罐子不同，但他们不应该答案

【问题标题】：Jar differs but they should not罐子不同，但他们不应该
【发布时间】：2019-11-22 19:38:26
【问题描述】：

我有一种创建 jar 的方法。

public class Test {

    public static void main(String[] args) throws Exception {
        aha();
        aha();
        aha();
        aha();
        Thread.sleep(5000);
        aha();
    }

    private static void aha() throws IOException, NoSuchAlgorithmException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        JarOutputStream jos = new JarOutputStream(baos);
        jos.putNextEntry(new ZipEntry("sd"));
        jos.write("sdf".getBytes());
        jos.close();
        MessageDigest md = MessageDigest.getInstance("sha1");
        byte[] digest = md.digest(baos.toByteArray());
        for (byte b : digest) {
            System.out.print("," + b);
        }
        System.out.println();
    }
}

输出是：

,-57,-44,59,113,-126,-15,71,62,-90,-120,27,36,-3,69,26,-55,63,107,-93,102
,-57,-44,59,113,-126,-15,71,62,-90,-120,27,36,-3,69,26,-55,63,107,-93,102
,-57,-44,59,113,-126,-15,71,62,-90,-120,27,36,-3,69,26,-55,63,107,-93,102
,-57,-44,59,113,-126,-15,71,62,-90,-120,27,36,-3,69,26,-55,63,107,-93,102
,-124,-26,-79,-28,-34,77,-72,83,92,53,30,-13,95,21,-92,55,70,24,-72,39

我需要相同的摘要，但最后一个摘要不同。如何成为可重现的哈希？

【问题讨论】：

标签： java jar sha1

【解决方案1】：

虽然几乎不可见，但如果您将ZipEntry 写入JarOutputStream，则底层ZipOutputStream 将为您初始化最后修改时间。

if (e.xdostime == -1) {
    // by default, do NOT use extended timestamps in extra
    // data, for now.
    e.setTime(System.currentTimeMillis());
}

您必须手动初始化时间，setTime 才能获得恒定的结果。

【讨论】：