jjwt/changelog.md

## Release Notes

### 0.6.0

#### Enforce JWT Claims when Parsing

You can now enforce that JWT claims have expected values when parsing a compact JWT string.

For example, let's say that you require that the JWT you are parsing has a specific `sub` (subject) value,
otherwise you may not trust the token.  You can do that by using one of the `require` methods on the parser builder:

```java
try {
    Jwts.parser().requireSubject("jsmith").setSigningKey(key).parseClaimsJws(s);
} catch(InvalidClaimException ice) {
    // the sub field was missing or did not have a 'jsmith' value
}
```

If it is important to react to a missing vs an incorrect value, instead of catching `InvalidClaimException`, you can catch either `MissingClaimException` or `IncorrectClaimException`:

```java
try {
    Jwts.parser().requireSubject("jsmith").setSigningKey(key).parseClaimsJws(s);
} catch(MissingClaimException mce) {
    // the parsed JWT did not have the sub field
} catch(IncorrectClaimException ice) {
    // the parsed JWT had a sub field, but its value was not equal to 'jsmith'
}
```

You can also require custom fields by using the `require(fieldName, requiredFieldValue)` method - for example:

```java
try {
    Jwts.parser().require("myfield", "myRequiredValue").setSigningKey(key).parseClaimsJws(s);
} catch(InvalidClaimException ice) {
    // the 'myfield' field was missing or did not have a 'myRequiredValue' value
}
```
(or, again, you could catch either MissingClaimException or IncorrectClaimException instead)

#### Body Compression

**This feature is NOT JWT specification compliant**, *but it can be very useful when you parse your own tokens*.

If your JWT body is large and you have size restrictions (for example, if embedding a JWT in a URL and the URL must be under a certain length for legacy browsers or mail user agents), you may now compress the JWT body using a `CompressionCodec`:

```java
Jwts.builder().claim("foo", "someReallyLongDataString...")
    .compressWith(CompressionCodecs.DEFLATE) // or CompressionCodecs.GZIP
    .signWith(SignatureAlgorithm.HS256, key)
    .compact();
```

This will set a new `calg` header with the name of the compression algorithm used so that parsers can see that value and decompress accordingly.

The default parser implementation will automatically decompress DEFLATE or GZIP compressed bodies, so you don't need to set anything on the parser - it looks like normal:

```java
Jwts.parser().setSigningKey(key).parseClaimsJws(compact);
```

##### Custom Compression Algorithms

If the DEFLATE or GZIP algorithms are not sufficient for your needs, you can specify your own Compression algorithms by implementing the `CompressionCodec` interface and setting it on the parser:

```java
Jwts.builder().claim("foo", "someReallyLongDataString...")
    .compressWith(new MyCompressionCodec())
    .signWith(SignatureAlgorithm.HS256, key)
    .compact();
```

You will then need to specify a `CompressionCodecResolver` on the parser, so you can inspect the `calg` header and return your custom codec when discovered:

```java
Jwts.parser().setSigningKey(key)
    .setCompressionCodecResolver(new MyCustomCompressionCodecResolver())
    .parseClaimsJws(compact);
```

*NOTE*: Because body compression is not JWT specification compliant, you should only enable compression if both your JWT builder and parser are JJWT versions >= 0.6.0, or if you're using another library that implements the exact same functionality.  This feature is best reserved for your own use cases - where you both create and later parse the tokens.  It will likely cause problems if you compressed a token and expected a 3rd party (who doesn't use JJWT) to parse the token.

### 0.5.1

- Minor [bug](https://github.com/jwtk/jjwt/issues/31) fix [release](https://github.com/jwtk/jjwt/issues?q=milestone%3A0.5.1+is%3Aclosed) that ensures correct Base64 padding in Android runtimes.

### 0.5

- Android support! Android's built-in Base64 codec will be used if JJWT detects it is running in an Android environment.  Other than Base64, all other parts of JJWT were already Android-compliant.  Now it is fully compliant.

- Elliptic Curve signature algorithms!  `SignatureAlgorithm.ES256`, `ES384` and `ES512` are now supported.

- Super convenient key generation methods, so you don't have to worry how to do this safely:
  - `MacProvider.generateKey(); //or generateKey(SignatureAlgorithm)`
  - `RsaProvider.generateKeyPair(); //or generateKeyPair(sizeInBits)`
  - `EllipticCurveProvider.generateKeyPair(); //or generateKeyPair(SignatureAlgorithm)`

  The `generate`* methods that accept an `SignatureAlgorithm` argument know to generate a key of sufficient strength that reflects the specified algorithm strength.

Please see the full [0.5 closed issues list](https://github.com/jwtk/jjwt/issues?q=milestone%3A0.5+is%3Aclosed) for more information.

### 0.

- [Issue 8](https://github.com/jwtk/jjwt/issues/8): Add ability to find signing key by inspecting the JWS values before verifying the signature.

This is a handy little feature.  If you need to parse a signed JWT (a JWS) and you don't know which signing key was used to sign it, you can now use the new `SigningKeyResolver` concept.

A `SigningKeyresolver` can inspect the JWS header and body (Claims or String) _before_ the JWS signature is verified. By inspecting the data, you can find the key and return it, and the parser will use the returned key to validate the signature.  For example:

```java
SigningKeyResolver resolver = new MySigningKeyResolver();

Jws<Claims> jws = Jwts.parser().setSigningKeyResolver(resolver).parseClaimsJws(compact);
```

The signature is still validated, and the JWT instance will still not be returned if the jwt string is invalid, as expected.  You just get to 'see' the JWT data for key discovery before the parser validates.  Nice.

This of course requires that you put some sort of information in the JWS when you create it so that your `SigningKeyResolver` implementation can look at it later and look up the key.  The *standard* way to do this is to use the JWS `kid` ('key id') field, for example:

```java
Jwts.builder().setHeaderParam("kid", your_signing_key_id_NOT_THE_SECRET).build();
```

You could of course set any other header parameter or claims parameter instead of setting `kid` if you want - that's just the default field reserved for signing key identification.  If you can locate the signing key based on other information in the header or claims, you don't need to set the `kid` field - just make sure your resolver implementation knows how to look up the key.

Finally, a nice `SigningKeyResolverAdapter` is provided to allow you to write quick and simple subclasses or anonymous classes instead of having to implement the `SigningKeyResolver` interface directly.  For example:

```java
Jws<Claims> jws = Jwts.parser().setSigningKeyResolver(new SigningKeyResolverAdapter() {
        @Override
        public byte[] resolveSigningKeyBytes(JwsHeader header, Claims claims) {
            //inspect the header or claims, lookup and return the signing key
            String keyId = header.getKeyId(); //or any other field that you need to inspect
            return getSigningKey(keyId); //implement me
        }})
    .parseClaimsJws(compact);
```

### 0.3

- [Issue 6](https://github.com/jwtk/jjwt/issues/6): Parsing an expired Claims JWT or JWS (as determined by the `exp` claims field) will now throw an `ExpiredJwtException`.
- [Issue 7](https://github.com/jwtk/jjwt/issues/7): Parsing a premature Claims JWT or JWS (as determined by the `nbf` claims field) will now throw a `PrematureJwtException`.

### 0.2

#### More convenient Claims building

This release adds convenience methods to the `JwtBuilder` interface so you can set claims directly on the builder without having to create a separate Claims instance/builder, reducing the amount of code you have to write.  For example, this:

```java
Claims claims = Jwts.claims().setSubject("Joe");

String compactJwt = Jwts.builder().setClaims(claims).signWith(HS256, key).compact();
```

can now be written as:

```java
String compactJwt = Jwts.builder().setSubject("Joe").signWith(HS256, key).compact();
```

A Claims instance based on the specified claims will be created and set as the JWT's payload automatically.

#### Type-safe handling for JWT and JWS with generics

The following < 0.2 code produced a JWT as expected:

```java
Jwt jwt = Jwts.parser().setSigningKey(key).parse(compact);
```

But you couldn't easily determine if the `jwt` was a `JWT` or `JWS` instance or if the body was a `Claims` instance or a plaintext `String` without resorting to a bunch of yucky `instanceof` checks.  In 0.2, we introduce the `JwtHandler` when you don't know the exact format of the compact JWT string ahead of time, and parsing convenience methods when you do.

##### JwtHandler

If you do not know the format of the compact JWT string at the time you try to parse it, you can determine what type it is after parsing by providing a `JwtHandler` instance to the `JwtParser` with the new `parse(String compactJwt, JwtHandler handler)` method.  For example:

```java
T returnVal = Jwts.parser().setSigningKey(key).parse(compact, new JwtHandler<T>() {
    @Override
    public T onPlaintextJwt(Jwt<Header, String> jwt) {
        //the JWT parsed was an unsigned plaintext JWT
        //inspect it, then return an instance of T (see returnVal above)
    }

    @Override
    public T onClaimsJwt(Jwt<Header, Claims> jwt) {
        //the JWT parsed was an unsigned Claims JWT
        //inspect it, then return an instance of T (see returnVal above)
    }

    @Override
    public T onPlaintextJws(Jws<String> jws) {
        //the JWT parsed was a signed plaintext JWS
        //inspect it, then return an instance of T (see returnVal above)
    }

    @Override
    public T onClaimsJws(Jws<Claims> jws) {
        //the JWT parsed was a signed Claims JWS
        //inspect it, then return an instance of T (see returnVal above)
    }
});
```

Of course, if you know you'll only have to parse a subset of the above, you can use the `JwtHandlerAdapter` and implement only the methods you need.  For example:

```java
T returnVal = Jwts.parser().setSigningKey(key).parse(plaintextJwt, new JwtHandlerAdapter<Jwt<Header, T>>() {
    @Override
    public T onPlaintextJws(Jws<String> jws) {
        //the JWT parsed was a signed plaintext JWS
        //inspect it, then return an instance of T (see returnVal above)
    }

    @Override
    public T onClaimsJws(Jws<Claims> jws) {
        //the JWT parsed was a signed Claims JWS
        //inspect it, then return an instance of T (see returnVal above)
    }
});
```

##### Known Type convenience parse methods

If, unlike above, you are confident of the compact string format and know which type of JWT or JWS it will produce, you can just use one of the 4 new convenience parsing methods to get exactly the type of JWT or JWS you know exists.  For example:

```java

//for a known plaintext jwt string:
Jwt<Header,String> jwt = Jwts.parser().parsePlaintextJwt(compact);

//for a known Claims JWT string:
Jwt<Header,Claims> jwt = Jwts.parser().parseClaimsJwt(compact);

//for a known signed plaintext JWT (aka a plaintext JWS):
Jws<String> jws = Jwts.parser().setSigningKey(key).parsePlaintextJws(compact);

//for a known signed Claims JWT (aka a Claims JWS):
Jws<Claims> jws = Jwts.parser().setSigningKey(key).parseClaimsJws(compact);

```

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