How to automatically login as a user using Spring Security without knowing their password?

Question

My application uses Spring Security, and my client requires:

• users to be able to automatically login after signup.
• an admin to login as any user without knowing their password.

So I need to figure out how to login as any user automatically without knowing their password.

How can this be accomplished using Spring Security?

Answer 1

for second problem

an admin to login as any user without knowing their password.

you should use switch user feature from spring. javadoc and article

Answer 2

To get this to work, I had to:

Configure a reference to the UserDetailsService (jdbcUserService)

<authentication-manager>
<authentication-provider>
<jdbc-user-service id="jdbcUserService" data-source-ref="dataSource"
  users-by-username-query="select username,password, enabled from users where username=?" 
  authorities-by-username-query="select u.username, ur.authority from users u, user_roles ur where u.user_id = ur.user_id and u.username =?  " 
/>
</authentication-provider>
</authentication-manager>

Autowire my userDetailsManager in my controller:

@Autowired
@Qualifier("jdbcUserService")  // <-- this references the bean id
public UserDetailsManager userDetailsManager;

In the same controller, authenticate my user like so:

@RequestMapping("/automatic/login/test")
public @ResponseBody String automaticLoginTest(HttpServletRequest request) 
{
    String username = "[email protected]";

    Boolean result = authenticateUserAndInitializeSessionByUsername(username, userDetailsManager, request);

    return result.toString();
}

public boolean authenticateUserAndInitializeSessionByUsername(String username, UserDetailsManager userDetailsManager, HttpServletRequest request)
{
    boolean result = true;

    try
    {
        // generate session if one doesn't exist
        request.getSession();

        // Authenticate the user
        UserDetails user = userDetailsManager.loadUserByUsername(username);
        Authentication auth = new UsernamePasswordAuthenticationToken(user, null, user.getAuthorities());
        SecurityContextHolder.getContext().setAuthentication(auth);
    }
    catch (Exception e)
    {
      System.out.println(e.getMessage());

      result = false;
    }

    return result;
}

Note that a good precursor to just using spring security for your app can be found here.