package org.sxkj.common.utils;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.net.URL;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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public class MD5Util {
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/**
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* 计算文件的“16位MD5”哈希值 (截取32位MD5的中间16位)
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*
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* @param file 要计算MD5的文件
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* @return 文件的“16位MD5”哈希字符串，如果发生错误或无法生成32位MD5则返回null
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*/
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public static String get16BitMD5Checksum(File file) {
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String fullMD5 = getFullMD5Checksum(file);
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if (fullMD5 != null && fullMD5.length() == 32) {
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// 截取第9到第24位 (索引8到23)
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return fullMD5.substring(8, 24);
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}
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return null;
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}
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/**
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* 计算文件的标准32位MD5哈希值
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*
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* @param file 要计算MD5的文件
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* @return 文件的32位MD5哈希字符串，如果发生错误则返回null
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*/
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public static String getFullMD5Checksum(File file) {
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if (file == null || !file.exists() || !file.isFile()) {
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System.err.println("Invalid file provided for MD5 calculation.");
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return null;
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}
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try (InputStream fis = new FileInputStream(file)) {
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MessageDigest md = MessageDigest.getInstance("MD5");
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byte[] buffer = new byte[8192]; // 缓冲区可以大一点，例如8KB
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int bytesRead;
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while ((bytesRead = fis.read(buffer)) != -1) {
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md.update(buffer, 0, bytesRead);
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}
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byte[] digest = md.digest();
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StringBuilder sb = new StringBuilder();
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for (byte b : digest) {
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sb.append(String.format("%02x", b));
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}
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return sb.toString();
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} catch (IOException | NoSuchAlgorithmException e) {
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e.printStackTrace();
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return null;
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}
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}
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public static String getMD5Checksum(File file) {
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try (InputStream fis = new FileInputStream(file)) {
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MessageDigest md = MessageDigest.getInstance("MD5");
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byte[] buffer = new byte[1024];
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int bytesRead;
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while ((bytesRead = fis.read(buffer)) != -1) {
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md.update(buffer, 0, bytesRead);
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}
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byte[] digest = md.digest();
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StringBuilder sb = new StringBuilder();
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for (byte b : digest) {
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sb.append(String.format("%02x", b));
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}
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return sb.toString();
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} catch (IOException | NoSuchAlgorithmException e) {
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e.printStackTrace();
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return null;
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}
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}
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/**
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* 【核心方法】从任意输入流计算 MD5 校验和。
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* @param is 输入流
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* @return 32位的十六进制 MD5 字符串
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* @throws NoSuchAlgorithmException 如果 MD5 算法不可用
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* @throws IOException 如果流读取失败
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*/
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private static String calculateMD5(InputStream is) throws NoSuchAlgorithmException, IOException {
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MessageDigest md = MessageDigest.getInstance("MD5");
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byte[] buffer = new byte[8192]; // 8KB 缓冲区
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int bytesRead;
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while ((bytesRead = is.read(buffer)) != -1) {
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md.update(buffer, 0, bytesRead);
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}
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byte[] digest = md.digest();
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StringBuilder sb = new StringBuilder();
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for (byte b : digest) {
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sb.append(String.format("%02x", b));
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}
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return sb.toString();
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}
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/**
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* 【新增方法】从网络 URL 计算文件的 MD5 校验和。
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* @param urlString 文件的网络地址
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* @return 32位的十六进制 MD5 字符串，如果出错则返回 null
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*/
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public static String getMD5ChecksumFromUrl(String urlString) {
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try {
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URL url = new URL(urlString);
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// try-with-resources 确保网络流被关闭
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try (InputStream is = url.openStream()) {
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return calculateMD5(is);
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}
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} catch (IOException | NoSuchAlgorithmException e) {
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// MalformedURLException 是 IOException 的子类，所以会被捕获
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e.printStackTrace();
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return null;
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}
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}
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public static String getMD5Checksum(String input) {
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try {
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MessageDigest md = MessageDigest.getInstance("MD5");
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byte[] bytes = input.getBytes();
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md.update(bytes);
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byte[] digest = md.digest();
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StringBuilder sb = new StringBuilder();
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for (byte b : digest) {
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sb.append(String.format("%02x", b));
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}
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return sb.toString();
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} catch (NoSuchAlgorithmException e) {
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e.printStackTrace();
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return null;
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}
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}
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}
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