shiro源码分析（一）入门

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shiro源码分析

shiro

最近闲来无事，准备读个框架源码，经别人推荐shiro，那就准备读读其中的设计。开涛大神已经有了跟我学Shiro系列，那我就跟着这个系列入门然后再深入源代码，所以我的侧重点就是源码分析。

话不多说，上开涛大神的入门案例地址http://jinnianshilongnian.iteye.com/blog/2019547：

@Test  
	public void testHelloworld() {  
	    //1、获取SecurityManager工厂，此处使用Ini配置文件初始化SecurityManager  
	    Factory<org.apache.shiro.mgt.SecurityManager> factory =  
	            new IniSecurityManagerFactory("classpath:shiro.ini");  
	    //2、得到SecurityManager实例 并绑定给SecurityUtils  
	    org.apache.shiro.mgt.SecurityManager securityManager = factory.getInstance();  
	    SecurityUtils.setSecurityManager(securityManager);  
	    //3、得到Subject及创建用户名/密码身份验证Token（即用户身份/凭证）  
	    Subject subject = SecurityUtils.getSubject();  
	    UsernamePasswordToken token = new UsernamePasswordToken("zhang", "123232");  
	  
	    try {  
	        //4、登录，即身份验证  
	        subject.login(token);  
	    } catch (AuthenticationException e) {  
	        //5、身份验证失败  
	    }  
	  
	    Assert.assertEquals(true, subject.isAuthenticated()); //断言用户已经登录  
	  
	    //6、退出  
	    subject.logout();  
	}

1：使用工厂模式来得到SecurityManager，由于可以通过不同工厂创建出不同的SecurityManager，如通过配置文件的形式来创建的IniSecurityManagerFactory工厂。类图如下：

Factory接口：通过泛型定义了一个T getInstance()方法
AbstractFactory抽象类：对于getInstance返回的对象加入单例或者非单例的功能，而把真正创建实例对象的createInstance功能留给子类去实现

public T getInstance() {
        T instance;
        if (isSingleton()) {
            if (this.singletonInstance == null) {
                this.singletonInstance = createInstance();
            }
            instance = this.singletonInstance;
        } else {
            instance = createInstance();
        }
        if (instance == null) {
            String msg = "Factory 'createInstance' implementation returned a null object.";
            throw new IllegalStateException(msg);
        }
        return instance;
    }

    protected abstract T createInstance();

IniFactorySupport：加入了Ini ini属性，同过该对象来创建出一个实例，IniFactorySupport对于ini的获取给出了两种方式，方式一：在构造IniFactorySupport时传入Ini 对象，另一种就是加载类路径下默认的Ini，如下：

public static Ini loadDefaultClassPathIni() {
        Ini ini = null;
        if (ResourceUtils.resourceExists(DEFAULT_INI_RESOURCE_PATH)) {
            log.debug("Found shiro.ini at the root of the classpath.");
            ini = new Ini();
            ini.loadFromPath(DEFAULT_INI_RESOURCE_PATH);
            if (CollectionUtils.isEmpty(ini)) {
                log.warn("shiro.ini found at the root of the classpath, but it did not contain any data.");
            }
        }
        return ini;
    }

其中DEFAULT_INI_RESOURCE_PATH为classpath:shiro.ini。然而IniFactorySupport并不负责通过ini配置文件来创建出什么样的对象，它仅仅负责获取ini配置文件，所以它要留出了两个方法让子类实现：

protected abstract T createInstance(Ini ini);

protected abstract T createDefaultInstance();

第一个方法就是通过ini配置文件创建出什么对象，第二个方法就是当获取不到ini配置文件时，要创建默认的对象。
IniSecurityManagerFactory：通过Ini配置文件可以创建出SecurityManager对象，也可以通过ini配置文件创建FilterChainResolver对象，而IniSecurityManagerFactory则是通过ini配置文件来创建SecurityManager的，所以对于泛型的实例化是在该类完成的，如下：

public class IniSecurityManagerFactory extends IniFactorySupport<SecurityManager>
public class IniFilterChainResolverFactory extends IniFactorySupport<FilterChainResolver>

IniSecurityManagerFactory 还不具有web功能，WebIniSecurityManagerFactory则加入了web功能。
可以看到，有很多的类继承关系，每一个类都完成了一个基本功能，把职责划分的更加明确，而不是一锅粥把很多功能放到一个类中，导致很难去复用某些功能。

2 ：将创建的SecurityManager放到SecurityUtils类的静态变量中，供所有对象来访问。

3 ：创建一个Subject实例，接口Subject的文档介绍如下：

A {@code Subject} represents state and security operations for a <em>single</em> application user.These operations include authentication (login/logout), authorization (access control), and session access

及外界通过Subject接口来和SecurityManager进行交互，该接口含有登录、退出、权限判断、获取session,其中的Session可不是平常我们所使用的HttpSession等，而是shiro自定义的，是一个数据上下文，与一个Subject相关联的。
先回到创建Subject的地方：

public static Subject getSubject() {
        Subject subject = ThreadContext.getSubject();
        if (subject == null) {
            subject = (new Subject.Builder()).buildSubject();
            ThreadContext.bind(subject);
        }
        return subject;
    }

一看就是使用的是ThreadLocal设计模式，获取当前线程相关联的Subject 对象，如果没有则创建一个，然后绑定到当前线程。然后我们来看下具体实现：
ThreadContext是org.apache.shiro.util包下的一个工具类，它是用来操作和当前线程绑定的SecurityManager和Subject，它必然包含了一个ThreadLocal对象如下：

public abstract class ThreadContext {

    public static final String SECURITY_MANAGER_KEY = ThreadContext.class.getName() + "_SECURITY_MANAGER_KEY";
    public static final String SUBJECT_KEY = ThreadContext.class.getName() + "_SUBJECT_KEY";

    private static final ThreadLocal<Map<Object, Object>> resources = new InheritableThreadLocalMap<Map<Object, Object>>();

 //略

}

ThreadLocal中所存放的数据是一个Map集合，集合中所存的key有两个SECURITY_MANAGER_KEY 和SUBJECT_KEY ，就是通过这两个key来存取SecurityManager和Subject两个对象的。具体的ThreadLocal设计模式分析可以详见我的另一篇博客http://lgbolgger.iteye.com/blog/2117216。
当前线程还没有绑定一个Subject时，就需要通过Subject.Builder来创建一个然后绑定到当前线程。Builder是Subject的一个内部类，它拥有两个重要的属性，SubjectContext和SecurityManager，创建Builder时使用SecurityUtils工具来获取它的全局静态变量SecurityManager，SubjectContext则是使用newSubjectContextInstance创建一个DefaultSubjectContext对象：

public Builder() {
            this(SecurityUtils.getSecurityManager());
        }

        public Builder(SecurityManager securityManager) {
            if (securityManager == null) {
                throw new NullPointerException("SecurityManager method argument cannot be null.");
            }
            this.securityManager = securityManager;
            this.subjectContext = newSubjectContextInstance();
            if (this.subjectContext == null) {
                throw new IllegalStateException("Subject instance returned from 'newSubjectContextInstance' " +
                        "cannot be null.");
            }
            this.subjectContext.setSecurityManager(securityManager);
        }

protected SubjectContext newSubjectContextInstance() {
            return new DefaultSubjectContext();
        }

Builder准备工作完成后，调用buildSubject来创建一个Subject：

public Subject buildSubject() {
            return this.securityManager.createSubject(this.subjectContext);
        }

最终还是通过securityManager根据subjectContext来创建一个Subject。最终是通过一个SubjectFactory来创建的，SubjectFactory是一个接口，接口方法为Subject createSubject(SubjectContext context)，默认的SubjectFactory实现是DefaultSubjectFactory，DefaultSubjectFactory创建的Subject是DelegatingSubject。至此创建Subject就简单说完了。

4 继续看登陆部分
登陆方法为：void login(AuthenticationToken token)，AuthenticationToken 接口如下：

public interface AuthenticationToken extends Serializable {

    Object getPrincipal();

    Object getCredentials();

}

Principal就相当于用户名，Credentials就相当于密码，AuthenticationToken 的实现UsernamePasswordToken有四个重要属性，即username、char[] password、boolean rememberMe、host。认证过程是由Authenticator来完成的，先来看下Authenticator的整体：

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

很简单，就是根据AuthenticationToken 返回一个AuthenticationInfo ，如果认证失败会抛出AuthenticationException异常。
AbstractAuthenticator实现了Authenticator 接口，它仅仅加入了对认证成功与失败的监听功能，即有一个Collection<AuthenticationListener>集合：

private Collection<AuthenticationListener> listeners;

对于认证过程：

public final AuthenticationInfo authenticate(AuthenticationToken token) throws AuthenticationException {

        if (token == null) {
            throw new IllegalArgumentException("Method argumet (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);
            }
            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 abstract AuthenticationInfo doAuthenticate(AuthenticationToken token)
            throws AuthenticationException;

从上面可以看到实际的认证过程doAuthenticate是交给子类来实现的，AbstractAuthenticator只对认证结果进行处理，认证成功时调用notifySuccess(token, info)通知所有的listener，认证失败时调用notifyFailure(token, ae)通知所有的listener。

具体的认证过程就需要看AbstractAuthenticator子类对于doAuthenticate方法的实现，ModularRealmAuthenticator继承了AbstractAuthenticator，它有两个重要的属性如下

    private Collection<Realm> realms;
    private AuthenticationStrategy authenticationStrategy;

首先就是Realm的概念：就是配置各种角色、权限和用户的地方，即提供了数据源供shiro来使用，它能够根据一个AuthenticationToken中的用户名和密码来判定是否合法等，文档如下：

A <tt>Realm</tt> is a security component that can access application-specific security entities such as users, roles, and permissions to determine authentication and authorization operations

接口如下：

public interface Realm {

    String getName();

    boolean supports(AuthenticationToken token);

    AuthenticationInfo getAuthenticationInfo(AuthenticationToken token) throws AuthenticationException;

}

Realm 首先有一个重要的name属性，全局唯一的标示。supports、getAuthenticationInfo方法就是框架中非常常见的一种写法，ModularRealmAuthenticator拥有Collection<Realm> realms集合，在判定用户合法性时，会首先调用每个Realm的supports方法，如果支持才会去掉用相应的getAuthenticationInfo方法。
关于Realm的详细接口设计之后再给出详细说明，此时先继续回到ModularRealmAuthenticator认证的地方

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);
        }
    }

代码很简单，当只有一个Realm时先调用Realm的supports方法看是否支持，若不支持则抛出认证失败的异常，若支持则调用Realm的getAuthenticationInfo(token)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;
    }

若有多个Realm 时怎样才算是认证成功的呢？这就需要ModularRealmAuthenticator的认证策略AuthenticationStrategy 来指定，对于AuthenticationStrategy目前有三种实现
AllSuccessfulStrategy：即所有的Realm 都验证通过才算是通过
AtLeastOneSuccessfulStrategy：只要有一个Realm 验证通过就算通过
FirstSuccessfulStrategy：这个刚开始不太好理解，和AtLeastOneSuccessfulStrategy稍微有些区别。AtLeastOneSuccessfulStrategy返回了所有Realm认证成功的信息，FirstSuccessfulStrategy只返回了第一个Realm认证成功的信息。
试想一下，如果让你来设计，你会怎么设计？
然后来具体看下AuthenticationStrategy 的接口设计：

public interface AuthenticationStrategy {

    AuthenticationInfo beforeAllAttempts(Collection<? extends Realm> realms, AuthenticationToken token) throws AuthenticationException;

    AuthenticationInfo beforeAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo aggregate) throws AuthenticationException;

    AuthenticationInfo afterAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo singleRealmInfo, AuthenticationInfo aggregateInfo, Throwable t)
            throws AuthenticationException;

    AuthenticationInfo afterAllAttempts(AuthenticationToken token, AuthenticationInfo aggregate) throws AuthenticationException;
}

验证过程是这样的，每一个Realm验证token后都会返回一个当前Realm的验证信息AuthenticationInfo singleRealmInfo，然后呢会有一个贯穿所有Realm验证过程的验证信息AuthenticationInfo aggregateInfo，每一个Realm验证过后会进行singleRealmInfo和aggregateInfo的合并，这是大体的流程

对于AllSuccessfulStrategy来说：它要确保每一个Realm都要验证成功，所以必然
（1）要在beforeAttempt中判断当前realm是否支持token，如不支持抛出异常结束验证过程
（2）要在afterAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo singleRealmInfo, AuthenticationInfo aggregateInfo, Throwable t)中判断是否验证通过了，即异常t为空，并且singleRealmInfo不为空，则表示验证通过了，然后将singleRealmInfo和aggregateInfo合并，所以最终返回的aggregateInfo是几个Realm认证信息合并后的结果
AllSuccessfulStrategy就会在这两处进行把关，一旦不符合抛出异常，认证失败，如下：

public AuthenticationInfo beforeAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo info) throws AuthenticationException {
        if (!realm.supports(token)) {
            String msg = "Realm [" + realm + "] of type [" + realm.getClass().getName() + "] does not support " +
                    " the submitted AuthenticationToken [" + token + "].  The [" + getClass().getName() +
                    "] implementation requires all configured realm(s) to support and be able to process the submitted " +
                    "AuthenticationToken.";
            throw new UnsupportedTokenException(msg);
        }

        return info;
    }

public AuthenticationInfo afterAttempt(Realm realm, AuthenticationToken token, AuthenticationInfo info, AuthenticationInfo aggregate, Throwable t)
            throws AuthenticationException {
        if (t != null) {
            if (t instanceof AuthenticationException) {
                //propagate:
                throw ((AuthenticationException) t);
            } else {
                String msg = "Unable to acquire account data from realm [" + realm + "].  The [" +
                        getClass().getName() + " implementation requires all configured realm(s) to operate successfully " +
                        "for a successful authentication.";
                throw new AuthenticationException(msg, t);
            }
        }
        if (info == null) {
            String msg = "Realm [" + realm + "] could not find any associated account data for the submitted " +
                    "AuthenticationToken [" + token + "].  The [" + getClass().getName() + "] implementation requires " +
                    "all configured realm(s) to acquire valid account data for a submitted token during the " +
                    "log-in process.";
            throw new UnknownAccountException(msg);
        }

        log.debug("Account successfully authenticated using realm [{}]", realm);

        // If non-null account is returned, then the realm was able to authenticate the
        // user - so merge the account with any accumulated before:
        merge(info, aggregate);

        return aggregate;
    }

对于AtLeastOneSuccessfulStrategy来说：它只需确保在所有Realm验证完成之后，判断下aggregateInfo是否含有用户信息即可，若有则表示有些Realm是验证通过了，此时aggregateInfo也是合并后的信息，如下

public AuthenticationInfo afterAllAttempts(AuthenticationToken token, AuthenticationInfo aggregate) throws AuthenticationException {
        //we know if one or more were able to succesfully authenticate if the aggregated account object does not
        //contain null or empty data:
        if (aggregate == null || CollectionUtils.isEmpty(aggregate.getPrincipals())) {
            throw new AuthenticationException("Authentication token of type [" + token.getClass() + "] " +
                    "could not be authenticated by any configured realms.  Please ensure that at least one realm can " +
                    "authenticate these tokens.");
        }

        return aggregate;
    }

对于FirstSuccessfulStrategy来说：它只需要第一个Realm验证成功的信息，不需要去进行合并，所以它必须在合并上做手脚，即不会进行合并，一旦有一个Realm验证成功，信息保存到
aggregateInfo中，之后即使再次验证成功也不会进行合并，如下

protected AuthenticationInfo merge(AuthenticationInfo info, AuthenticationInfo aggregate) {
        if (aggregate != null && !CollectionUtils.isEmpty(aggregate.getPrincipals())) {
            return aggregate;
        }
        return info != null ? info : aggregate;
    }

验证策略分析完成之后，我们来看下ModularRealmAuthenticator的真个验证的代码过程：

protected AuthenticationInfo doMultiRealmAuthentication(Collection<Realm> realms, AuthenticationToken token) {

        AuthenticationStrategy strategy = getAuthenticationStrategy();

        AuthenticationInfo aggregate = strategy.beforeAllAttempts(realms, token);

        if (log.isTraceEnabled()) {
            log.trace("Iterating through {} realms for PAM authentication", realms.size());
        }

        for (Realm realm : realms) {

            aggregate = strategy.beforeAttempt(realm, token, aggregate);

            if (realm.supports(token)) {

                log.trace("Attempting to authenticate token [{}] using realm [{}]", token, realm);

                AuthenticationInfo info = null;
                Throwable t = null;
                try {
                    info = realm.getAuthenticationInfo(token);
                } catch (Throwable throwable) {
                    t = throwable;
                    if (log.isDebugEnabled()) {
                        String msg = "Realm [" + realm + "] threw an exception during a multi-realm authentication attempt:";
                        log.debug(msg, t);
                    }
                }

                aggregate = strategy.afterAttempt(realm, token, info, aggregate, t);

            } else {
                log.debug("Realm [{}] does not support token {}.  Skipping realm.", realm, token);
            }
        }

        aggregate = strategy.afterAllAttempts(token, aggregate);

        return aggregate;
    }

有了之前的分析，这个过程便变的相当容易了。
再回到我们的入门案例中，有了AuthenticationInfo 验证信息，之后进行了那些操作呢？
回到DefaultSecurityManager的如下login方法中：

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;
    }

Subject loggedIn = createSubject(token, info, subject)会根据已有的token、认证结果信息info、和subject从新创建一个已登录的Subject，含有Session信息，创建过程如下：

protected Subject createSubject(AuthenticationToken token, AuthenticationInfo info, Subject existing) {
        SubjectContext context = createSubjectContext();
        context.setAuthenticated(true);
        context.setAuthenticationToken(token);
        context.setAuthenticationInfo(info);
        if (existing != null) {
            context.setSubject(existing);
        }
        return createSubject(context);
    }

就是填充SubjectContext，然后根据SubjectContext来创建Subject，此Subject的信息是经过SubjectDAO保存的，再回到登陆方法：

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;
        }
    }

最后的这些操作就是将刚才创建出来的Subject信息复制到我们所使用的Subject上，即