How to Resolve the 'No AuthenticationProvider Found for UsernamePasswordAuthenticationToken' Error

What does the error 'No AuthenticationProvider found for UsernamePasswordAuthenticationToken' mean and how can it be resolved?

public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.inMemoryAuthentication()
            .withUser("user").password(passwordEncoder().encode("password")).roles("USER");
    }
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests()
            .anyRequest().authenticated()
            .and().formLogin();
    }
}

The error 'No AuthenticationProvider found for UsernamePasswordAuthenticationToken' typically occurs in Spring Security when there is no configured AuthenticationProvider capable of handling the given authentication request. This commonly indicates that the security configuration is incomplete or misconfigured, resulting in the inability to handle authentication requests properly.

public class MyAuthenticationProvider implements AuthenticationProvider {
    @Override
    public Authentication authenticate(Authentication authentication) throws AuthenticationException {
        String username = authentication.getName();
        String password = authentication.getCredentials().toString();
        // Validate username and password against a user store
        return new UsernamePasswordAuthenticationToken(username, password, new ArrayList<>());
    }

    @Override
    public boolean supports(Class<?> authentication) {
        return authentication.equals(UsernamePasswordAuthenticationToken.class);
    }
}

Causes

• No AuthenticationProvider configured in the Spring Security context.
• The UsernamePasswordAuthenticationToken is not supported by any configured AuthenticationProvider.
• Configuration issues in the security setup that prevent the correct invocation of the authentication manager.

Solutions

• Ensure that an AuthenticationProvider is provided in your configuration, such as an InMemoryAuthentication or DaoAuthenticationProvider.
• Verify that the authentication configuration files or annotations are correctly implemented and that the context is loading them.
• Add a custom AuthenticationProvider if necessary, implementing the AuthenticationProvider interface or using provided classes.

Mistake: Not defining any AuthenticationProvider in the security configuration.

Solution: Make sure to include an AuthenticationProvider like InMemoryAuthentication or JdbcAuthentication.

Mistake: Forgetting to annotate the security configuration class with @EnableWebSecurity or equivalent.

Solution: Add @EnableWebSecurity to your configuration class to ensure that it is picked up by Spring.

Mistake: Incorrectly implementing the AuthenticationProvider interface leading to null return or exceptions.

Solution: Ensure your AuthenticationProvider correctly implements the authenticate method and handles authentication properly.