core/src/main/java/org/springframework/security/access/intercept/AbstractSecurityInterceptor.java
private Authentication authenticateIfRequired() {
		Authentication authentication = SecurityContextHolder.getContext()
				.getAuthentication();

		if (authentication.isAuthenticated() && !alwaysReauthenticate) {
			if (logger.isDebugEnabled()) {
				logger.debug("Previously Authenticated: " + authentication);
			}

			return authentication;
		}

		authentication = authenticationManager.authenticate(authentication);

		// We don't authenticated.setAuthentication(true), because each provider should do
		// that
		if (logger.isDebugEnabled()) {
			logger.debug("Successfully Authenticated: " + authentication);
		}

		SecurityContextHolder.getContext().setAuthentication(authentication);

		return authentication;
	}
private Authentication authenticateIfRequired() {
		Authentication authentication = SecurityContextHolder.getContext()
				.getAuthentication();

		if (authentication.isAuthenticated() && !alwaysReauthenticate) {
			if (logger.isDebugEnabled()) {
				logger.debug("Previously Authenticated: " + authentication);
			}

			return authentication;
		}

		authentication = authenticationManager.authenticate(authentication);

		// We don't authenticated.setAuthentication(true), because each provider should do
		// that
		if (logger.isDebugEnabled()) {
			logger.debug("Successfully Authenticated: " + authentication);
		}

		SecurityContextHolder.getContext().setAuthentication(authentication);

		return authentication;
	}
private Authentication authenticateIfRequired ( ) { Authentication authentication = SecurityContextHolder . getContext ( ) . getAuthentication ( ) ; if ( authentication . isAuthenticated ( ) && ! alwaysReauthenticate ) { if ( logger . isDebugEnabled ( ) ) { logger . debug ( "Previously Authenticated: " + authentication ) ; } return authentication ; } authentication = authenticationManager . authenticate ( authentication ) ; // We don't authenticated.setAuthentication(true), because each provider should do // that if ( logger . isDebugEnabled ( ) ) { logger . debug ( "Successfully Authenticated: " + authentication ) ; } SecurityContextHolder . getContext ( ) . setAuthentication ( authentication ) ; return authentication ; }
Checks the current authentication token and passes it to the AuthenticationManager
if {@link org.springframework.security.core.Authentication#isAuthenticated()}
returns false or the property <tt>alwaysReauthenticate</tt> has been set to true.

@return an authenticated <tt>Authentication</tt> object.
Checks the current authentication token and passes it to the AuthenticationManager if { @link org . springframework . security . core . Authentication#isAuthenticated () } returns false or the property <tt > alwaysReauthenticate< / tt > has been set to true .