auth.userDetailsService(userDetailsService).passwordEncoder(）

This is a method call in Spring Security configuration that sets the userDetailsService and passwordEncoder properties for authentication.

The userDetailsService is an interface that loads user-specific data, such as the user's username, password, and roles, from a persistent data store. The passwordEncoder is an interface that encrypts and compares passwords.

By setting these properties, Spring Security knows how to authenticate users and check their passwords.

For example:

@Autowired
private UserDetailsService userDetailsService;

@Bean
public DaoAuthenticationProvider authenticationProvider() {
  DaoAuthenticationProvider authProvider = new DaoAuthenticationProvider();
  authProvider.setUserDetailsService(userDetailsService);
  authProvider.setPasswordEncoder(new BCryptPasswordEncoder());
  return authProvider;
}

In this code snippet, the userDetailsService is injected using the @Autowired annotation, and a new instance of DaoAuthenticationProvider is created with the userDetailsService and a new BCryptPasswordEncoder. This allows Spring Security to authenticate users using the provided user details and encrypted passwords.