@Controller
@Slf4j
public class LoginController {
	@RequestMapping("/login")
	public String login(User user) {
		if (StringUtils.isEmpty(user.getUserName()) || StringUtils.isEmpty(user.getPassword())) {
			return "error";
		}
		//用戶認證信息
		Subject subject = SecurityUtils.getSubject();
		UsernamePasswordToken usernamePasswordToken = new UsernamePasswordToken(
				user.getUserName(),
				user.getPassword());
		usernamePasswordToken.setRememberMe(true);
		try {
			//進行驗證，這里可以捕獲異常，然后返回對應信息
			subject.login(usernamePasswordToken);
		} catch (UnknownAccountException e) {
			log.error("用戶名不存在！", e);
			return "error";
		} catch (AuthenticationException e) {
			log.error("賬號或密碼錯誤！", e);
			return "error";
		} catch (AuthorizationException e) {
			log.error("沒有權限！", e);
			return "error";
		}
		return "shiro_index";
	}
}

 public void login(AuthenticationToken token) throws AuthenticationException {
        clearRunAsIdentitiesInternal();
        // 主要是這塊的方法
        Subject subject = securityManager.login(this, token);
        PrincipalCollection principals;
        String host = null;
        if (subject instanceof DelegatingSubject) {
            DelegatingSubject delegating = (DelegatingSubject) subject;
            //we have to do this in case there are assumed identities - we don't want to lose the 'real' principals:
            principals = delegating.principals;
            host = delegating.host;
        } else {
            principals = subject.getPrincipals();
        }
        if (principals == null || principals.isEmpty()) {
            String msg = "Principals returned from securityManager.login( token ) returned a null or " +
                    "empty value.  This value must be non null and populated with one or more elements.";
            throw new IllegalStateException(msg);
        }
        this.principals = principals;
        this.authenticated = true;
        if (token instanceof HostAuthenticationToken) {
            host = ((HostAuthenticationToken) token).getHost();
        }
        if (host != null) {
            this.host = host;
        }
        Session session = subject.getSession(false);
        if (session != null) {
            this.session = decorate(session);
        } else {
            this.session = null;
        }
    }

public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info;
        try {
            // 主要是這塊的方法
            info = authenticate(token);
        } catch (AuthenticationException ae) {
            try {
                onFailedLogin(token, ae, subject);
            } catch (Exception e) {
                if (log.isInfoEnabled()) {
                    log.info("onFailedLogin method threw an " +
                            "exception.  Logging and propagating original AuthenticationException.", e);
                }
            }
            throw ae; //propagate
        }
        Subject loggedIn = createSubject(token, info, subject);
        onSuccessfulLogin(token, info, loggedIn);
        return loggedIn;
    }

 public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
        return this.authenticator.authenticate(token);
    }

 public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
        if (token == null) {
            throw new IllegalArgumentException("Method argument (authentication token) cannot be null.");
        }
        log.trace("Authentication attempt received for token [{}]", token);
        AuthenticationInfo info;
        try {
            // 主要看這塊的代碼
            info = doAuthenticate(token);
            if (info == null) {
                String msg = "No account information found for authentication token [" + token + "] by this " +
                        "Authenticator instance.  Please check that it is configured correctly.";
                throw new AuthenticationException(msg);
            }
        } catch (Throwable t) {
            AuthenticationException ae = null;
            if (t instanceof AuthenticationException) {
                ae = (AuthenticationException) t;
            }
            if (ae == null) {
                //Exception thrown was not an expected AuthenticationException.  Therefore it is probably a little more
                //severe or unexpected.  So, wrap in an AuthenticationException, log to warn, and propagate:
                String msg = "Authentication failed for token submission [" + token + "].  Possible unexpected " +
                        "error? (Typical or expected login exceptions should extend from AuthenticationException).";
                ae = new AuthenticationException(msg, t);
                if (log.isWarnEnabled())
                    log.warn(msg, t);
            }
            try {
                notifyFailure(token, ae);
            } catch (Throwable t2) {
                if (log.isWarnEnabled()) {
                    String msg = "Unable to send notification for failed authentication attempt - listener error?.  " +
                            "Please check your AuthenticationListener implementation(s).  Logging sending exception " +
                            "and propagating original AuthenticationException instead...";
                    log.warn(msg, t2);
                }
            }
            throw ae;
        }
        log.debug("Authentication successful for token [{}].  Returned account [{}]", token, info);
        notifySuccess(token, info);
        return info;
    }

  protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException {
        assertRealmsConfigured();
        Collection<Realm> realms = getRealms();
        if (realms.size() == 1) {
            return doSingleRealmAuthentication(realms.iterator().next(), authenticationToken);
        } else {
            return doMultiRealmAuthentication(realms, authenticationToken);
        }
    }

 protected AuthenticationInfo doSingleRealmAuthentication(Realm realm, AuthenticationToken token) {
        if (!realm.supports(token)) {
            String msg = "Realm [" + realm + "] does not support authentication token [" +
                    token + "].  Please ensure that the appropriate Realm implementation is " +
                    "configured correctly or that the realm accepts AuthenticationTokens of this type.";
            throw new UnsupportedTokenException(msg);
        }
        AuthenticationInfo info = realm.getAuthenticationInfo(token);
        if (info == null) {
            String msg = "Realm [" + realm + "] was unable to find account data for the " +
                    "submitted AuthenticationToken [" + token + "].";
            throw new UnknownAccountException(msg);
        }
        return info;
    }

 public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info = getCachedAuthenticationInfo(token);
        if (info == null) {
            //otherwise not cached, perform the lookup:
            info = doGetAuthenticationInfo(token);
            log.debug("Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo", info);
            if (token != null && info != null) {
                cacheAuthenticationInfoIfPossible(token, info);
            }
        } else {
            log.debug("Using cached authentication info [{}] to perform credentials matching.", info);
        }
        if (info != null) {
            assertCredentialsMatch(token, info);
        } else {
            log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
        }
        return info;
    }

protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken authenticationToken) throws AuthenticationException {
		if(StringUtils.isEmpty(authenticationToken.getPrincipal())) {
			return null;
		}
		// 獲取用戶信息
		String userName = authenticationToken.getPrincipal().toString();
		User user = userService.selectByUserName(userName);
		// 用戶是否存在
		if(user == null) {
			throw new UnknownAccountException();
		}
		// 是否激活
		if(user !=null && user.getStatus().equals("0")){
			throw new  DisabledAccountException();
		}
		// 是否鎖定
		if(user!=null && user.getStatus().equals("3")){
			throw new  LockedAccountException();
		}
		// 若存在將此用戶存放到登錄認證info中，無需做密碼比對shiro會為我們進行密碼比對校驗
		if(user !=null && user.getStatus().equals("1")){
			ByteSource credentialsSalt = ByteSource.Util.bytes(user.getUserName()+ "salt");
			/** 這里驗證authenticationToken和simpleAuthenticationInfo的信息，構造方法支持三個或者四個參數，
			*	第一個參數傳入userName或者是user對象都可以。
			*	第二個參數傳入數據庫中該用戶的密碼（記得是加密后的密碼）
			*	第三個參數傳入加密的鹽值，若沒有則可以不加
			*	第四個參數傳入當前Relam的名字
			**/
			SimpleAuthenticationInfo simpleAuthenticationInfo = new SimpleAuthenticationInfo(userName, user.getPassword().toString(),credentialsSalt, getName());
			return simpleAuthenticationInfo;
		}
		return null;
	}

 public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info = getCachedAuthenticationInfo(token);
        if (info == null) {
            //otherwise not cached, perform the lookup:
            info = doGetAuthenticationInfo(token);
            log.debug("Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo", info);
            if (token != null && info != null) {
                cacheAuthenticationInfoIfPossible(token, info);
            }
        } else {
            log.debug("Using cached authentication info [{}] to perform credentials matching.", info);
        }
        if (info != null) {
            // 進行密碼匹配
            assertCredentialsMatch(token, info);
        } else {
            log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
        }
        return info;
    }

protected void assertCredentialsMatch(AuthenticationToken token, AuthenticationInfo info) throws AuthenticationException {
        CredentialsMatcher cm = getCredentialsMatcher();
        if (cm != null) {
            if (!cm.doCredentialsMatch(token, info)) {
                //not successful - throw an exception to indicate this:
                String msg = "Submitted credentials for token [" + token + "] did not match the expected credentials.";
                throw new IncorrectCredentialsException(msg);
            }
        } else {
            throw new AuthenticationException("A CredentialsMatcher must be configured in order to verify " +
                    "credentials during authentication.  If you do not wish for credentials to be examined, you " +
                    "can configure an " + AllowAllCredentialsMatcher.class.getName() + " instance.");
        }
    }

public boolean doCredentialsMatch(AuthenticationToken token, AuthenticationInfo info) {
        Object tokenHashedCredentials = hashProvidedCredentials(token, info);
        Object accountCredentials = getCredentials(info);
        return equals(tokenHashedCredentials, accountCredentials);
    }