ShiroFilterFactoryBean源码及阻截原理深入分析
ShiroFilterFactoryBean源码及阻截原理深入分析
HelloRookie 发表于1年前
ShiroFilterFactoryBean源码及阻截原理深入分析
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ShiroFilterFactoryBean源码及拦截原理深入分析

本篇文章篇幅比较长,但是细看下去相信对学习Shiro应该会有帮助。好了,闲话不多说,直接进入正题:

Shiro提供了与Web集成的支持,其通过一个ShiroFilter入口来拦截需要安全控制的URL,然后进行相应的控制,ShiroFilter类似于如Strut2/SpringMVC这种web框架的前端控制器,其是安全控制的入口点,其负责读取配置(如ini配置文件),然后判断URL是否需要登录/权限等工作。

而要在Spring中使用Shiro的话,可在web.xml中配置一个DelegatingFilterProxyDelegatingFilterProxy作用是自动到Spring容器查找名字为shiroFilterfilter-name)的bean并把所有Filter的操作委托给它。

首先是在web.xml中配置DelegatingFilterProxy

<filter>
    <filter-name>shiroFilter</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    <init-param>
        <param-name>targetFilterLifecycle</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>shiroFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

配置好DelegatingFilterProxy后,下面只要再把ShiroFilter配置到Spring容器(此处为Spring的配置文件)即可:

<bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean">
    <property name="securityManager" ref="securityManager"/>
</bean>

可以看到我们使用了ShiroFilterFactoryBean来创建shiroFilter,这里用到了Spring中一种特殊的Bean——FactoryBean。当需要得到名为”shiroFilter“的bean时,会调用其getObject()来获取实例。下面我们通过分析ShiroFilterFactoryBean创建实例的过程来探究Shiro是如何实现安全拦截的:

    public Object getObject() throws Exception {
        if (instance == null) {
            instance = createInstance();
        }
        return instance;
    }

其中调用了createInstance()来创建实例:

  protected AbstractShiroFilter createInstance() throws Exception {

        // 这里是通过FactoryBean注入的SecurityManager(必须)
        SecurityManager securityManager = getSecurityManager();
        if (securityManager == null) {
            String msg = "SecurityManager property must be set.";
            throw new BeanInitializationException(msg);
        }

        if (!(securityManager instanceof WebSecurityManager)) {
            String msg = "The security manager does not implement the WebSecurityManager interface.";
            throw new BeanInitializationException(msg);
        }

        FilterChainManager manager = createFilterChainManager();

        PathMatchingFilterChainResolver chainResolver = new PathMatchingFilterChainResolver();
        chainResolver.setFilterChainManager(manager);

        return new SpringShiroFilter((WebSecurityManager) securityManager, chainResolver);
    }

可以看到创建SpringShiroFilter时用到了两个组件:SecurityManagerChainResolver

  • SecurityManager:我们知道其在Shiro中的地位,类似于一个“安全大管家”,相当于SpringMVC中的DispatcherServlet或者Struts2中的FilterDispatcher,是Shiro的心脏,所有具体的交互都通过SecurityManager进行控制,它管理着所有Subject、且负责进行认证和授权、及会话、缓存的管理。
  • ChainResolver:Filter链解析器,用来解析出该次请求需要执行的Filter链。
  • PathMatchingFilterChainResolverChainResolver的实现类,其中还包含了两个重要组件FilterChainManagerPatternMatcher
  • FilterChainManager:管理着Filter和Filter链,配合PathMatchingFilterChainResolver解析出Filter链
  • PatternMatcher:用来进行请求路径匹配,默认为Ant风格的路径匹配

先有一个大体的了解,那么对于源码分析会有不少帮助。下面会对以上两个重要的组件进行分析,包括PathMatchingFilterChainResolverFilterChainManager。首先贴一段ShiroFilter的在配置文件中的定义:

<!-- Shiro的Web过滤器 -->
    <bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean">
        <property name="securityManager" ref="securityManager" />
        <property name="loginUrl" value="/login" />
        <property name="unauthorizedUrl" value="/special/unauthorized" />
        <property name="filters">
            <util:map>
                <entry key="authc" value-ref="formAuthenticationFilter" />
                <entry key="logout" value-ref="logoutFilter" />
                <entry key="ssl" value-ref="sslFilter"></entry>
            </util:map>
        </property>
        <property name="filterChainDefinitions">
            <value>
                /resources/** = anon
                /plugin/** = anon
                /download/** = anon
                /special/unauthorized = anon
                /register = anon
                /login = ssl,authc
                /logout = logout
                /admin/** = roles[admin]

                /** = user
            </value>
        </property>
    </bean>

再来看看PathMatchingFilterChainResolverFilterChainManager的创建过程:

  protected FilterChainManager createFilterChainManager() {

        // 默认使用的FilterChainManager是DefaultFilterChainManager
        DefaultFilterChainManager manager = new DefaultFilterChainManager();
        // DefaultFilterChainManager默认会注册的filters(后面会列出)
        Map<String, Filter> defaultFilters = manager.getFilters();

        // 将ShiroFilterFactoryBean配置的一些公共属性(上面配置的loginUrl,successUrl,unauthorizeUrl)应用到默认注册的filter上去
        for (Filter filter : defaultFilters.values()) {
            applyGlobalPropertiesIfNecessary(filter);
        }

        // 处理自定义的filter(上面配置的filters属性),步骤类似上面
        Map<String, Filter> filters = getFilters();
        if (!CollectionUtils.isEmpty(filters)) {
            for (Map.Entry<String, Filter> entry : filters.entrySet()) {
                String name = entry.getKey();
                Filter filter = entry.getValue();
                applyGlobalPropertiesIfNecessary(filter);
                if (filter instanceof Nameable) {
                    ((Nameable) filter).setName(name);
                }
                // 将Filter添加到manager中去,可以看到对于Filter的管理是依赖于FilterChainManager的
                manager.addFilter(name, filter, false);
            }
        }

        // 根据FilterChainDefinition的配置来构建Filter链(上面配置的filterChainDefinitions属性)
        Map<String, String> chains = getFilterChainDefinitionMap();
        if (!CollectionUtils.isEmpty(chains)) {
            for (Map.Entry<String, String> entry : chains.entrySet()) {
                String url = entry.getKey();
                String chainDefinition = entry.getValue();
                // 后面会分析该步的源码,功能上就是创建Filter链
                manager.createChain(url, chainDefinition);
            }
        }

        return manager;
    }

下面有必要来看看DefaultFilterChainManager的源码,分析一下上面调用到的方法。先来看看他的几个重要的属性:

    private FilterConfig filterConfig;

    private Map<String, Filter> filters; //pool of filters available for creating chains

    private Map<String, NamedFilterList> filterChains; //key: chain name, value: chain

其中filterConfig仅在初始化Filter时有效,而我们自定义的Filter都不是init的,所以该属性可以暂时忽略()。 
而后面两张map就重要了:filters中缓存了所有添加的filter,filterChains则缓存了所有的filterChain。其中前者的key是filter name,value是Filter。而后者的key是chain name,value是NamedFilterList。 
有的童鞋可能会问NamedFilterList是怎么样的结构呢,你可以把它当成List<Filter>,这样就好理解了吧。下面再分析刚才createFilterChainManager()中调用过的manager的几个方法:

  • addFilter(缓存filter让manager来管理)
    public void addFilter(String name, Filter filter, boolean init) {
        addFilter(name, filter, init, true);
    }

    protected void addFilter(String name, Filter filter, boolean init, boolean overwrite) {
        Filter existing = getFilter(name);
        if (existing == null || overwrite) {
            if (filter instanceof Nameable) {
                ((Nameable) filter).setName(name);
            }
            if (init) {
                initFilter(filter);
            }
            this.filters.put(name, filter);
        }
    }

filter缓存到filters这张map里,不管是默认注册的还是自定义的都需要FilterChainManager来统一管理。

  • createChain:创建filterChain并将定义的filter都加进去
    // chainName就是拦截路径"/resources/**",chainDefinition就是多个过滤器名的字符串
    public void createChain(String chainName, String chainDefinition) {
        if (!StringUtils.hasText(chainName)) {
            throw new NullPointerException("chainName cannot be null or empty.");
        }
        if (!StringUtils.hasText(chainDefinition)) {
            throw new NullPointerException("chainDefinition cannot be null or empty.");
        }

        if (log.isDebugEnabled()) {
            log.debug("Creating chain [" + chainName + "] from String definition [" + chainDefinition + "]");
        }

        // 先分离出配置的各个filter,比如 
        // "authc, roles[admin,user], perms[file:edit]" 分离后的结果是:
        // { "authc", "roles[admin,user]", "perms[file:edit]" }
        String[] filterTokens = splitChainDefinition(chainDefinition);

        // 进一步分离出"[]"内的内容,其中nameConfigPair是一个长度为2的数组
        // 比如 roles[admin,user] 经过解析后的nameConfigPair 为{"roles", "admin,user"}
        for (String token : filterTokens) {
            String[] nameConfigPair = toNameConfigPair(token);

            // 得到了 拦截路径、filter以及可能的"[]"中的值,那么执行addToChain
            addToChain(chainName, nameConfigPair[0], nameConfigPair[1]);
        }
    }
  • addToChain
   public void addToChain(String chainName, String filterName, String chainSpecificFilterConfig) {
        if (!StringUtils.hasText(chainName)) {
            throw new IllegalArgumentException("chainName cannot be null or empty.");
        }
        Filter filter = getFilter(filterName);
        if (filter == null) {
            throw new IllegalArgumentException("There is no filter with name '" + filterName + "' to apply to chain [" + chainName + "] in the pool of available Filters.  Ensure a " + "filter with that name/path has first been registered with the addFilter method(s).");
        }

        // 将"[]"中的匹配关系注册到filter中
        applyChainConfig(chainName, filter, chainSpecificFilterConfig);

        // 确保chain已经被加到filterChains这张map中了
        NamedFilterList chain = ensureChain(chainName);
        // 将该filter加入当前chain
        chain.add(filter);
    }

至此,FilterChainManager就创建完了,它无非就是缓存了两张map,没有什么逻辑上的操作。下面将FilterChainManager设置到PathMatchingFilterChainResolver中。PathMatchingFilterChainResolver实现了FilterChainResolver接口,该接口中只定义了一个方法:

FilterChain getChain(ServletRequest request, ServletResponse response, FilterChain originalChain);

通过解析请求来得到一个新的FilterChain。而PathMatchingFilterChainResolver实现了该接口,依靠了FilterChainManager中保存的chainFiltersfilters这两张map来根据请求路径解析出相应的filterChain,并且和originalChain组合起来使用。下面具体看看PathMatchingFilterChainResolver中的实现:

   public FilterChain getChain(ServletRequest request, ServletResponse response, FilterChain originalChain) {
        // 得到 FilterChainManager 
        FilterChainManager filterChainManager = getFilterChainManager();
        if (!filterChainManager.hasChains()) {
            return null;
        }

        String requestURI = getPathWithinApplication(request);

        // chainNames就是刚定义的filterChains的keySet,也就是所有的路径集合(比如:["/resources/**","/login"])
        for (String pathPattern : filterChainManager.getChainNames()) {

            // 请求路径是否匹配某个 定义好的路径:
            if (pathMatches(pathPattern, requestURI)) {
                if (log.isTraceEnabled()) {
                    log.trace("Matched path pattern [" + pathPattern + "] for requestURI [" + requestURI + "].  " + "Utilizing corresponding filter chain...");
                }
                // 找到第一个匹配的Filter链,那么就返回一个ProxiedFilterChain
                return filterChainManager.proxy(originalChain, pathPattern);
            }
        }

        return null;
    }

这里返回只有两种情况,要么是null,要么就是一个ProxiedFilterChain。返回null并不表示中断FilterChain,而是只用originChain。而关于ProxiedFilterChain,它实现了FilterChain,内部维护了两份FilterChain(其实一个是FilterChain,另一个是List<Filter>) 
FilterChain也就是web.xml中注册的Filter形成的FilterChain,我们称之为originChain。而另一个List<Filter>则是我们在Shiro中注册的Filter链了,下面看看ProxiedFilterChain中关于doFilter(...)的实现:

 public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
        if (this.filters == null || this.filters.size() == this.index) {
            //we've reached the end of the wrapped chain, so invoke the original one:
            if (log.isTraceEnabled()) {
                log.trace("Invoking original filter chain.");
            }
            this.orig.doFilter(request, response);
        } else {
            if (log.isTraceEnabled()) {
                log.trace("Invoking wrapped filter at index [" + this.index + "]");
            }
            this.filters.get(this.index++).doFilter(request, response, this);
        }
    }

可以看到,它会先执行Shiro中执行的filter,然后再执行web.xml中的Filter。不过要注意的是,需要等到originChain执行到ShiroFilter之后才会执行Shiro中的Filter链。 
至此,两个组件的创建过程差不多都介绍完了,那么当这两个组件创建完毕后,是如何工作的呢? 
先从ShiroFilter入手,因为它是总的拦截器,看看其中的doFilterInternal(...)方法:

  protected void doFilterInternal(ServletRequest servletRequest, ServletResponse servletResponse, final FilterChain chain)
            throws ServletException, IOException {

        Throwable t = null;

        try {
            final ServletRequest request = prepareServletRequest(servletRequest, servletResponse, chain);
            final ServletResponse response = prepareServletResponse(request, servletResponse, chain);

            final Subject subject = createSubject(request, response);

            //noinspection unchecked
            subject.execute(new Callable() {
                public Object call() throws Exception {
                    // 其实需要关心的就在这里
                    // touch一下session
                    updateSessionLastAccessTime(request, response);
                    // 执行Filter链
                    executeChain(request, response, chain);
                    return null;
                }
            });
        } catch (ExecutionException ex) {
            t = ex.getCause();
        } catch (Throwable throwable) {
            t = throwable;
        }

        if (t != null) {
            if (t instanceof ServletException) {
                throw (ServletException) t;
            }
            if (t instanceof IOException) {
                throw (IOException) t;
            }
            //otherwise it's not one of the two exceptions expected by the filter method signature - wrap it in one:
            String msg = "Filtered request failed.";
            throw new ServletException(msg, t);
        }
    }

跟进executeChain(...)方法:

    protected void executeChain(ServletRequest request, ServletResponse response, FilterChain origChain)
            throws IOException, ServletException {
        FilterChain chain = getExecutionChain(request, response, origChain);
        chain.doFilter(request, response);
    }

如何得到FilterChain的呢?如果你认真的看到这里,那么你应该不难想到其中肯定利用了刚才注册的ChainResolver

   protected FilterChain getExecutionChain(ServletRequest request, ServletResponse response, FilterChain origChain) {
        FilterChain chain = origChain;

        FilterChainResolver resolver = getFilterChainResolver();
        if (resolver == null) {
            log.debug("No FilterChainResolver configured.  Returning original FilterChain.");
            return origChain;
        }

        FilterChain resolved = resolver.getChain(request, response, origChain);
        if (resolved != null) {
            log.trace("Resolved a configured FilterChain for the current request.");
            chain = resolved;
        } else {
            log.trace("No FilterChain configured for the current request.  Using the default.");
        }

        return chain;
    }

猜对了~并且也验证了当resolver.getChain(...)返回null时,直接使用originChain了。然后执行返回的FilterChaindoFilter(...)方法。这个过程我们再脱离代码来分析一下:当我们从浏览器发出一个请求,究竟发生了什么? 
这里只站在Filter的层面来分析。服务器启动后,读取web.xml中的filterfilter-mapping节点后组成FilterChain,对请求进行拦截。拦截的顺序按照filter节点的定义顺序,Shiro利用ShiroFilter来充当一个总的拦截器来分发所有需要被Shiro拦截的请求,所以我们看到在Shiro中我们还可以自定义拦截器。ShiroFilter根据它在拦截器中的位置,只要执行到了那么就会暂时中断原FilterChain的执行,先执行Shiro中定义的Filter,最后再执行原FilterChian。可以打个比方,比如说本来有一条铁链,一直蚂蚁从铁链的开端往末端爬,其中某一环叫ShiroFilter,那么当蚂蚁爬到ShiroFilter这一环时,将铁链打断,并且接上另一端铁链(Shiro中自定义的Filter),这样就构成了一条新的铁链。然后蚂蚁继续爬行(后续的执行过程)。

最后附上默认注册的filters:

public enum DefaultFilter {

    anon(AnonymousFilter.class),
    authc(FormAuthenticationFilter.class),
    authcBasic(BasicHttpAuthenticationFilter.class),
    logout(LogoutFilter.class),
    noSessionCreation(NoSessionCreationFilter.class),
    perms(PermissionsAuthorizationFilter.class),
    port(PortFilter.class),
    rest(HttpMethodPermissionFilter.class),
    roles(RolesAuthorizationFilter.class),
    ssl(SslFilter.class),
    user(UserFilter.class);
}

水平有限,写得蛮不容易,看源码加写花了整整2天。希望对大家能有帮助~

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