Combined JOSE parsing

To parse arbitrary JOSE objects (plain, signed and encrypted) use the base JOSEObject class:

import com.nimbusds.jose.*;

JOSEObject joseObject;

try {
    joseObject = JOSEObject.parse(string);
} catch (ParseException e) {
    // Invalid JOSE object encoding
}

// Check type of the parsed JOSE object
if (joseObject instanceof PlainObject) {
    PlainObject plainObject = (PlainObject)joseObject;
    // continue processing of plain object...
} else if (joseObject instanceof JWSObject) {
    JWSObject jwsObject = (JWSObject)joseObject;
    // continue with signature verification...
} else if (joseObject instanceof JWEObject) {
    JWEObject jweObject = (JWEObject)joseObject;
    // continue with decryption...
}

Use the JOSEObjectHandler interface or its JOSEObjectAdapter to handle parser output in more elegant and type-safe way, with support for generics:

import com.nimbusds.jose.*;

// Devise a type-self handler for the expected JOSE objects which returns a
// string payload after verification / decryption
class Handler implements JOSEObjectHandler<String> {

    @Override
    public String onPlainObject(PlainObject plainObject) {
        return null; // Plain object payload not recognised
    }

    @Override
    public String onJWSObject(JWSObject jwsObject) {
        // Verify signature
        boolean success = jwsObject.verify(...);
        if (success) {
            // Return payload as string
            return jwsObject.getPayload().toString();
        } else {
            return null;
        }
    }

    @Override
    public String onJWEObject(JWEObject jweObject) {
        // Decrypt
        jweObject.decrypt(...);
        // Return payload after successful decryption
        return jweObject.getPayload().toString();
    }
}

// Parse JOSE objects
String content = JOSEObject.parse(string, new Handler(...));