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AutorefreshingJwtAuthTokenGenerator.java
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AutorefreshingJwtAuthTokenGenerator.java
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package uk.gov.hmcts.reform.authorisation.generators;
import com.auth0.jwt.JWT;
import com.auth0.jwt.exceptions.JWTDecodeException;
import com.auth0.jwt.interfaces.DecodedJWT;
import uk.gov.hmcts.reform.authorisation.exceptions.JwtDecodingException;
import java.time.Duration;
import java.util.Date;
import static java.time.Instant.now;
/**
* Caches the JWT token and refreshes it once it expired.
*/
public class AutorefreshingJwtAuthTokenGenerator implements AuthTokenGenerator {
private final AuthTokenGenerator generator;
private final Duration refreshTimeDelta;
private DecodedJWT jwt;
/**
* Constructor.
*
* @param generator Token generator for automatic refresh
* @param refreshTimeDelta Time before actual expiry date in JWT when a new token should be requested.
*/
public AutorefreshingJwtAuthTokenGenerator(
AuthTokenGenerator generator,
Duration refreshTimeDelta
) {
this.generator = generator;
this.refreshTimeDelta = refreshTimeDelta;
}
public AutorefreshingJwtAuthTokenGenerator(AuthTokenGenerator generator) {
this(generator, Duration.ZERO);
}
@Override
public String generate() {
if (jwt == null || needToRefresh(jwt.getExpiresAt())) {
String newToken = generator.generate();
try {
jwt = JWT.decode(newToken);
} catch (JWTDecodeException exc) {
throw new JwtDecodingException(exc.getMessage(), exc);
}
}
return jwt.getToken();
}
private boolean needToRefresh(Date expDate) {
return expDate != null && Date.from(now().plus(refreshTimeDelta)).after(expDate);
}
}