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https://github.com/wololock/obj2tok

Small (5,5 KB) Java library that allows you to convert Java object to a String token.
https://github.com/wololock/obj2tok

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Small (5,5 KB) Java library that allows you to convert Java object to a String token.

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= obj2tok - tokenize any object you want



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This small (5,5 KB) library allows you to convert Java object to a String token.



== Requirements



* Java 1.8 (tested with OpenJDK and OracleJDK)

* Java Cryptography Extension (JCE) http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html[http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html]



== How it works?



*obj2tok* does 3 major things to convert object to a string token:



* It "stringifies" object in the first place (this operation has to be bidirectional)

* It encodes given string (default implementation provides static key AES cipher token coder)

* In the end it encodes encrypted bytes using Base64



The main purpose of this class is to provide a simple and straightforward API for tokenizing objects. The tokenizing algorithm supports symmetric encryption using secret key - only authority that creates a token is able to revert tokenization and get the object back.



== Example



Please take a look at this exemplary test case - https://github.com/wololock/obj2tok/blob/master/src/test/groovy/com/github/wololock/obj2tok/examples/TokenWithExpirationExampleSpec.groovy[https://github.com/wololock/obj2tok/blob/master/src/test/groovy/com/github/wololock/obj2tok/examples/TokenWithExpirationExampleSpec.groovy]



What it shows is an example of string tokenizing a class called `Token`:



[source,groovy]

----

class Token {

    String id

    LocalDateTime createdDate

    int ttl

    boolean expired(LocalDateTime now) {

        return now.isAfter(createdDate.plusHours(ttl))

    }

}

----



The purpose of this class is very simple - it describes a token that expires after a predefined amount of hours (`ttl` field). It contains `id` so the authority that creates the token knows what is the resource id it refers to.



The main class that does tokenization calls `Tokenizer`. It expects 2 dependencies injected by its constructor:



* A `TokenCoder` instance

* A `Stringifier` instance



As a `TokenCoder` we use `StaticKeyAESCipherTokenCoder` implementation which uses `AES` algorithm with static secret key. As a `Stringifier` we use `JacksonJSONStringifier` implementation that represents object as a JSON string. Keep in mind that these implementations are only exemplary - you can always implement these interfaces on your own and provide a different encoding and stringifying strategies.



Here is what our `TokenCoder` looks like in given example:



[source,groovy]

----

TokenCoder tokenCoder = new StaticKeyAESCipherTokenCoder("this_is_secret_key")

----



`Stringifier` uses predefined `ObjectMapper` that uses serializer and deserializer for `LocalDateTime` class:



[source,groovy]

----

Stringifier stringifier = new JacksonJSONStringifier(objectMapper)

----



Now, if our exemplary object stringifies to:



[source,json]

----

{"id":"72a12319-5d81-438f-bb0d-9ae0e430bfb2","createdDate":"2016-04-06T15:45:23","ttl":48}

----



then this is what its token representation looks like:



[source,text]

----

Nl9A3oBR/dyqXJLYweopbpqEwV9D/2kz5VTuxOhxLshC/muB3enTEVTCf/7pOFWWSQVgUs3JlCTm1lqou+UDqg7uaWUdhwUWl71nlgJ21PoaWBYVtLDniCpvfOlqC5OO

----



As a homework you can grab the token and pass it to the `Tokenizer.fromToken(token,type)` method that uses `TokenCoder` and `Stringifier` mentioned before and you will get back your Java object.



[source,groovy]

----

String tokenStr = "Nl9A3oBR/dyqXJLYweopbpqEwV9D/2kz5VTuxOhxLshC/muB3enTEVTCf/7pOFWWSQVgUs3JlCTm1lqou+UDqg7uaWUdhwUWl71nlgJ21PoaWBYVtLDniCpvfOlqC5OO";



Token token = tokenizer.fromToken(tokenStr, Token.class);



assert token.getId().equals("72a12319-5d81-438f-bb0d-9ae0e430bfb2");



assert token.getTtl() == 48;



assert token.getCreatedDate().equals(LocalDateTime.parse("2016-04-06T15:45:23"));



----



== Runtime dependencies



[source]

----

runtime - Runtime classpath for source set 'main'.

+--- com.fasterxml.jackson.core:jackson-databind:2.7.3

|    +--- com.fasterxml.jackson.core:jackson-annotations:2.7.0

|    \--- com.fasterxml.jackson.core:jackson-core:2.7.3

\--- org.slf4j:slf4j-api:1.7.21

----