adding component to fetch authenticated user-id

src/main/java/com/behl/flare/filter/JwtAuthenticationFilter.java

@@ -1,5 +1,7 @@
 package com.behl.flare.filter;
 
+import java.util.Optional;
+
 import org.apache.commons.lang3.StringUtils;
 import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
 import org.springframework.security.core.context.SecurityContextHolder;
@@ -25,6 +27,7 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
 
 	private static final String AUTHORIZATION_HEADER = "Authorization";
 	private static final String BEARER_PREFIX = "Bearer ";
+	private static final String USER_ID_CLAIM = "user_id";
 
 	@Override
 	@SneakyThrows
@@ -37,9 +40,9 @@ protected void doFilterInternal(HttpServletRequest request, HttpServletResponse
 			if (StringUtils.isNotEmpty(authorizationHeader) && authorizationHeader.startsWith(BEARER_PREFIX) ) {
 				final var token = authorizationHeader.replace(BEARER_PREFIX, StringUtils.EMPTY);
 				final var firebaseToken = firebaseAuth.verifyIdToken(token);
-				final var emailId = firebaseToken.getEmail();
+				final var userId = Optional.ofNullable(firebaseToken.getClaims().get(USER_ID_CLAIM)).orElseThrow(IllegalStateException::new);
 
-				final var authentication = new UsernamePasswordAuthenticationToken(emailId, null, null);
+				final var authentication = new UsernamePasswordAuthenticationToken(userId, null, null);
 				authentication.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
 				SecurityContextHolder.getContext().setAuthentication(authentication);
 			} 

src/main/java/com/behl/flare/utility/AuthenticatedUserIdProvider.java

@@ -0,0 +1,20 @@
+package com.behl.flare.utility;
+
+import java.util.Optional;
+
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.stereotype.Component;
+
+@Component
+public class AuthenticatedUserIdProvider {
+
+	public String getUserId() {
+		return Optional.ofNullable(SecurityContextHolder.getContext().getAuthentication())
+		        .map(Authentication::getPrincipal)
+		        .filter(String.class::isInstance)
+		        .map(String.class::cast)
+		        .orElseThrow(IllegalStateException::new);
+	}
+
+}