shiro控制用户登录的验证原理

在前端输入用户名和密码，shiro是如何校验用户的信息完成登录的呢。

UsernamePasswordToken token = new UsernamePasswordToken(user.getUserName(), user.getUserPwd());
Subject subject = SecurityUtils.getSubject();
subject.login(token);
userVO = (UserVO) subject.getPrincipal();

上面有一行代码subject.login(token);
当使用该方法时，会找到接口interface Subject的login方法，实际是进入了subject接口的实现类DelegatingSubject中：

public void login(AuthenticationToken token) throws AuthenticationException {
        this.clearRunAsIdentitiesInternal();
        Subject subject = this.securityManager.login(this, token);
        String host = null;
        PrincipalCollection principals;
        if (subject instanceof DelegatingSubject) {
            DelegatingSubject delegating = (DelegatingSubject)subject;
            principals = delegating.principals;
            host = delegating.host;
        } else {
            principals = subject.getPrincipals();
        }

        if (principals != null && !principals.isEmpty()) {
            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 = this.decorate(session);
            } else {
                this.session = null;
            }

        } else {
            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);
        }
    }

执行该方法，当执行到Subject subject = this.securityManager.login(this, token)时，进入securityManager接口的实现类DefaultSecurityManager中：

public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info;
        try {
            info = this.authenticate(token);
        } catch (AuthenticationException var7) {
            AuthenticationException ae = var7;

            try {
                this.onFailedLogin(token, ae, subject);
            } catch (Exception var6) {
                if (log.isInfoEnabled()) {
                    log.info("onFailedLogin method threw an exception.  Logging and propagating original AuthenticationException.", var6);
                }
            }

            throw var7;
        }

        Subject loggedIn = this.createSubject(token, info, subject);
        this.onSuccessfulLogin(token, info, loggedIn);
        return loggedIn;
    }

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

执行方法info = this.authenticate(token), 顶层实现了Authenticator 接口:

Authenticator 接口以及实现类AbstractAuthenticator.class获取认证信息：

public interface Authenticator {
    AuthenticationInfo authenticate(AuthenticationToken var1) throws AuthenticationException;
}


//Authenticator接口的实现类 AbstractAuthenticator
public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
        if (token == null) {
            throw new IllegalArgumentException("Method argument (authentication token) cannot be null.");
        } else {
            log.trace("Authentication attempt received for token [{}]", token);

            AuthenticationInfo info;
            try {
                info = this.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 var8) {
                AuthenticationException ae = null;
                if (var8 instanceof AuthenticationException) {
                    ae = (AuthenticationException)var8;
                }

                if (ae == null) {
                    String msg = "Authentication failed for token submission [" + token + "].  Possible unexpected " + "error? (Typical or expected login exceptions should extend from AuthenticationException).";
                    ae = new AuthenticationException(msg, var8);
                    if (log.isWarnEnabled()) {
                        log.warn(msg, var8);
                    }
                }

                try {
                    this.notifyFailure(token, ae);
                } catch (Throwable var7) {
                    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, var7);
                    }
                }

                throw ae;
            }

            log.debug("Authentication successful for token [{}].  Returned account [{}]", token, info);
            this.notifySuccess(token, info);
            return info;
        }
    }

protected abstract AuthenticationInfo doAuthenticate(AuthenticationToken var1) throws AuthenticationException;

ModularRealmAuthenticator 继承AbstractAuthenticator，重写了方法doAuthenticate：

 protected AuthenticationInfo doAuthenticate(AuthenticationToken authenticationToken) throws AuthenticationException {
        this.assertRealmsConfigured();
        Collection realms = this.getRealms();
        return realms.size() == 1 ? this.doSingleRealmAuthentication((Realm)realms.iterator().next(), authenticationToken) : this.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);
        } else {
            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);
            } else {
                return info;
            }
        }
    }

AuthenticationInfo info = realm.getAuthenticationInfo(token)方法，追寻到Realm接口的实现类AuthenticatingRealm:

public final AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
        AuthenticationInfo info = this.getCachedAuthenticationInfo(token);
        if (info == null) {
            info = this.doGetAuthenticationInfo(token);
            log.debug("Looked up AuthenticationInfo [{}] from doGetAuthenticationInfo", info);
            if (token != null && info != null) {
                this.cacheAuthenticationInfoIfPossible(token, info);
            }
        } else {
            log.debug("Using cached authentication info [{}] to perform credentials matching.", info);
        }

        if (info != null) {
            this.assertCredentialsMatch(token, info);
        } else {
            log.debug("No AuthenticationInfo found for submitted AuthenticationToken [{}].  Returning null.", token);
        }

        return info;
    }

使用shiro认证真正主要我们写的就是获取认证数据，MyShiroRealm extends AuthorizingRealm，重写doGetAuthenticationInfo方法：

 /**
     * 认证信息.(身份验证) : Authentication 是用来验证用户身份
     */
    @Override
    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken authcToken) throws AuthenticationException {

        UsernamePasswordToken token = (UsernamePasswordToken) authcToken;
        String name = token.getUsername();

        // 从数据库获取对应用户名密码的用户
        R r = xxx.getUserByUserName(name);
        if (null == r || !r.get("code").toString().equals("200") || !r.containsKey("data") || null == r.get("data")) {
            throw new UnknownAccountException();
        }
        UserVO userVO = R.getData(r, UserVO.class);
        
        SimpleAuthenticationInfo authenticationInfo = new SimpleAuthenticationInfo(userVO, userVO.getUserPwd(), ByteSource.Util.bytes(userVO.getUserSalt()), getName());
            return authenticationInfo;
        }

        throw new UnknownAccountException();
    }

shiro对用户信息的校验完成，即用户合法，不会进行拦截，就会按照我们编辑的逻辑跳转至页面。