在Java中安全加载Google OAuth2 JWT签名私钥的教程

File privKeyFile = new File(keyPath);

BufferedInputStream bis = new BufferedInputStream(new FileInputStream(privKeyFile));

byte[] privKeyBytes = new byte[8192];

bis.read(privKeyBytes);

bis.close();

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PKCS8EncodedKeySpec ks = new PKCS8EncodedKeySpec(privKeyBytes);

RSAPrivateKey privateKey = (RSAPrivateKey) keyFactory.generatePrivate(ks);

-----BEGIN PRIVATE KEY-----

MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDE...

...

-----END PRIVATE KEY-----

import java.io.File;

import java.nio.charset.StandardCharsets;

import java.nio.file.Files;

import java.security.KeyFactory;

import java.security.interfaces.RSAPrivateKey;

import java.security.spec.PKCS8EncodedKeySpec;

import org.apache.commons.codec.binary.Base64; // 或使用 java.util.Base64 (Java 8+)

public class PrivateKeyLoader {

    public RSAPrivateKey readPrivateKey(File file) throws Exception {

        // 1. 读取文件内容为字符串

        String keyContent = new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);

        // 2. 移除PEM头部和尾部

        // 3. 移除所有换行符

        String privateKeyPEM = keyContent

                .replace("-----BEGIN PRIVATE KEY-----", "")

                .replace("-----END PRIVATE KEY-----", "")

                .replaceAll(System.lineSeparator(), ""); // 兼容不同操作系统的换行符

        // 4. Base64解码

        // 注意：这里使用 Apache Commons Codec 的 Base64，

        // 如果是 Java 8 及更高版本，可以使用 java.util.Base64

        byte[] encoded = Base64.decodeBase64(privateKeyPEM);

        // 对于 Java 8+：

        // byte[] encoded = java.util.Base64.getDecoder().decode(privateKeyPEM);

        // 5. 构建PKCS8EncodedKeySpec

        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);

        // 6. 生成RSAPrivateKey

        KeyFactory keyFactory = KeyFactory.getInstance("RSA");

        return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);

    }

    public static void main(String[] args) {

        // 假设您的私钥文件名为 myprivatekey.pem

        File privateKeyFile = new File("myprivatekey.pem");

        PrivateKeyLoader loader = new PrivateKeyLoader();

        try {

            RSAPrivateKey privateKey = loader.readPrivateKey(privateKeyFile);

            System.out.println("私钥加载成功！算法: " + privateKey.getAlgorithm());

            // 此时 privateKey 即可用于 JWT 签名

        } catch (Exception e) {

            System.err.println("加载私钥失败: " + e.getMessage());

            e.printStackTrace();

        }

    }

}