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：

1 public AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {
2     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 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: