte[CACHE_SIZE];
int len;
while((len = in.read(cache)) != -1){
messageDigest.update(cache, 0, len);
}
in.close();
byte[] data = messageDigest.digest();
md5 = toHexString(data);
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}
}
return md5;
}

/**
* 计算文件的MD5值
* @param file 文件
* @return String
*/
public static String md5FileDigest(File file){

String md5 = "";
if(file.exists()){
try {
MessageDigest messageDigest = getMD5();
InputStream in = new BufferedInputStream(new FileInputStream(file));
byte[] cache = new byte[CACHE_SIZE];
int len;
while((len = in.read(cache)) != -1){
messageDigest.update(cache, 0, len);
}
in.close();
byte[] data = messageDigest.digest();
md5 = toHexString(data);
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}
}
return md5;
}

/**
* 计算字符串的SHA-1值
* @param input 字符串
* @return String
*/
public static String sha1Digest(String input){

byte[] data = input.getBytes();
try {
MessageDigest messageDigest = getSHA1();
messageDigest.update(data);
return toHexString(messageDigest.digest());
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
}
}

/**
* 计算文件的SHA-1值
* @param filepath 文件名
* @return String
*/
public static String sha1FileDigest(String filepath){

String sha1 = "";
File file = new File(filepath);
if(file.exists()){
try {
MessageDigest messageDigest = getSHA1();
InputStream in = new BufferedInputStream(new FileInputStream(file));
byte[] cache = new byte[CACHE_SIZE];
int len;
while((len = in.read(cache)) != -1){
messageDigest.update(cache, 0, len);
}
in.close();
byte[] data = messageDigest.digest();
sha1 = toHexString(data);
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}
}
return sha1;
}

/**
* 计算文件的SHA-1值
* @param file 文件
* @return String
*/
public static String sha1FileDigest(File file){

String sha1 = "";
if(file.exists()){
try {
MessageDigest messageDigest = getSHA1();
InputStream in = new BufferedInputStream(new FileInputStream(file));
byte[] cache = new byte[CACHE_SIZE];
int len;
while((len = in.read(cache)) != -1){
messageDigest.update(cache, 0, len);
}
in.close();
byte[] data = messageDigest.digest();
sha1 = toHexString(data);
} catch (NoSuchAlgorithmException e) {
System.out.println("MD5算法初始化失败!");
throw new RuntimeException(e.getMessage());
} catch (FileNotFoundException e) {
System.out.println("文件未找到异常!");
throw new RuntimeException(e.getMessage());
} catch (IOException e) {
System.out.println("IO异常!");
throw new RuntimeException(e.getMessage());
}
}
return sha1;

}
/**
* 字节数组转换为16进制字符串
* @param data 字节数组
* @return String
*/
private static String toHexString(byte[] data){
StringBuilder digestStr = new StringBuilder();
String stmp = "";
for(int i = 0;i < data.length; i++){
stmp = Integer.toHexString(data[i] & 0XFF);
if(stmp.length() == 1){
digestStr.append("0" + stmp);
}else {
digestStr.append(stmp);
}
}
return digestStr.toString();
}

/**
* 获取MD5实例
* @return MessageDigest
* @throws NoSuchAlgorithmException 异常
*/
private static MessageDigest getMD5() throws NoSuchAlgorithmException{
return MessageDigest.getInstance(ALGORIGTHM_MD5);
}

private static MessageDigest getSHA1() throws NoSuchAlgorithmException {
return MessageDigest.getInstance(ALGORIGTHM_SHA1);
}

/** MD5算法名称 */
private static final String ALGORIGTHM_MD5 = "MD5";
/** SHA-1算法名称 */
private static final String ALGORIGTHM_SHA1 ="SHA-1";
/** 字节数组缓存大小 */
private static final int CACHE_SIZE = 2048;
}