在j_security表单的另一边调用用户名？

// 在登录成功后的代码中
String username = request.getParameter("j_username");
session.setAttribute("username", username);

String username = (String) session.getAttribute("username");

Principal principal = request.getUserPrincipal();
if (principal != null) {
    String username = principal.getName();
}

@Autowired
private AuthenticationManager authenticationManager;

public void someMethod() {
    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
    if (authentication != null && authentication.getPrincipal() instanceof UserDetails) {
        String username = ((UserDetails) authentication.getPrincipal()).getUsername();
    }
}

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
                .antMatchers("/login").permitAll()
                .anyRequest().authenticated()
                .and()
            .formLogin()
                .loginPage("/login")
                .defaultSuccessUrl("/home")
                .permitAll()
                .and()
            .logout()
                .permitAll();
    }

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
        auth.inMemoryAuthentication()
            .withUser("user").password("{noop}password").roles("USER");
    }
}