How to add users to AuthenticationManagerBuilder from a file?

Question

I am writing a Google Chrome extension that requires user authentication that I have set up with Spring, and currently I have a few example usernames and passwords in my code while I'm still developing. At this point, I am ready to add real usernames and passwords, but I want to be able to load them into an AuthenticationManagerBuilder object from an outside file.

Here is the relevant code so far:

@Autowired
public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
    auth
        .inMemoryAuthentication()   
            .withUser("user1").password("password1").roles("USER").and()
            .withUser("user2").password("password2").roles("USER").and()
            .withUser("user3").password("password3").roles("USER");
}

I want to be able to build the auth object instead from a file that would contain something like this:

user1    password1
user2    password2
user3    password3

How would I do this (if it is even possible)?

Answer 1

Use a UserDetailsService instead. Just read the file inside the loadUserByUsername(String username) method, if any user with the given username exists, return a UserDetails or User representing that user. Otherwise throw a UsernameNotFoundException exception:

@Autowired
public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
    // Read the file
    // Loop through all users and search for the given username
    // Return User or throw UsernameNotFoundException
    auth.userDetailsService(username -> {
            try {
                String pathToFile = // Path to file;
                List<String> users = Files.readAllLines(Paths.get(pathToFile));
                for (String user : users) {
                    String[] parts = user.split("\\s+", 2);
                    String theUsername = parts[0];
                    String password = parts[1];

                    if (username.equals(theUsername))
                        return new User(theUsername, password, Collections.singleton(new SimpleGrantedAuthority("USER")));
                }
                throw new UsernameNotFoundException("Invalid username");
            } catch (Exception e) {
                throw new UsernameNotFoundException("Invalid username");
            }
    });
}