How to Deserialize String to Java Object

Question

I try to deserialize String to Java Object from a Redis server which is used to store Spring sessions, and I want to deserialize it outside of the Spring framework. I think the Spring Redis serializer is probably using the default charset, UTF-8, to serialize Java Object to String.

The String in Redis:

\xAC\xED\x00\x05sr\x00\x0Ejava.lang.Long;\x8B\xE4\x90\xCC\x8F#\xDF\x02\x00\x01J\x00\x05valuexr\x00\x10java.lang.Number\x86\xAC\x95\x1D\x0B\x94\xE0\x8B\x02\x00\x00xp\x00\x00\x00\x00\x00\x00\xD7

The method I use:

private static void scanKeys(Jedis jedis, String prefix, String hashKey)
        throws IOException, ClassNotFoundException {
    Set<String> keys = jedis.keys(prefix + "*");

    for (String key : keys) {
        if (!key.contains("expir")) {
            Map<String, String> sessionMap = jedis.hgetAll(key);

            for (Entry<String, String> entry : sessionMap.entrySet()) {

                if (entry.getValue() != null && entry.getKey().equals(hashKey)) {
                    System.out.println(entry.getKey());
                    System.out.println(entry.getValue());

                    byte[] output = entry.getValue().getBytes(charset);
                    System.out.println(Arrays.toString(output));    
                    try {
                        Long id = (Long) deserialize(output);
                        System.out.println(id);
                    } catch (EOFException e) {
                        break;
                    }
                }
            }

        }

    }
}

public static Object deserialize(byte[] data) throws IOException, ClassNotFoundException {
    ByteArrayInputStream in = new ByteArrayInputStream(data);
    ObjectInputStream is = new ObjectInputStream(in);
    return is.readObject();
}

The error message:

java.io.StreamCorruptedException: invalid stream header: EFBFBDEF
    at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:862)
    at java.io.ObjectInputStream.<init>(ObjectInputStream.java:354)
    at practice.redis.jedis.App.deserialize(App.java:191)
    at practice.redis.jedis.App.scanKeys(App.java:168)
    at practice.redis.jedis.App.main(App.java:77)

I know the conversion between byte[] and String with UTF-8 is probably where the problem is, but I still want to ask if anyone knows how to solve this problem without modifying the serialization part.

ᴇʟᴇvᴀтᴇ ᴇʟᴇvᴀтᴇ · Accepted Answer · 2018-05-22T18:24:19

I would suggest you parse the string yourself. It looks like it's a simple sequence of escaped and unescaped bytes.

String value = "\\xAC\\xED\\x00\\x05sr\\x00\\x0Ejava.lang.Long;\\x8B\\xE4\\x90\\xCC\\x8F#\\xDF\\x02\\x00\\x01J\\x00\\x05valuexr\\x00\\x10java.lang.Number\\x86\\xAC\\x95\\x1D\\x0B\\x94\\xE0\\x8B\\x02\\x00\\x00xp\\x00\\x00\\x00\\x00\\x00\\x00\\xD7";

try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
    int i = 0;
    while (i < value.length()) {
        char ch = value.charAt(i);
        if (ch == '\\') {
            if (value.charAt(i + 1) != 'x') {
                throw new UnsupportedOperationException();
            }
            String hex = value.substring(i + 2, i + 4);
            byteArrayOutputStream.write(Integer.parseInt(hex, 16) & 0xFF);
            i += 4;
        } else {
            byteArrayOutputStream.write(ch);
            i++;
        }
    }

    byte[] output = byteArrayOutputStream.toByteArray();
    Long id = (Long) deserialize(output);
    System.out.println(id);
}

How to Deserialize String to Java Object

1 Answers