java 如何生成rsa OAEPW填充模式得密钥 并保存 每次使用同一套进行加密解密

在Java中，可以使用Java Cryptography Architecture（JCA）提供的API来生成RSA密钥对并进行加密解密。下面是使用JCA生成RSA密钥对并进行加密解密并保存的示例代码：

import javax.crypto.Cipher;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.*;

public class RSAExample {
    private static final String ALGORITHM = "RSA";
    private static final String TRANSFORMATION = "RSA/ECB/OAEPWithSHA-256AndMGF1Padding";
    private static final int KEY_SIZE = 2048;

    private static final String PRIVATE_KEY_FILE = "private.key";
    private static final String PUBLIC_KEY_FILE = "public.key";

    public static void main(String[] args) throws Exception {
        // 生成密钥对
        KeyPair keyPair = generateKeyPair();

        // 明文
        String plainText = "Hello, world!";

        // 加密
        byte[] cipherText = encrypt(plainText.getBytes(), keyPair.getPublic());

        // 解密
        byte[] decryptedText = decrypt(cipherText, keyPair.getPrivate());

        // 输出结果
        System.out.println("Plain text: " + plainText);
        System.out.println("Cipher text: " + new String(cipherText));
        System.out.println("Decrypted text: " + new String(decryptedText));
    }

    // 生成密钥对并保存到文件
    public static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
        keyPairGenerator.initialize(KEY_SIZE);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        saveToFile(PRIVATE_KEY_FILE, keyPair.getPrivate().getEncoded());
        saveToFile(PUBLIC_KEY_FILE, keyPair.getPublic().getEncoded());
        return keyPair;
    }

    // 从文件中加载私钥
    public static PrivateKey loadPrivateKey() throws Exception {
        byte[] privateKeyBytes = Files.readAllBytes(Paths.get(PRIVATE_KEY_FILE));
        PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        return keyFactory.generatePrivate(privateKeySpec);
    }

    // 从文件中加载公钥
    public static PublicKey loadPublicKey() throws Exception {
        byte[] publicKeyBytes = Files.readAllBytes(Paths.get(PUBLIC_KEY_FILE));
        X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        return keyFactory.generatePublic(publicKeySpec);
    }

    // 加密
    public static byte[] encrypt(byte[] data, PublicKey publicKey) throws Exception {
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(data);
    }

    // 解密
    public static byte[] decrypt(byte[] data, PrivateKey privateKey) throws Exception {
        Cipher cipher = Cipher.getInstance(TRANSFORMATION);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    // 保存密钥到文件
    public static void saveToFile(String fileName, byte[] data) throws Exception {
        Files.write(Paths.get(fileName), data);
    }
}

在上面的示例代码中，使用`generateKeyPair`方法生成RSA密钥对，并将其保存到文件中。使用`loadPrivateKey`和`loadPublicKey`方法从文件中加载私钥和公钥。使用`encrypt`和`decrypt`方法进行加密和解密。使用`saveToFile`方法将密钥保存到文件中。

需要注意的是，生成的密钥对需要妥善保管，私钥不应该泄露给他人。此外，加密和解密时需要使用相同的填充模式和密钥对。