Shiro的AOP横切模式-注解权限控制

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.spring.security.interceptor;

import org.apache.shiro.authz.annotation.*;
import org.apache.shiro.mgt.SecurityManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.support.StaticMethodMatcherPointcutAdvisor;
import org.springframework.core.annotation.AnnotationUtils;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;


/**
 * TODO - complete JavaDoc
 *
 * @since 0.1
 */
@SuppressWarnings({"unchecked"})
public class AuthorizationAttributeSourceAdvisor extends StaticMethodMatcherPointcutAdvisor {

    private static final Logger log = LoggerFactory.getLogger(AuthorizationAttributeSourceAdvisor.class);

    // 权限控制支持的注解
    private static final Class<? extends Annotation>[] AUTHZ_ANNOTATION_CLASSES =
            new Class[] {
                    RequiresPermissions.class, RequiresRoles.class,
                    RequiresUser.class, RequiresGuest.class, RequiresAuthentication.class
            };

    protected SecurityManager securityManager = null;

    /**
     * Create a new AuthorizationAttributeSourceAdvisor.
     *
     * 构造方法创建方法拦截器并设置为通知
     */
    public AuthorizationAttributeSourceAdvisor() {
        setAdvice(new AopAllianceAnnotationsAuthorizingMethodInterceptor());
    }

    public SecurityManager getSecurityManager() {
        return securityManager;
    }

    public void setSecurityManager(org.apache.shiro.mgt.SecurityManager securityManager) {
        this.securityManager = securityManager;
    }

    /**
     * Returns <tt>true</tt> if the method or the class has any Shiro annotations, false otherwise.
     * The annotations inspected are:
     * <ul>
     * <li>{@link org.apache.shiro.authz.annotation.RequiresAuthentication RequiresAuthentication}</li>
     * <li>{@link org.apache.shiro.authz.annotation.RequiresUser RequiresUser}</li>
     * <li>{@link org.apache.shiro.authz.annotation.RequiresGuest RequiresGuest}</li>
     * <li>{@link org.apache.shiro.authz.annotation.RequiresRoles RequiresRoles}</li>
     * <li>{@link org.apache.shiro.authz.annotation.RequiresPermissions RequiresPermissions}</li>
     * </ul>
     *
     * @param method      the method to check for a Shiro annotation
     * @param targetClass the class potentially declaring Shiro annotations
     * @return <tt>true</tt> if the method has a Shiro annotation, false otherwise.
     * @see org.springframework.aop.MethodMatcher#matches(java.lang.reflect.Method, Class)
     *
     *
     * 切入点方法匹配方式
     */
    public boolean matches(Method method, Class targetClass) {
        Method m = method;

        if ( isAuthzAnnotationPresent(m) ) {
            return true;
        }

        //The ‘method‘ parameter could be from an interface that doesn‘t have the annotation.
        //Check to see if the implementation has it.
        if ( targetClass != null) {
            try {
                m = targetClass.getMethod(m.getName(), m.getParameterTypes());
                return isAuthzAnnotationPresent(m) || isAuthzAnnotationPresent(targetClass);
            } catch (NoSuchMethodException ignored) {
                //default return value is false.  If we can‘t find the method, then obviously
                //there is no annotation, so just use the default return value.
            }
        }

        return false;
    }

    // 判断目标方法上是否有注解
    private boolean isAuthzAnnotationPresent(Class<?> targetClazz) {
        for( Class<? extends Annotation> annClass : AUTHZ_ANNOTATION_CLASSES ) {
            Annotation a = AnnotationUtils.findAnnotation(targetClazz, annClass);
            if ( a != null ) {
                return true;
            }
        }
        return false;
    }

    // 判断目标方法上是否有注解
    private boolean isAuthzAnnotationPresent(Method method) {
        for( Class<? extends Annotation> annClass : AUTHZ_ANNOTATION_CLASSES ) {
            Annotation a = AnnotationUtils.findAnnotation(method, annClass);
            if ( a != null ) {
                return true;
            }
        }
        return false;
    }

}

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.spring.security.interceptor;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.shiro.aop.AnnotationResolver;
import org.apache.shiro.authz.aop.*;
import org.apache.shiro.spring.aop.SpringAnnotationResolver;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

/**
 * Allows Shiro Annotations to work in any <a href="http://aopalliance.sourceforge.net/">AOP Alliance</a>
 * specific implementation environment (for example, Spring).
 *
 * @since 0.2
 */
public class AopAllianceAnnotationsAuthorizingMethodInterceptor
        extends AnnotationsAuthorizingMethodInterceptor implements MethodInterceptor {

    // 构造方法内创建AnnotationResolver注解解析器（主要是判断方法上是否有注解）
    // 创建AnnotationMethodInterceptor注解方法拦截器    
    public AopAllianceAnnotationsAuthorizingMethodInterceptor() {
        List<AuthorizingAnnotationMethodInterceptor> interceptors =
                new ArrayList<AuthorizingAnnotationMethodInterceptor>(5);

        //use a Spring-specific Annotation resolver - Spring‘s AnnotationUtils is nicer than the
        //raw JDK resolution process.
        AnnotationResolver resolver = new SpringAnnotationResolver();
        //we can re-use the same resolver instance - it does not retain state:
        interceptors.add(new RoleAnnotationMethodInterceptor(resolver));
        interceptors.add(new PermissionAnnotationMethodInterceptor(resolver));
        interceptors.add(new AuthenticatedAnnotationMethodInterceptor(resolver));
        interceptors.add(new UserAnnotationMethodInterceptor(resolver));
        interceptors.add(new GuestAnnotationMethodInterceptor(resolver));

　　　　　// 为子类AnnotationsAuthorizingMethodInterceptor注入方法拦截器
        setMethodInterceptors(interceptors);
    }
    /**
     * Creates a {@link MethodInvocation MethodInvocation} that wraps an
     * {@link org.aopalliance.intercept.MethodInvocation org.aopalliance.intercept.MethodInvocation} instance,
     * enabling Shiro Annotations in <a href="http://aopalliance.sourceforge.net/">AOP Alliance</a> environments
     * (Spring, etc).
     *
     * @param implSpecificMethodInvocation AOP Alliance {@link org.aopalliance.intercept.MethodInvocation MethodInvocation}
     * @return a Shiro {@link MethodInvocation MethodInvocation} instance that wraps the AOP Alliance instance.
     *
     * 将org.aopalliance.intercept.MethodInvocation包装成org.apache.shiro.aop.MethodInvocation
     */
    protected org.apache.shiro.aop.MethodInvocation createMethodInvocation(Object implSpecificMethodInvocation) {
        final MethodInvocation mi = (MethodInvocation) implSpecificMethodInvocation;

        return new org.apache.shiro.aop.MethodInvocation() {
            public Method getMethod() {
                return mi.getMethod();
            }

            public Object[] getArguments() {
                return mi.getArguments();
            }

            public String toString() {
                return "Method invocation [" + mi.getMethod() + "]";
            }

            public Object proceed() throws Throwable {
                return mi.proceed();
            }

            public Object getThis() {
                return mi.getThis();
            }
        };
    }

    /**
     * Simply casts the method argument to an
     * {@link org.aopalliance.intercept.MethodInvocation org.aopalliance.intercept.MethodInvocation} and then
     * calls <code>methodInvocation.{@link org.aopalliance.intercept.MethodInvocation#proceed proceed}()</code>
     *
     * @param aopAllianceMethodInvocation the {@link org.aopalliance.intercept.MethodInvocation org.aopalliance.intercept.MethodInvocation}
     * @return the {@link org.aopalliance.intercept.MethodInvocation#proceed() org.aopalliance.intercept.MethodInvocation.proceed()} method call result.
     * @throws Throwable if the underlying AOP Alliance <code>proceed()</code> call throws a <code>Throwable</code>.
     */
    protected Object continueInvocation(Object aopAllianceMethodInvocation) throws Throwable {
        MethodInvocation mi = (MethodInvocation) aopAllianceMethodInvocation;
        return mi.proceed();
    }

    /**
     * Creates a Shiro {@link MethodInvocation MethodInvocation} instance and then immediately calls
     * {@link org.apache.shiro.authz.aop.AuthorizingMethodInterceptor#invoke super.invoke}.
     *
     * @param methodInvocation the AOP Alliance-specific <code>methodInvocation</code> instance.
     * @return the return value from invoking the method invocation.
     * @throws Throwable if the underlying AOP Alliance method invocation throws a <code>Throwable</code>.
     *
     * 对MethodInvocation进行包装之后调用父类的invoke方法
     */
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        org.apache.shiro.aop.MethodInvocation mi = createMethodInvocation(methodInvocation);
        return super.invoke(mi);
    }
}

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.authz.aop;

import org.apache.shiro.aop.MethodInterceptorSupport;
import org.apache.shiro.aop.MethodInvocation;
import org.apache.shiro.authz.AuthorizationException;

/**
 * Basic abstract class to support intercepting methods that perform authorization (access control) checks.
 *
 * @since 0.9
 */
public abstract class AuthorizingMethodInterceptor extends MethodInterceptorSupport {

    /**
     * Invokes the specified method (<code>methodInvocation.{@link org.apache.shiro.aop.MethodInvocation#proceed proceed}()</code>
     * if authorization is allowed by first
     * calling {@link #assertAuthorized(org.apache.shiro.aop.MethodInvocation) assertAuthorized}.
     */
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        assertAuthorized(methodInvocation);
        return methodInvocation.proceed();
    }

    /**
     * Asserts that the specified MethodInvocation is allowed to continue by performing any necessary authorization
     * (access control) checks first.
     * @param methodInvocation the <code>MethodInvocation</code> to invoke.
     * @throws AuthorizationException if the <code>methodInvocation</code> should not be allowed to continue/execute.
     *
     * 判断是否有权限的事交给具体的子类（AnnotationsAuthorizingMethodInterceptor）去处理
     */
    protected abstract void assertAuthorized(MethodInvocation methodInvocation) throws AuthorizationException;

}

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.authz.aop;

import java.util.ArrayList;
import java.util.Collection;

import org.apache.shiro.aop.MethodInvocation;
import org.apache.shiro.authz.AuthorizationException;

/**
 * An <tt>AnnotationsAuthorizingMethodInterceptor</tt> is a MethodInterceptor that asserts a given method is authorized
 * to execute based on one or more configured <tt>AuthorizingAnnotationMethodInterceptor</tt>s.
 *
 * <p>This allows multiple annotations on a method to be processed before the method
 * executes, and if any of the <tt>AuthorizingAnnotationMethodInterceptor</tt>s indicate that the method should not be
 * executed, an <tt>AuthorizationException</tt> will be thrown, otherwise the method will be invoked as expected.
 *
 * <p>It is essentially a convenience mechanism to allow multiple annotations to be processed in a single method
 * interceptor.
 *
 * @since 0.2
 */
public abstract class AnnotationsAuthorizingMethodInterceptor extends AuthorizingMethodInterceptor {

    /**
     * The method interceptors to execute for the annotated method.
     */
    protected Collection<AuthorizingAnnotationMethodInterceptor> methodInterceptors;

    /**
     * Default no-argument constructor that defaults the 
     * {@link #methodInterceptors methodInterceptors} attribute to contain two interceptors by default - the
     * {@link RoleAnnotationMethodInterceptor RoleAnnotationMethodInterceptor} and the
     * {@link PermissionAnnotationMethodInterceptor PermissionAnnotationMethodInterceptor} to
     * support role and permission annotations.
     *
     * 构造时默认创建5个权限注解方法拦截器
     * 但是又提供了setMethodInterceptors(Collection<AuthorizingAnnotationMethodInterceptor> methodInterceptors)注入更扩展的权限注解方法拦截器
     */
    public AnnotationsAuthorizingMethodInterceptor() {
        methodInterceptors = new ArrayList<AuthorizingAnnotationMethodInterceptor>(5);
        methodInterceptors.add(new RoleAnnotationMethodInterceptor());
        methodInterceptors.add(new PermissionAnnotationMethodInterceptor());
        methodInterceptors.add(new AuthenticatedAnnotationMethodInterceptor());
        methodInterceptors.add(new UserAnnotationMethodInterceptor());
        methodInterceptors.add(new GuestAnnotationMethodInterceptor());
    }

    /**
     * Returns the method interceptors to execute for the annotated method.
     * <p/>
     * Unless overridden by the {@link #setMethodInterceptors(java.util.Collection)} method, the default collection
     * contains a
     * {@link RoleAnnotationMethodInterceptor RoleAnnotationMethodInterceptor} and a
     * {@link PermissionAnnotationMethodInterceptor PermissionAnnotationMethodInterceptor} to
     * support role and permission annotations automatically.
     * @return the method interceptors to execute for the annotated method.
     */
    public Collection<AuthorizingAnnotationMethodInterceptor> getMethodInterceptors() {
        return methodInterceptors;
    }

    /**
     * Sets the method interceptors to execute for the annotated method.
     * @param methodInterceptors the method interceptors to execute for the annotated method.
     * @see #getMethodInterceptors()
     *
     * 可注入具有扩展性的权限注解方法拦截器
     * 子类AopAllianceAnnotationsAuthorizingMethodInterceptor构造时调用了该方法
     */
    public void setMethodInterceptors(Collection<AuthorizingAnnotationMethodInterceptor> methodInterceptors) {
        this.methodInterceptors = methodInterceptors;
    }

    /**
     * Iterates over the internal {@link #getMethodInterceptors() methodInterceptors} collection, and for each one,
     * ensures that if the interceptor
     * {@link AuthorizingAnnotationMethodInterceptor#supports(org.apache.shiro.aop.MethodInvocation) supports}
     * the invocation, that the interceptor
     * {@link AuthorizingAnnotationMethodInterceptor#assertAuthorized(org.apache.shiro.aop.MethodInvocation) asserts}
     * that the invocation is authorized to proceed.
     *
     * 遍历各个权限注解方法拦截器如new RoleAnnotationMethodInterceptor(new SpringAnnotationResolver())
     * 此时是注解权限方法拦截器内使用权限注解方法拦截器判断是否有权限，具体的判断要权限注解方法拦截器来处理
     */
    protected void assertAuthorized(MethodInvocation methodInvocation) throws AuthorizationException {
        //default implementation just ensures no deny votes are cast:
        Collection<AuthorizingAnnotationMethodInterceptor> aamis = getMethodInterceptors();
        if (aamis != null && !aamis.isEmpty()) {
            for (AuthorizingAnnotationMethodInterceptor aami : aamis) {
                if (aami.supports(methodInvocation)) {
                    aami.assertAuthorized(methodInvocation);
                }
            }
        }
    }
}

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.aop;

import java.lang.annotation.Annotation;

/**
 * MethodInterceptor that inspects a specific annotation on the method invocation before continuing
 * its execution.
 * </p>
 * The annotation is acquired from the {@link MethodInvocation MethodInvocation} via a
 * {@link AnnotationResolver AnnotationResolver} instance that may be configured.  Unless
 * overridden, the default {@code AnnotationResolver} is a
 *
 * @since 0.9
 */
public abstract class AnnotationMethodInterceptor extends MethodInterceptorSupport {

    private AnnotationHandler handler;

    /**
     * The resolver to use to find annotations on intercepted methods.
     *
     * @since 1.1
     */
    private AnnotationResolver resolver;

    /**
     * Constructs an <code>AnnotationMethodInterceptor</code> with the
     * {@link AnnotationHandler AnnotationHandler} that will be used to process annotations of a
     * corresponding type.
     *
     * @param handler the handler to delegate to for processing the annotation.
     *
     * 构造时注入注解处理器和默认的注解解析器
     */
    public AnnotationMethodInterceptor(AnnotationHandler handler) {
        this(handler, new DefaultAnnotationResolver());
    }

    /**
     * Constructs an <code>AnnotationMethodInterceptor</code> with the
     * {@link AnnotationHandler AnnotationHandler} that will be used to process annotations of a
     * corresponding type, using the specified {@code AnnotationResolver} to acquire annotations
     * at runtime.
     *
     * @param handler  the handler to use to process any discovered annotation
     * @param resolver the resolver to use to locate/acquire the annotation
     * @since 1.1
     */
    public AnnotationMethodInterceptor(AnnotationHandler handler, AnnotationResolver resolver) {
        if (handler == null) {
            throw new IllegalArgumentException("AnnotationHandler argument cannot be null.");
        }
        setHandler(handler);
        setResolver(resolver != null ? resolver : new DefaultAnnotationResolver());
    }

    /**
     * Returns the {@code AnnotationHandler} used to perform authorization behavior based on
     * an annotation discovered at runtime.
     *
     * @return the {@code AnnotationHandler} used to perform authorization behavior based on
     *         an annotation discovered at runtime.
     */
    public AnnotationHandler getHandler() {
        return handler;
    }

    /**
     * Sets the {@code AnnotationHandler} used to perform authorization behavior based on
     * an annotation discovered at runtime.
     *
     * @param handler the {@code AnnotationHandler} used to perform authorization behavior based on
     *                an annotation discovered at runtime.
     *
     * 支持扩展的注解处理器
     */
    public void setHandler(AnnotationHandler handler) {
        this.handler = handler;
    }

    /**
     * Returns the {@code AnnotationResolver} to use to acquire annotations from intercepted
     * methods at runtime.  The annotation is then used by the {@link #getHandler handler} to
     * perform authorization logic.
     *
     * @return the {@code AnnotationResolver} to use to acquire annotations from intercepted
     *         methods at runtime.
     * @since 1.1
     */
    public AnnotationResolver getResolver() {
        return resolver;
    }

    /**
     * Returns the {@code AnnotationResolver} to use to acquire annotations from intercepted
     * methods at runtime.  The annotation is then used by the {@link #getHandler handler} to
     * perform authorization logic.
     *
     * @param resolver the {@code AnnotationResolver} to use to acquire annotations from intercepted
     *                 methods at runtime.
     * @since 1.1
     *
     * 支持扩展的注解解析器
     */
    public void setResolver(AnnotationResolver resolver) {
        this.resolver = resolver;
    }

    /**
     * Returns <code>true</code> if this interceptor supports, that is, should inspect, the specified
     * <code>MethodInvocation</code>, <code>false</code> otherwise.
     * <p/>
     * The default implementation simply does the following:
     * <p/>
     * <code>return {@link #getAnnotation(MethodInvocation) getAnnotation(mi)} != null</code>
     *
     * @param mi the <code>MethodInvocation</code> for the method being invoked.
     * @return <code>true</code> if this interceptor supports, that is, should inspect, the specified
     *         <code>MethodInvocation</code>, <code>false</code> otherwise.
     *
     * 判断目标方法上是否有权限注解
     */
    public boolean supports(MethodInvocation mi) {
        return getAnnotation(mi) != null;
    }

    /**
     * Returns the Annotation that this interceptor will process for the specified method invocation.
     * <p/>
     * The default implementation acquires the annotation using an annotation
     * {@link #getResolver resolver} using the internal annotation {@link #getHandler handler}‘s
     * {@link org.apache.shiro.aop.AnnotationHandler#getAnnotationClass() annotationClass}.
     *
     * @param mi the MethodInvocation wrapping the Method from which the Annotation will be acquired.
     * @return the Annotation that this interceptor will process for the specified method invocation.
     *
     * 使用注解解析器获得目标方法上的注解
     */
    protected Annotation getAnnotation(MethodInvocation mi) {
        return getResolver().getAnnotation(mi, getHandler().getAnnotationClass());
    }
}

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.shiro.authz.aop;

import org.apache.shiro.aop.AnnotationMethodInterceptor;
import org.apache.shiro.aop.AnnotationResolver;
import org.apache.shiro.aop.MethodInvocation;
import org.apache.shiro.authz.AuthorizationException;


/**
 * An <tt>AnnotationMethodInterceptor</tt> that asserts the calling code is authorized to execute the method
 * before allowing the invocation to continue by inspecting code annotations to perform an access control check.
 *
 * @since 0.1
 */
public abstract class AuthorizingAnnotationMethodInterceptor extends AnnotationMethodInterceptor
{
    
    /**
     * Constructor that ensures the internal <code>handler</code> is set which will be used to perform the
     * authorization assertion checks when a supported annotation is encountered.
     * @param handler the internal <code>handler</code> used to perform authorization assertion checks when a 
     * supported annotation is encountered.
     */
    public AuthorizingAnnotationMethodInterceptor( AuthorizingAnnotationHandler handler ) {
        super(handler);
    }

    /**
     *
     * @param handler
     * @param resolver
     * @since 1.1
     *
     * 将注入进来的handler和resolver提供给父类AnnotationMethodInterceptor
     */
    public AuthorizingAnnotationMethodInterceptor( AuthorizingAnnotationHandler handler,
                                                   AnnotationResolver resolver) {
        super(handler, resolver);
    }

    /**
     * Ensures the <code>methodInvocation</code> is allowed to execute first before proceeding by calling the
     * {@link #assertAuthorized(org.apache.shiro.aop.MethodInvocation) assertAuthorized} method first.
     *
     * @param methodInvocation the method invocation to check for authorization prior to allowing it to proceed/execute.
     * @return the return value from the method invocation (the value of {@link org.apache.shiro.aop.MethodInvocation#proceed() MethodInvocation.proceed()}).
     * @throws org.apache.shiro.authz.AuthorizationException if the <code>MethodInvocation</code> is not allowed to proceed.
     * @throws Throwable if any other error occurs.
     */
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        assertAuthorized(methodInvocation);
        return methodInvocation.proceed();
    }

    /**
     * Ensures the calling Subject is authorized to execute the specified <code>MethodInvocation</code>.
     * <p/>
     * As this is an AnnotationMethodInterceptor, this implementation merely delegates to the internal
     * {@link AuthorizingAnnotationHandler AuthorizingAnnotationHandler} by first acquiring the annotation by
     * calling {@link #getAnnotation(MethodInvocation) getAnnotation(methodInvocation)} and then calls
     * {@link AuthorizingAnnotationHandler#assertAuthorized(java.lang.annotation.Annotation) handler.assertAuthorized(annotation)}.
     *
     * @param mi the <code>MethodInvocation</code> to check to see if it is allowed to proceed/execute.
     * @throws AuthorizationException if the method invocation is not allowed to continue/execute.
     *
     * 使用权限注解处理器来处理判断是否具备权限
     */
    public void assertAuthorized(MethodInvocation mi) throws AuthorizationException {
        try {
            ((AuthorizingAnnotationHandler)getHandler()).assertAuthorized(getAnnotation(mi));
        }
        catch(AuthorizationException ae) {
            // Annotation handler doesn‘t know why it was called, so add the information here if possible. 
            // Don‘t wrap the exception here since we don‘t want to mask the specific exception, such as 
            // UnauthenticatedException etc. 
            if (ae.getCause() == null) ae.initCause(new AuthorizationException("Not authorized to invoke method: " + mi.getMethod()));
            throw ae;
        }         
    }
}