你是否在寻找用Java实现MD5或SHA加密算法的案例

本文目录导读：

1. 使用Java内置的MessageDigest类
2. 使用Apache Commons Codec库
3. 带盐值的SHA加密
4. 完整的工具类
5. 注意事项

我来为你提供Java中实现MD5和SHA加密算法的完整案例。

使用Java内置的MessageDigest类

MD5加密示例

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class MD5Example {
    public static String md5Encrypt(String input) {
        try {
            // 创建MD5摘要对象
            MessageDigest md = MessageDigest.getInstance("MD5");
            // 计算MD5值
            byte[] digest = md.digest(input.getBytes());
            // 将字节数组转换为16进制字符串
            StringBuilder hexString = new StringBuilder();
            for (byte b : digest) {
                String hex = Integer.toHexString(0xff & b);
                if (hex.length() == 1) {
                    hexString.append('0');
                }
                hexString.append(hex);
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("MD5算法不存在", e);
        }
    }
    public static void main(String[] args) {
        String text = "Hello World";
        System.out.println("原始文本: " + text);
        System.out.println("MD5加密: " + md5Encrypt(text));
        // 验证
        String hash1 = md5Encrypt("Hello World");
        String hash2 = md5Encrypt("Hello World");
        System.out.println("两次加密结果相同: " + hash1.equals(hash2));
    }
}

SHA-256加密示例

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class SHAExample {
    public static String sha256Encrypt(String input) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            byte[] digest = md.digest(input.getBytes());
            StringBuilder sb = new StringBuilder();
            for (byte b : digest) {
                sb.append(String.format("%02x", b & 0xff));
            }
            return sb.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("SHA-256算法不存在", e);
        }
    }
    public static String sha512Encrypt(String input) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-512");
            byte[] digest = md.digest(input.getBytes());
            StringBuilder sb = new StringBuilder();
            for (byte b : digest) {
                sb.append(String.format("%02x", b & 0xff));
            }
            return sb.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("SHA-512算法不存在", e);
        }
    }
    public static void main(String[] args) {
        String text = "Hello World";
        System.out.println("原始文本: " + text);
        System.out.println("SHA-256: " + sha256Encrypt(text));
        System.out.println("SHA-512: " + sha512Encrypt(text));
    }
}

使用Apache Commons Codec库

首先添加Maven依赖：

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.15</version>
</dependency>

import org.apache.commons.codec.digest.DigestUtils;
public class CommonsCodecExample {
    public static void main(String[] args) {
        String text = "Hello World";
        // MD5
        String md5Hex = DigestUtils.md5Hex(text);
        System.out.println("MD5: " + md5Hex);
        // SHA-256
        String sha256Hex = DigestUtils.sha256Hex(text);
        System.out.println("SHA-256: " + sha256Hex);
        // SHA-512
        String sha512Hex = DigestUtils.sha512Hex(text);
        System.out.println("SHA-512: " + sha512Hex);
    }
}

带盐值的SHA加密

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;
public class SaltedHashExample {
    // 生成随机盐值
    public static byte[] generateSalt() {
        SecureRandom random = new SecureRandom();
        byte[] salt = new byte[16];
        random.nextBytes(salt);
        return salt;
    }
    // 带盐值的SHA-256加密
    public static String sha256WithSalt(String password, byte[] salt) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(salt);  // 添加盐值
            byte[] hashedPassword = md.digest(password.getBytes());
            // 将盐值和哈希值合并存储
            byte[] combined = new byte[salt.length + hashedPassword.length];
            System.arraycopy(salt, 0, combined, 0, salt.length);
            System.arraycopy(hashedPassword, 0, combined, salt.length, hashedPassword.length);
            return Base64.getEncoder().encodeToString(combined);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("SHA-256算法不存在", e);
        }
    }
    // 验证密码
    public static boolean verifyPassword(String password, String storedHash) {
        try {
            // 解码存储的哈希值
            byte[] combined = Base64.getDecoder().decode(storedHash);
            // 提取盐值（前16字节）
            byte[] salt = new byte[16];
            System.arraycopy(combined, 0, salt, 0, 16);
            // 计算密码的哈希值
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(salt);
            byte[] hashedPassword = md.digest(password.getBytes());
            // 比较哈希值
            for (int i = 0; i < hashedPassword.length; i++) {
                if (hashedPassword[i] != combined[i + 16]) {
                    return false;
                }
            }
            return true;
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("SHA-256算法不存在", e);
        }
    }
    public static void main(String[] args) {
        String password = "myPassword123";
        byte[] salt = generateSalt();
        String hashedPassword = sha256WithSalt(password, salt);
        System.out.println("密码哈希值: " + hashedPassword);
        // 验证密码
        boolean isMatch = verifyPassword("myPassword123", hashedPassword);
        System.out.println("密码验证结果: " + isMatch);
        boolean isNotMatch = verifyPassword("wrongPassword", hashedPassword);
        System.out.println("错误密码验证结果: " + isNotMatch);
    }
}

完整的工具类

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class HashUtils {
    // 支持的算法类型
    public enum Algorithm {
        MD5("MD5"),
        SHA1("SHA-1"),
        SHA256("SHA-256"),
        SHA512("SHA-512");
        private final String algorithm;
        Algorithm(String algorithm) {
            this.algorithm = algorithm;
        }
        public String getAlgorithm() {
            return algorithm;
        }
    }
    // 通用加密方法
    public static String hash(String input, Algorithm algorithm) {
        try {
            MessageDigest md = MessageDigest.getInstance(algorithm.getAlgorithm());
            byte[] digest = md.digest(input.getBytes());
            StringBuilder sb = new StringBuilder();
            for (byte b : digest) {
                sb.append(String.format("%02x", b & 0xff));
            }
            return sb.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(algorithm.getAlgorithm() + "算法不存在", e);
        }
    }
    // 便捷方法
    public static String md5(String input) {
        return hash(input, Algorithm.MD5);
    }
    public static String sha256(String input) {
        return hash(input, Algorithm.SHA256);
    }
    public static String sha512(String input) {
        return hash(input, Algorithm.SHA512);
    }
    public static void main(String[] args) {
        String text = "Hello World";
        System.out.println("MD5: " + md5(text));
        System.out.println("SHA-256: " + sha256(text));
        System.out.println("SHA-512: " + sha512(text));
        // 通用方法
        System.out.println("通用SHA-1: " + hash(text, Algorithm.SHA1));
    }
}

注意事项

1. MD5安全性: MD5已被证实存在碰撞问题，不建议用于安全敏感场景
2. SHA-256推荐: 对于大多数场景，推荐使用SHA-256
3. 加盐: 存储密码时一定要加盐，防止彩虹表攻击
4. 迭代哈希: 对于密码存储，建议使用PBKDF2、bcrypt或scrypt等专门的密码哈希算法
5. 编码问题: 注意字符串编码，建议使用 getBytes("UTF-8") 而不是默认编码

这些示例涵盖了Java中MD5和SHA加密的基本用法,你可以根据实际需求选择合适的实现方式。