shiro学习笔记-Subject#login(token)实现过程

本博文所有的代码均为shiro官网（http://shiro.apache.org/）中shiro 1.3.2版本中的源码。

追踪Subject的login(AuthenticationToken token)方法，其调用的为DelegatingSubject类的login方法，DelegatingSubject实现了Subject接口，DelegatingSubject#login如下：

 public void login(AuthenticationToken token) throws AuthenticationException {
     clearRunAsIdentitiesInternal();
     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;
     }
 }

在上面代码的第三行：Subject subject = securityManager.login(this, token); 注意到其调用了SecurityManager的login方法，SecurityManager为接口，实际上调用的其实现类DefaultSecurityManager的login方法，方法如下：

 public Subject login(Subject subject, AuthenticationToken token) throws AuthenticationException {
     AuthenticationInfo info;
     try {
         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;
 }

在上面代码第四行：info = authenticate(token); 继续跟踪，发现authenticate(AuthenticationToken token);方法为DefaultSecurityManager的父类AuthenticatingSecurityManager的方法，AuthenticatingSecurityManager#authenticate方法如下：

 public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
     return this.authenticator.authenticate(token);
3 }

authenticator为Authenticator接口，继续跟踪，AbstractAuthenticator抽象类实现了Authenticator接口，接下来继续查看AbstractAuthenticator#authenticate(token);方法：

 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 {
         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;
 }

上面代码第11行：info = doAuthenticate(token); 这个方法为ModularRealmAuthticator类中的方法，因为ModularRealmAuthticator继承了AbstractAuthenticator抽象类。另外，要注意第12行-第16行，如果info==null，就会抛出异常。ModularRealmAuthticator的doAuthenticate(token);方法如下：

 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);
     }
 }

这里，我们关注上面第五行代码：doSingleRealmAuthentication(realms.iterator().next(), authenticationToken); else语句中的doMultiRealmAuthentication(realms, authenticationToken);类似。跟踪到doSingleRealmAuthentication方法如下：

 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;
 }

上面代码第八行：AuthenticationInfo info = realm.getAuthenticationInfo(token); realm为Realm接口，实际上调用的是其实现类AuthenticatingRealm中的getAuthenticationInfo方法，方法如下：

 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;
 }

上面代码第三行：AuthenticationInfo info = getCachedAuthenticationInfo(token);从缓存中获取认证信息，如果未获取到，则调用第六行的doGetAuthenticationInfo(token); 方法获取认证信息。继续跟踪，发现有几个类实现了该方法，如下图所示：

最后，附上SecurityManager和Realm等的类关系图：

Realm：

SecurityManager:

Authenticator: