shiro授权的源码分析

从realm中获取所有需要的用户，角色，权限

从Subject开始，

The term <em>principal</em> is just a fancy security term for any identifying attribute(s) of an application
user, such as a username, or user id, or public key, or anything else you might use in your application to
identify a user.

打开boolean isPermitted(Permission permission)到达DelegatingSubject

public boolean isPermitted(Permission permission) {
        return hasPrincipals() && securityManager.isPermitted(getPrincipals(), permission);
    }

是securityManager在工作

打开isPermitted，到达AuthorizingSecurityManager

public boolean isPermitted(PrincipalCollection principals, Permission permission) {
        return this.authorizer.isPermitted(principals, permission);
    }

此处是插曲，插曲开始=========================================================

AuthorizingSecurityManager是什么？

Shiro support of a {@link SecurityManager} class hierarchy that delegates all
authorization (access control) operations to a wrapped {@link Authorizer Authorizer} instance. That is,
this class implements all the <tt>Authorizer</tt> methods in the {@link SecurityManager SecurityManager}
interface, but in reality, those methods are merely passthrough calls to the underlying 'real'
<tt>Authorizer</tt> instance.

先要找authorizer：

public abstract class AuthorizingSecurityManager extends AuthenticatingSecurityManager {

    /**
     * The wrapped instance to which all of this <tt>SecurityManager</tt> authorization calls are delegated.
     */
    private Authorizer authorizer;

    /**
     * Default no-arg constructor that initializes an internal default
     * {@link org.apache.shiro.authz.ModularRealmAuthorizer ModularRealmAuthorizer}.
     */
    public AuthorizingSecurityManager() {
        super();
        this.authorizer = new ModularRealmAuthorizer();
    }

    /**
     * Returns the underlying wrapped <tt>Authorizer</tt> instance to which this <tt>SecurityManager</tt>
     * implementation delegates all of its authorization calls.
     *
     * @return the wrapped <tt>Authorizer</tt> used by this <tt>SecurityManager</tt> implementation.
     */
    public Authorizer getAuthorizer() {
        return authorizer;
    }

    /**
     * Sets the underlying <tt>Authorizer</tt> instance to which this <tt>SecurityManager</tt> implementation will
     * delegate all of its authorization calls.
     *
     * @param authorizer the <tt>Authorizer</tt> this <tt>SecurityManager</tt> should wrap and delegate all of its
     *                   authorization calls to.
     */
    public void setAuthorizer(Authorizer authorizer) {
        if (authorizer == null) {
            String msg = "Authorizer argument cannot be null.";
            throw new IllegalArgumentException(msg);
        }
        this.authorizer = authorizer;
    }

找到了,原来AuthorizingSecurityManager中的authorizer是new ModularRealmAuthorizer()

插曲结束=========================================================

打开this.authorizer.isPermitted(principals, permission)

看到：

知道authorizer是new ModularRealmAuthorizer(),所以点开ModularRealmAuthorizer看到:

public boolean isPermitted(PrincipalCollection principals, Permission permission) {
        assertRealmsConfigured();
        for (Realm realm : getRealms()) {
            if (!(realm instanceof Authorizer)) continue;
            if (((Authorizer) realm).isPermitted(principals, permission)) {
                return true;
            }
        }
        return false;
    }

这里出现了Realm

打开getRealms()到达了ModularRealmAuthorizer，神奇：

public ModularRealmAuthorizer(Collection<Realm> realms) {
        setRealms(realms);
    }

看到在ModularRealmAuthorizer的构造器中注入了realm，

原来AuthorizingSecurityManager在初始化的时候，已经把realm注入到属性authorizer中了就是ModularRealmAuthorizer中了

接下来打开(Authorizer) realm).isPermitted(principals, permission)

 应该选择AuthorizingRealm，打开：

public boolean isPermitted(PrincipalCollection principals, Permission permission) {
        AuthorizationInfo info = getAuthorizationInfo(principals);
        return isPermitted(permission, info);
    }

打开getAuthorizationInfo(principals)

protected AuthorizationInfo getAuthorizationInfo(PrincipalCollection principals) {

        if (principals == null) {
            return null;
        }

        AuthorizationInfo info = null;

        if (log.isTraceEnabled()) {
            log.trace("Retrieving AuthorizationInfo for principals [" + principals + "]");
        }

        Cache<Object, AuthorizationInfo> cache = getAvailableAuthorizationCache();
        if (cache != null) {
            if (log.isTraceEnabled()) {
                log.trace("Attempting to retrieve the AuthorizationInfo from cache.");
            }
            Object key = getAuthorizationCacheKey(principals);
            info = cache.get(key);
            if (log.isTraceEnabled()) {
                if (info == null) {
                    log.trace("No AuthorizationInfo found in cache for principals [" + principals + "]");
                } else {
                    log.trace("AuthorizationInfo found in cache for principals [" + principals + "]");
                }
            }
        }


        if (info == null) {
            // Call template method if the info was not found in a cache
            info = doGetAuthorizationInfo(principals);
            // If the info is not null and the cache has been created, then cache the authorization info.
            if (info != null && cache != null) {
                if (log.isTraceEnabled()) {
                    log.trace("Caching authorization info for principals: [" + principals + "].");
                }
                Object key = getAuthorizationCacheKey(principals);
                cache.put(key, info);
            }
        }

        return info;
    }

首次登录，缓存是空的，所以应该看info==null的部分，打开doGetAuthorizationInfo(principals)

走到头了，到这授权就走到头了

看到它是AuthenticatingRealm的子类，所以具有父类的所有方法，

所以授权是用的这个类的方法doGetAuthorizationInfo(PrincipalCollection principals)

所以继承这个类，重写这个方法就可以自定义自己的授权了

AuthorizingSecurityManager的继承关系：

有这些方法：